1920-1980: The evolution of oxygen delivery devices

By the mid 1920s many of the challenges of oxygen therapy had been tackled.  Oxygen could be easily produced, stored in tanks, and delivered to the patient.  There also existed the means of confirming oxygenation status of patients, and the effects of oxygen therapy.  So the stage was set for oxygen to be introduced to hospitals.

In 1922 John Haldane wrote about his research in "The Therapeutic Administration of Oxygen."
Soon thereafter oxygen tanks became more and more common at the patient bedside.  The tanks were stored in closets, and when needed were strapped by the patient bedside.

There were various devices available for providing oxygen, which included a metal nasal cannula, a nasal catheter, the oxygen chamber, the Haldane Apparatus, and the oxygen rebreather mask or mouthpiece and an oxygen tent.  For patients that were comatose, any device needed to provide therapeutic oxygenation could be used.  For awake and alert patients, the mask posed a claustrophobic feeling, and it was also hot.  The same was true with the oxygen tent.  So the physician would basically have to base what oxygen device he used on the patient.

One of my readers at my Respiratory Therapy Cave blog informed me that, the first practical oxygen tent was invented by Doctor Benjamin Eliasoph in 1921, at The Mount Sinai Hospital,New York, with rubberized fabric from the Goodyear Rubber Company, Aeronautical Division used for balloons such as the widely known Goodyear Blimp." 

This information is confirmed in a New York Times obituary for Dr. Benjamin Eliasoph, which notes: "Dr. Benjamin Eliasoph, a physician at Mount Sinai Hospital who was a pioneer in the design of the oxygen tent, died Sunday at the hospital. He was 70 years old."

The first mass producible oxygen tent was invented by Doctor Leonard Hill.  It consisted of a canopy with slots so the patient could see out that was placed over the bed and patient, and a machine was set at the bedside that blew oxygen into the tent and over the patient.

Dennis Glover, in his 2010 book "A History of Respiratory Therapy," said there was no means of cooling the atmosphere inside these tents, and being inside was almost unbearably hot and uncomfortable for many patients.

Glover said that the most common use for the oxygen tent was for patients presenting with cyanosis due to heart failure or pneumonia.  Some patients would beg to get out of the tents, Glover explained, yet once out they would became short of breath and they'd beg to get back in.  So it was sort of a double edged sword for the patient until the patient got better, if they got better.  Some critics complained such tents basically provided a tortuous method of ending a person's life, and petitioned for their demise.

In 1926 Alvin Barach invented an oxygen tent that blew air over ice chips to cool the temperature inside the tent.  This made it so being inside the tents was much more bearable.  Usually these they were reserved for patients with pneumonia and heart failure. (2)

In 1931 John Emerson invented an oxygen tent that had a cooling system.  Previous devices were prone to rust and failure.  (7)

The metal cannula was another device that was used.  It was a narrow metal pipe that was secured to the forehead by a strap that wrapped around the head, and at the lower end of the pipe were two prongs that were inserted into the nares.  I can imagine this may have felt awkward for the patient, but it may have been much nicer than having to lie inside an oxygen tent or having a rubber mask on your face.

The nasal catheter was introduced to the world by Lane in 1907, and introduced to the United States in 1931 by Waters and Wineland. (3)  Between 1920 and 1960 the nasal catheter was the most widely used method of delivering oxygen to patients. (8)

Glover explained that by the 1960s vinyl had been invented and this technology spread to the medical profession.  Masks, catheters, nasal cannulas and tubing were then made of this new material, and were much more comfortable for patients.  (2)
l
Another benefit was the material was see through, and this allowed the caregivers to see right away if the mask was filling with secretions, vomit or pulmonary edema. This made the masks much safer. They were also disposable, so it removed the need to clean and sterilize between patients.

Vinyl nasal cannulas quickly became the preferred basic oxygenation device, and this slowly caused the demise of the nasal catheter.

The nonrebreather was also introduced during the 1920s.  For those not familiar with these, they involve placing a mask tightly over the patients face to prevent the entry of room air. A one way valve on the mask allows the patient to exhale, but it closes on inhalation. This forces the patient to inhale only oxygen, which enters the airway from tubing which is connected from the mask to an oxygen flow meter. A bag connected to the mask collects oxygen while the patient is exhaling. When the patient inhale, inhales oxygen that is stored in the bag.

It is called a nonrebreather because the patient is not rebreathing any exhaled air. The idea here is that, if there is that if the mask is sealed tightly around the patient's face, and the one way valves are working, then the patient should be inhaling 100% oxygen.

Of course a problem with this system is that there were no surefire methods of knowing how much oxygen was left in an oxygen tank. So when a tank became empty, the patient had not oxygen to inhale, and would die of asphyxia. Learning this the hard way must have given quite a fright to some early orderlies, nurses and doctors.

The remedy to this problem was to remove one of the one way valves to assure that, if the oxygen tanks to run empty, that the patient can still inhale some room air. This is how most nonrebreather masks are produced today. So, while some people still report that nonrebreathers give patients 100% oxygen, the actual percentage is estimated to be between

Nonrebreathers of today aren't even nonrebreathers at all: they are partial rebreathers. Still, it is very common for them to be called nonrebreathers. They aren't generally referred to as partial nonrebreathers until both one way flaps are removed. With both flaps removed, the patient's estimated FiO2 is about 50-60%.

This represents one of the medical conundrums in medicine.

Early masks were also not see through, so if a patient vomited you might not know right away. Newer masks are made of disposable material that is see through, eliminating some of the older complications from these masks.

Regardless, nonrebreathers were good devices for oxygenating patients suffering from acute anoxia.

The next evolutionary breakthrough in oxygen delivery devices came as a result of observations made during the 1950s that some patients given 100% oxygen were becoming lethargic. It was soon realized that these were patients with emphysema and chronic bronchitis, or what we now refer to as chronic obstructive pulmonary disease (COPD).

This was where the hypoxic drive theory was derived from. You can learn about this theory in my post, "Hypoxic Drive Theory: A History of the Myth."  Essentially, this theory postulates that giving too much oxygen to some COPD patients might blunt their drive to breathe. So this resulted in the market for a better oxygen delivery device, and the invention of the Venturi Mask.

The new masks were based on the Venturi Principle, and allowed physicians the opportunity to provide accurate oxygen levels up to 50%. Nasal catheters, and later cannulas, were the preferred method of oxygenating these patients. However, because these devices are low flow devices, changes in the rate and depth of breathing make these less effective. Venturi masks were nice because they guaranteed the patient would get the desired oxygen level.

This was because the masks were based on the Venturi Principle. An adjustable opening allowed the caregiver to determine how much air was being inhaled. The larger the opening, the more air was inhaled and the less oxygen inhaled. The smaller the opening the less air was inhaled and the more oxygen was inhaled. So oxygen could now be set at between 28 and 50%, and this would not be affected by changes in rate or depth of breathing. It was a nice concept, especially for COPD patients.

These masks are still used today as a nice option for patients who are in respiratory distress, or who need a little more oxygen than a nasal cannula can provide, but don't quite need anything higher than 50%. They are generally only made as a temporary oxygen device, although some patients with terminal lung diseases (such as lung cancer) may occasionally use one at home.

By the 1980s plastic had been invented, and during this decade most respiratory therapy devices were slowly replaced by plastic.  Plastic nasal cannulas, masks, and nebulizers were introduced in the early 1980s and slowly phased into various hospitals through assimilation.

The earliest oxygen humidifiers were either made of metal or glass.  Until plastic was invented, none of the equipment here was disposable, and needed to be washed, sterilized, dried, and restocked on the shelves before being set up on the patient. So cleaning respiratory therapy equipment became sort of a secondary job for therapists until this aspect was phased out by turn of the 21st century.

References:

1. Hess, Dean,  Neil MacIntyre, Shelley Misha,"Respiratory Care:  Principles and Practice," page 281
2. Glover, Dennis, "History of Respiratory therapy: discovery and evolution, ," 2010, Indiana, page 94
3. Wyka, Kenneth A., Paul J. Mathews, John Rutkowski, editors, "Foundations of Respiratory Care," 2012, U.S., Delmar, page 9
4. Hess, Dean,  Neil MacIntyre, Shelley Misha,"Respiratory Care:  Principles and Practice," page 281
5. Barach, Alvin L., "The Therapeutic Use of Oxygen," The Journal of the American Medical Association, Vol 79, No. 9, Chicago, October 26, 1922, page 693-699
6. Barach, Alvin L, Margaret Woodwell, "Studies in oxygen therapy with determinations of blood gases," Archives of Internal Medicine, Vol. 28, 1921, Chicago, American Medical Association, pages 367-393
7. Branson, Richard D, "Jack Emerson:  Notes on his life and contributions to Respiratory Care," Respiratory Care, July 1998, vol. 43, no. 7, pages 567-71

Further Reading:

1. Use of oxygen in pneumonia in an oxygen chamber, page 466
2. RT Cave: Oxygen Therapy Made Easy
3. RT Cave: ypoxic Drive Theory: A history of the myth
4. RT Cave: The Physics Lexicon

1910-1920: The oxygen revolution

Joseph Barcroft (1872-1947)
In 1886 he received his M.D. from Cambridge,
and began his study of hemoglobin.
He exposed himself to different environments
to determine their effects on the human body.
.

Three significant events occurred at the dawn of the 20th century that resulted in increased interest in supplemental oxygen therapy. The first was the invention of a means of measuring oxygen saturation. The second was an experiment that Dr. Joseph Barcroft performed on himself. The third were experiments by WWI physicians to find a treatment for pulmonary edema caused by gas poisoning.

The ability to draw arterial blood was a significant discovery. It was hurter in 1912 who introduced the method. (2, page 693)

Yet even more significant was the machine blood could be inserted into that would determine the how saturated hemoglobin molecules in the blood were with oxygen molecules. This is referred to as oxygen saturation. Once inserted into the machine, the saturation was reported as a percentage.

John Scott Haldane (1850-1936)
He graduated from Edinburgh University in 1884,
and worked with his uncle at Oxford,
where he became interested in air,
its composition, and effects on humans.

Adolf Fick of Germany and Paul Bert of France described oxygen tensions as units of partial pressure, and it was these units that made it possible to describe the difference between arterial and venous blood. Since the partial pressure of oxygen in arterial blood is higher than the partial pressure of oxygen in venous blood. Or at least this is the case in a healthy individual. (1, page 4) (2) (6)

Donald Dexter Van Slyke (1883-1971) and John Scott Haldane (1892-1964) of Scotland developed effective means of measuring these differences. (1, page 94) (2) (6)

Further studies by various experts determined the normal levels and critical levels of oxygenation. It was determined that a normal arterial saturation of hemoglobin is between 95 and 98 percent, and a normal venous saturation is between 70 and 75 percent. These new values allowed physicians to monitor a patient's oxygenation status, and the effectiveness of oxygenation therapy. (2)(3, page 369)

Among the first to prove the significance of this discovery was Sir Joseph Barcroft, who lived for six days in an atmosphere that had 18 percent oxygen in the air, as opposed to the normal 21 percent that's in roomair. Alvin L. Barach, a pioneer in oxygen therapy, liked to use Barcroft's experiment as an example to prove the significance of oxygenation.

Barach explained:

"On the last day, the oxygen saturation of his arterial blood was 88 per cent., and after the performance of work 83.8 per cent. He lay in the chamber racked with headache, with occasional vomiting, and at times able to see clearly only as an effort of concentration. He became faint on exertion. His pulse, normally 56, had risen to 86. These effects were apparently due purely to oxygen want. The degree of anoxemia that produced them has frequently been found in pneumonia and heart disease by the investigators mentioned above. In many instances, the saturation of the arterial blood falls to far lower levels. It would, therefore, seem likely that lack of oxygen in the degree often found in disease would produce bodily discomfort, disturbances in function and damage to living structure." (3, page 369)

The effects on Barcroft were similar to the effects of pneumonia and heart failure for some patients. Studies showed that the oxygen saturation could range from 75-95 percent in cases of cardiac insufficiency, and 60-95 percent in cases of pneumonia. (2, page 693)

So it became apparent these diseases, as they progress, decrease the amount of oxygen that gets to the blood and to hemoglobin.  

Various studies, including the Barcroft study, proved that a low level of oxygen stimulates the central nervous system to stimulate various changes within the body in an attempt to return oxygenation back to normal: heart rate increases, respiratory rate increases in rate but decreases in depth, patient may become delirious and may have hallucinations  If not treated, death may result.  (2, page 694)

So these studies proved to the medical community the significance of observing the signs and symptoms of poor oxygenation and speedily treating them with oxygen. (2, page 694)

Oxygen was not meant to cure, but to treat the symptom of low oxygenation long enough to allow the physician to remedy the underlying condition, which may include: (2, page 694)

• Pneumonia
• Acute Cardiac Failure
• Severe Hemorrhage
• Epidemic Encephalitis
• Ascent to high altitudes
• Complications of chronic cardiac insufficiency
• Pulmonary Edema
• Acute Bronchitis
• Carbon Monoxide Poisoning
• Nitrous Oxide Poisoning
• Other anesthesia

Further studies also allowed physicians the opportunity to determine that a therapeutic percent of oxygen for most diseases was between 40 and 60 percent, and it's for this reason the oxygen chamber, oxygen catheter, and nasal cannula generally are not effective for oxygenating patients with severe oxygen deprivation. (2, page 696)

Studies likewise showed greater than 70 percent could cause pneumonia, and did so in rabbits. (3, page 373)

It was probably based on these and similar studies that John Haldane, another pioneer of oxygen therapy, would recommend 41% oxygen administration continuously for patients suffering from anoxemia (Haldane would coin a new term to describe this: hypoxemia). (6) (7) (8)

In fact, it is said Haldane once mused:

Intermittent oxygen therapy is like bringing a drowning man to the surface of the water—occasionally. (7) (8)

Yet even while he and other physicians proved the usefulness of continuous oxygen therapy during WWI, it would take a few more years for it to catch on. (6)

Oxygen mask designed by Haldane in 1917

A third significant event was the gas poisonings that occurred during WWI. Phosgene was used by the enemy on the war front because, when it combines with water in the lungs, it creates hydrochloric acid, which damages lung tissue. If inhaled in high enough doses it may cause pulmonary edema within 6-10 hours, leading to acute respiratory distress syndrome (ARDS).  As the illness progresses, the lungs lose their ability to pass oxygen to pulmonary capillaries, therefore causing anoxemia or hypoxemia. (6)

While oxygen was not thought to cure these patients, it was believed that it would treat the symptoms caused by anoxemia, particularly cyanosis and dyspnea.

Sometimes patients who presented with pulmonary edema due to gas poisoning were treated in oxygen chambers, which could be supplied with 40-60 percent oxygen. These chambers were found to be effective in treating cases of chronic gas poisoning. Some patients would spend up to 16 hours a day inside one with good results. (3, page 360)

However, this therapy wasn't practical for common use.

Another means of providing these patients oxygen was to use a tube or funnel to aim the oxygen at their faces, although studies showed this provided no more than a 2 percent increase in oxygenation of inspired air.

So this opened the door for an improved oxygenation apparatus that was easily portable by medics, comfortable to wear, could be used long term for chronic cases, and provided a therapeutic dose of oxygen. John Haldane invented such a device, and it was called the "Haldane Apparatus." (3, page 370)

Alvin Barach said Haldane's apparatus provided oxygen blended into the air the patient inspired, and by doing this the amount of oxygen making it to the alveoli was greatly increased. By this means, the patient was supplied with a therapeutic level of oxygen. (3, page 370)

Barach described the device as consisting of an oxygen tank, a reducing valve, and a face mask. He said:  (3, page 370)

"The mask was connected with a connecting bag which received oxygen from the tank, and with the outside air, from which the patient breathed. Oxygen was added to the inspired air in amounts of from one to four liters per minute. This was largely used in acute cases with generally good results." (3, page 370)

The problem with the Haldane apparatus was the only patients who tolerated it were those who were comatose. It worked great for these patients. Yet for others, for those who were awake and alert, it was not comfortable. Patient's complained that having the mask over their faces created a feeling of claustrophobia, and the mask was also hot and stuffy. This was especially a problem on hot days. Some patients simply didn't tolerate the mask, and some even ripped it off, refusing to wear it. (3, page 370)

Another problem, a pretty severe one actually, was it was impossible for clinicians to see through the opaque rubber masks. Clinicians learned to be vigilant, although this sometimes didn't prevent them from getting busy and not recognizing a patient was vomiting or expectorating foaming pulmonary edema. When not recognized, secretions occluded airways resulting in worsening anoxemia.

This concern opened the door for a more comfortable and safer oxygenation device.

One such device was the nasal cannula or prongs devised by Captain Adrian Stokes, M.D., in 1917. Stokes created the device while triaging patients on the war front who were suffocating due to pulmonary edema, and to which the tight fitting rubber mask of Dr. Haldane was not feasible. The metal cannula provided less oxygen than Haldane's device, although it helped medics keep pulmonary fluid from re-entering and blocking the airway. (1, page 38) (3, page 370)  (5, page 8) (6)

Stoke's cannula was a device similar in design to what we use today, although it was supplied by rubber tubing and the prongs were made of metal, and therefore was not very comfortable. However, patients tolerated it much better than the rubber mask, and of course it was safer. (1, page 38) (3, page 370)  (5, page 8) (6)

A similar device was the rubber nasal catheter, which was initially invented by Arbuthnot Lane in 1907, although re-introduced by Stokes in 1917. The catheter was introduced into the United States in 1931 by Waters and Wineland.  (1, page 17) (5, pages 8-9) (7, page 20)

The soft, rubber catheter (later made of pliable plastic) was a 12 inch long tube that was blindly inserted into one of the nostrils and then secured to the forehead. The patient would then open his mouth, depress his tongue to the bottom of his mouth, and the physician or nurse would check to see that the catheter was in place at the back of the airway. (4)

The end that remained outside the patient had a fitting to which oxygen supply tubing was connected.  On the distal side of the catheter, the side inside the patient's airway, were a series of small holes to allow oxygen to enter the patient's airway.  (4)

Catheters were designed for adults and pediatrics, the flow was set at 1- 5 lpm, and the the delivered oxygen was 22-35%.  The catheters would stay in the nose for a day or two.  If it was needed longer a new catheter had to be inserted. (4)

Most experts recommended changing the catheter every 24 hours to prevent tissue breakdown, and most hospital protocols eventually called for changing it every eight hours.

So you can see that while it was more convenient for the patient, there was some risk to the patient too.  It also provided some inconvenience for those taking care of patients requiring it.

While nasal catheters were simple to insert and manage, and while they were generally well accepted by patients, they did not provide enough oxygen in patients presenting with acute pulmonary edema or worsening pneumonia to eliminate cyanosis.  (3, page 370)

The nasal catheter was the most commonly used device for supplying supplemental oxygen prior to the invention of the modern nasal cannula in the 1960s.

Figure 2 --Apparatus for giving oxygen.(3, page 374)

Another option was a device similar to the one in figure 2.  The apparatus works this way: 

"The patient breathes through the rubber mouthpiece M (or a mask could be used) through the can of soda-lime C into a rebreathing bag B. The carbon dioxide exhaled is removed by the soda-lime, and oxygen is admitted from the tank O at a sufficient rate to keep B inflated.In this way the patient rebreathes pure oxygenfrom the apparatus,but since his nose is left open he dilutes this with a certain proportion of atmospheric air. In practice this results in the inhalation of from 40 to 60 per cent, oxygen." (3, page 374)

Yet another option was the oxygen tent. These were clear canopies that were made to cover the entire bed. A machine at the bedside provided an environment inside the tent of about 30 percent oxygen. These were effective as far as oxygenating some patients, although the original oxygen tents were hot and stuffy, and this particularly posed a problem on hot days.

Patients would generally go inside one long enough to catch their breath, and then they'd return to breathing room air. (1, page 94)

Barach recommended to physicians that the best means of measuring oxygenation status was by monitoring the heart rate, respiratory rate, and especially the level of cyanosis (bluish skin color). This was much more logical than an invasive blood draw. (3, page 370)

Caregivers would ultimately learn to monitor these signs, along with level of consciousness, before, during and after therapy.  This, they found, was the best means of monitoring the effectiveness of oxygenation therapy, and whether or not it was still needed.  (2)

What equipment to use to supply oxygen depended on what equipment was available, the physician taking care of the patient, and the independent oxygenation requirements of patient.

How long oxygen therapy was used primarily depended on the patient and how quickly, or slowly, the underlying condition resolved. (2)

Still, by 1922, when Barach wrote many of his papers, he explained that...

"the use of oxygen in medical therapy occupies at present an uncertain role." 

Despite Barach's doubts, the 1920s was an oxygen revolution of sorts.

Barach would go on to study the effects of oxygen therapy on a variety of respiratory diseases, including pneumonia and cor pulmonale. He would also study the effects of oxygen therapy on respiratory failure. For his work, he is often considered the father of modern oxygen therapy.

References:

1. Glover, Dennis, "History of Respiratory therapy," 2010, Indiana, page 94.
2. Barach, Alvin L., "The Therapeutic Use of Oxygen," The Journal of the American Medical Association, Vol 79, No. 9, Chicago, October 26, 1922, page 693-699
3. Barach, Alvin L, Margaret Woodwell, "Studies in oxygen therapy with determinations of blood gases," Archives of Internal Medicine, Vol. 28, 1921, Chicago, American Medical Association, pages 367-393
4. Hess, Dean,  Neil MacIntyre, Shelley Misha,"Respiratory Care:  Principles and Practice," page 281
5. Wyka, Kenneth A.,  Paul Joseph Mathews, William F. Clark, editors, "Fundamentals of Respiratory Care," 2002
6. Grainge, CP, "Breath of Life: the evolution of oxygen therapy," Journal of the Royal Society of Medicine, October, 2004, 97 (10), pages 489-493
7. Heffner, JE, "The story of oxygen," Respiratory Care, January, 2013, volume 58, number 1, pages 18-30
8. Sekhar, KC., "John Haldane: The Father of Oxygen Therapy," Indian Journal of Anesthesia, May-June, 2014, 58 (3), pages 350-352

1983: The mist tent and the nice respiratory therapist

It was 1983. I went to the emergency room for bad asthma. I was given the Sus-Phrine shot and rolled up to a room behind the nurses station. My asthma episode was really bad. So, doctor Oliver wanted me right by the nursing station. So, they put me in a room literally right behind the station.

There was a window where I could watch the nurses. I hated it. There was no privacy. I was actually stressed that I wouldn't be able to change without a bunch of female nurses watching me. But, after the first night, after I was feeling better, the doctor said I could have the curtain pulled. This was nice.

I was kind of a claustrophobic kid. When I was in Kintergarden and first grade, I remember we had to wear hats and snow suits. I hated this. I felt like I couldn't breathe when I was all bundled up like that. The teachers hated it that I was not compliant. But, ultimately, what choice did they have but to let me go out without them on.

Okay, the same thing with nasal cannulas. Here I was struggling to breathe for hours before I went to the emergency room, and that last thing I wanted was something over my face. I would get a breathing treatment, I would get the shot, and at some point someone would say, "We better put oxygen on him."

I would pull it off. They would put it on. I would take it off. They would put it on. I would take it back off. I remember this happening often. And, I don't ever remember anyone ever giving me a hard time about it. It probably bothered them, as I imagine I appeared cyanotic at times, but it never bothered me. All I wanted was the shot. I knew the shot would make me feel better. I didn't need something on my face.

So here I am, sitting in this room behind the nurses station. Mom is reading to me. I'm feeling soothed. And the doctor comes in. He says something about a mist tent. I wasn't thrilled about it. And I wasn't upset when it was several hours before a respiratory therapist came in and said, "It will be like being in a tent."

I wasn't thrilled, but I didn't feel like fighting. I knew that reason was because I refused to wear a cannula. And, I suppose, I must have been cyanotic. However, based on the fact the therapist appeared to be dragging his feet with setting it up, I highly doubt I was cyanotic. It was probably just some stupid idea my doctor got. I know how doctors are now that I have been working with them 20 years. Sometimes they just feel as if they have to do something, even if that something is something that's not needed.

Okay, so I ended up in this tent. The TV was on. I could hardly see the TV through the wrinkled plastic that was over my bed. Okay. It was nice and cool in it, however. Mom was sitting next to my bed. She may have read to me. But then my dinner came. I wasn't even in the tent for an hour, and I was allowed out to eat. I never went back in.

Later that night a really nice therapist came into my room. There usually wasn't a therapist on night shift. But tonight there was. She came in around 8 p.m. to give me a breathing treatment. She talked to me for hours. She was so nice. She told me I didn't have to go back into that tent. I was so happy. Before she left, I said, "Make sure you wake me up tonight for my treatments." She said, "I will."

She never did.

Fast forward 25 years. My coworker is Joella. I came into work one day and she said, "A memory occurred to me this morning. I was working in Manistee part time. I was called in to work because they had a 10-year-old asthmatic in a mist tent. A thought occurred to me: It was YOU."

She was right. Her name was Joella. She is now retired and living the good life.

This experience inspired a post at healthcentral.net, along with the following comic.

1830-1900: Early ventilators and intubation devices

Figure 1 -- Bouchut's Endotracheal Tube
(23, page 6)

If you are a physician, nurse, or respiratory therapist you can skip the next couple paragraphs. For the rest of my readers, I would like to take a moment to explain about breathing and artificial breathing. I want to explain about ventilators and intubation.

Obviously, in order to stay alive people must continue breathing. By 1830 physicians were well aware of this fact. This was important for victims of near drownings, and for patients who required anaesthetics during complicated surgeries. During these times, some method of artificial resuscitation was required, or some means of breathing for the these patients, at least until they regained their ability to spontaneously breathe.

How do people inhale? Natural inhalation occurs when the muscles of inspiration constrict, thus pulling the chest wall outward. This creates a negative pressure inside the chest resulting in air being drawn (sucked) into the lungs.

How do people exhale? Natural exhalation occurs when the muscles of inspiration relax, thus causing the chest wall to naturally recoil. This creates a positive pressure inside the chest resulting in air being forced out of the lungs.

Figure 5

Negative Pressure Ventilators mimic the natural means of inhaling. The patient is placed inside a tank that creates a negative pressure that draws the chest outward, thus causing inhalation. The problem with these machines is that they made it so that it was difficult to gain access to the patient. This problem was resolved with positive pressure ventilation.

Positive pressure ventilation essentially involves forcing inhalation by creating a positive pressure. The most primitive, and most basic, form of positive pressure ventilation is mouth to mouth breathing. Another mean is to provide positive pressure by using a mask. A modern name for this is noninvasive positive pressure ventilation, although this term would not be introduced to the medical profession for another 150 years.

By the 1830s, the medical profession was well aware of the importance of breathing. They had some methods of manual resuscitation, although most of these required more than one person to perform, were time consuming, and were exhausting. None could be performed for any length of time.

An added concern of these methods is that they involved moving the patient's arms and legs, risking injury to the body. They also did not guarantee that a patient was receiving an adequate tidal volume. So the need arose for some mechanical apparatus to provide artificial resuscitation.

That said, the need had arisen for a mechanical apparatus to provide, or at least assist, with artificial resuscitation. Ideally it would be something that would eliminate the risk of breaking arms and legs, would provide an adequate tidal volume with a low pressure, and would reduce or eliminate the need for manual power.

1832:  Dalzeil respirator:  In 1832, Scottish physician John Dalzeil described what many refer to as the precursor to negative pressure ventilators that would follow, including the Woillez Iron lung which is described below. (16)  It was essentially the first known example of noninvasive negative pressure ventilation.

It was a box, and he once used it to ventilate a man who was a near drowning victim.  The patient sat up while in the box with his head and arms outside the box.  The box was airtight, and bellows inside caused a negative pressure that caused inspiration.(16)

A window on the outside of the box allowed an observer to see if it was actually causing respirations.  This is often referred to as the first tank respirator, or the first iron lung.  The box had to have been hand powered, and there is no documentation it actually worked.  (16)

1845:  Oxygen breaths  Of course another thing that physicians learned early on was the importance of making sure a patient is getting enough oxygen while artificial breaths were being performed. A man named Erichson invented the first device that provided positive pressure breaths with oxygen through a cannula inserted through a pipe inserted into one of the nostrils.  He recommended ten breaths a minute.

Figure 4

1858:  Bouchut's Intubation Tube:  The noninvasive methods of providing positive pressure ventilation were not effective long term.  The negative pressure ventilators were fine, although they usually consisted of large, bulky tanks that made gaining access to the patient difficult. So another means was needed to provide artificial resuscitation long term. 

So this inspired early experiments with inserting hollow tubes into the airway.  This is considered to be invasive. So, from here on out, anytime a person needs to have a tube inserted into their airway to provide resuscitation, it is referred to as invasive ventilation. 

Earlier physicians tried using a catheter, but this wasn't very effective. In 1858, French physician Eugene Bouchut (1841-1898) became the first to describe insertion of a tube into the airway as opposed to a catheter in a case of dyspnea. The tube he used during seven cases between 1856-1858 (24, page 661-662) was a rounded silver tube narrower at the end to be inserted as you can see in Figure 1, and it was 1.5 to 2 cm long and 7 cm in diameter.

Interestingly, a silk thread was attached to the distal end of the tube that was "brought out to the mouth, and was intended to prevent the tube from going down the trachea or esophagus; and to allow it to be taken out when necessary." 

He later "insisted on the distinction between his method and catheterism." However, of the seven cases he cited to the French Academy of Medicine, only two lived and both required tracheotomy.  Yet he proved the procedure could be done. 

Various other physicians described success with this or similar procedures between 1858 and 1880 when Joseph O'Dwyer (see below) introduced a more effective tube. (see figure 1)(23, page 5)

1867:  Richardson's Double Acting Rubber Bellows:  Benjamin Ward Richardson created a bellow system similar to Hunter's Bellows (although he may not have known of Hunter's Bellows). The original system took up a lot of room, so he invented the double acting bellows, which "consists of two rubber bulbs terminating in common tube that was called the nostril-tube."  One bellow supplied inspiration, the other expiration.  (See figure 4)

1875:  Blake cures poison victim:  Using a device similar to Richardson's Bellows, Blake connected a reservoir of condensed oxygen to it and treated a case of acute poisoning with success.  Before this time artificial respiration (often referred to as insufflation) was used mainly to treat neonatal asphyxia, but now the focus was also on treating adults.  The nozzle of the device was inserted into the nostril.  

1876:  Woillez Iron Lung (Spirophone): While the iron lung wasn't mass produced until the late 1920s, there were some earlier models that acted as prototypes of later designs.  In fact, the design described by Woilliz was quite similar to the Drinker and Shaw and Emerson iron lungs.  The only drawback to Woillez's design was he didn't have access to electricity, so his machine was powered by hand.

At the French Academy of Medicine in Paris in 1876 Woillez described his respirator this way:

"(The apparatus is) a zinc or sheet iron cylinder large enough to receive the body of an adult up to the neck. It is equipped with wheels which permit moving it rapidly to the place where it is necessary. The cylinder set almost horizontal slightly inclined is hermetically closed at the boot end and open at the head end. Through this opening at the head end you slide the body of the patient by means of a sort of stretcher equipped with rollers, on which he is previously placed; then you close the head opening around his neck by means of a diaphragm that you attach to the edges of the opening. The head thus remaining free rests on an appropriate support. A flexible impermeable fabric attached to the cover diaphragm is secured around the neck to avoid as far as possible the passage of exterior air to the inside of the apparatus, at the moment when the vacuum is produced there.

The air thus confined in the apparatus around the body of the patient can be partially rapidly withdrawn by means of a powerful aspirator bellows of about 20 litres capacity actuated by means of a lever. The interior of this pump communicates with the interior of the apparatus through a large tube tightly screwed on." (17)

There were other similar designs, yet none became mass producible mainly due to lack of knowledge of electricity at the time.

O'Dwyer's Intubation Tube for a child 2-3 years old (23)

1880:  The first useful endotracheal tube:  Dr. Joseph O'Dwyer (1841-1898) of New York, and his fellow physicians at the New York Foundling Asylum, observed problems with trachetomy.  He decided another means of breathing for patients was necessary, and he at first trialed flexible catheters into the nasal passages.

Yet this didn't meet his satisfaction so he devised a tube to be placed into the larynx where it would remain.  By trial and error he tinkered with the device until it met his satisfaction.  The device was made with a bivalve tube with a narrow transverse diameter, and about an inch long."

A shoulder on the upper end prevented the tube from slipping down.  By trial and error the tube transformed so the tube was a "plain tube of elliptical form about an inch in length."  He then played with longer tubes until he found the desired length.  The final tube used was made of brass and lined with gold, and was accepted by the medical community.  (See figures 2 and 3.)

A complete set was included in a box, that included sizes for different aged children, an obturator, an introducer, an extractor, and a gag.  The length of the tubes in inches were 1.5, 1 3/4, 2, 2.25 and 2.5.   The obturator of the physicians choice is connected to the end of the introducer, and this is used to insert the tube.  If necessary a small thread could be inserted and tied to a hole on the outer edge of the tube to prevent it from going down the trachea, and to facilitate removal.

The kit also came with a scale (see figure  5) which helped the physician determine appropriate depth of the tube according to age.  The scale is used like this: "The smallest tube reaches line 1, and is intended for children about one year and under. The next reaches line 2, and is for children between one and two years. The third size, marked 34 on the scale, should be used between two and four years. The fourth, marked 5-7, is for the next three years, and the largest tube is for children from eight to twelve."

O'Dwyer also designed larger tubes and equipment for adult intubation. (23, page 9-18)

O'Dwyer's introducer connected to obturator (23, page 16)

1888:  Foot operated Bellows

Dr. George Fell invented a system of bellows whereby the operator would use his hands to provide positive pressure breaths.  He would either use a tracheotomy or face mask.  In 1891 this system was revised by Joseph O'Dwyer of New York so that breaths were provided by pressing down on a lever with your foot.  O'Dwyer preferred to connect his bellow system to an endotracheal tube.  O'Dwyer was concerned about over-distention of the lungs due not allowing enough time for expiration, and therefore recommended giving slow breaths, or 10-12 per minute. (21, page 283)

1891:  Concerns of Intubation:  By the late 19th century many of the same concerns physicians have today about intubation were considered.  One such concern being the ulceration of tissue due to pressure of the tube set upon it for a long period of time.  Tubes were generally taken out after six days with success, although in some cases were left in 12 days or longer. Dr. Rank, a German physician, ultimately recommended removal of the tube after 10 days, and if necessary, the physician should consider tracheotomy.

Some physicians recommended extubation after the 5th day, which would be in line with modern protocols. Feeding the patient was also a concern, and was either done with soft foods or liquids, or by nasalgastric tube.  It was recommended that if the tube was accidentally spit up that the nurse take advantage of the moment to try feeding the patient prior to re-introducing the tube (if the tube was still needed). (23, page 29-20)

1898 Matas's Apparatus for Artificial Respiration:  Around this time the need arose for a means to prevent asphyxia when chloroform was used. There was also the concern of preventing pneumothorax during artificial respiration.  Matas deviced the "experimental automatic respiratory apparatus" as you can see in figure 4.  

This was never put in use on a real patient, and was mainly used to study the effects of pressure during inspiration and expiration.  You can see some of the major components in the picture: MF = O'Dwyer intubating cannula and stopcock for introducing chloroform; M = Mercurial manometer to measure pressure or vacuum; H is the handle to work the pump and forces air into the lungs. The operator placed a finger over a hole in the O'Dwyer intubation cannula, and when he removed his finger expiration occured.  (R = Rubber tubing.)

It was quite a contraption for its time. Experiments were performed on dogs and human cadavers, although it was decided it was not fit for use on humans. (See figure 4) (21, page 284)

Figure 4 (21)

1900:  Cuffed Endotracheal Tubes and laryngoscopes

Right around the turn of the century was when the furst cuffed endotracheal tubes (ETT) started showing up.  This was necessary to prevent air from leaking around the tube so that bigger breaths could be given, and it also worked nice to prevent aspiration around the tube. 

Another problem was how to insert the tube into the ETT into the airway. Blind insertion meant there was a risk of intubating the esophagus, which, if not recognized, resulted in asphyxia and death. 

A laryngoscope is a device that allowed the doctor to open the airway in order to see the vocal cords and glottis. This increased the likelihood of tracheal intubation. 

A larygoscope was first described in 1855 using sunlight to see the vocal cords, and by 1913 a battery powered laryngoscope with an external light was invented.  This was refined so it had a handle with a battery and a light bulb at the end of the scope for easy visualization of the vocal cords.   (18)

Related posts:

• 4000 B.C. - 1800:  Evolution of Artificial Respiration
• 1800-1900:  The Beginning of Pressure Therapy
• 1800-1900:  The Beginning of Pressure Therapy (part II)

References:

1. Szmuk, Peter, eet al, "A brief history of tracheostomy and tracheal intubation, from the Bronze Age to the Space Age," Intensive Care Medicine, 2008, 34, pages 222-228
2. Price, J.L., "The Evolution of Breathing Machines," (this must have been written in the 1950s or early 1960s because the last reference was to IPPB being used as a respirator) (reference to The Bible, Kings, 4: 34)
3. Tan, S.Y, et al, "Medicine in Stamps:  Paracelsus (1493-1541): The man who dared," Singapore Medical Journal,  2003, vol. 44 (1), pages 5-7
4. "Resuscitation and Artificial Respiration," freewebs.com, Scientific Anti-Vivisectionism,  http://www.freewebs.com/scientific_anti_vivisectionism4/resuscitation.htm, accessed March 1, 2012
5. Price, op cit
6. Lee, W.L., A.S. Stutsky, "Ventilator-induced lung injury and recommendations for mechanical ventilation of patients with ARDS," Semin. Respit. Critical Care Medicine, 2001, June, 22, 3, pages 269-280
7. Price, J.L., "The Evolution of Breathing Machines,"  (see also reference #1 and #3 above)
8. Szmuk, op cit, page 225
9. Price, op cit
10. "Resuscitation and Artificial Respiration," freewebs.com, Scientific Anti-Vivisectionism,  http://www.freewebs.com/scientific_anti_vivisectionism4/resuscitation.htm, accessed March 1, 2012 (see also reference 1 above)
11. Lee, op cit
12. Price, op cit
13. Price, op cit
14. Szmuk, op cit, page 225
15. Price, op cit
16. Woollam, C.H.M., "The development of apparatus for intermittent positive pressure respiration," Anaesthesia, 1976, volume 31, pages 537-147
17. Previtera, Joseph, "Negative Pressure Ventilation: Operating Procedure (Iron Lung)," Tufts Medical Center, Respirator Care Programs, http://160.109.101.132/respcare/npv.htm, and http://160.109.101.132/respcare/ironlung.htm, accessed February 27, 2012
18. Szmuk, op cit, page 226-7
19. Fourgeaud, V.J, "Medicine Among the Arabs," (Historical Sketches), Pacific medical and surgical journal, Vol. VII, ed. V.J. Fourgeaud and J.F. Morse, 1864, San Fransisco, Thompson & Company,  pages 193-203  (referenced to page 198-9)
20. "Biographical Dictionary of the society for the diffusion of useful knowledge," Longman, Brown, Green and Longmans, volume III, 1843, A. Spottingwood, London, page 124-5
21. Tissler, Paul Louis Alexandre, "Pneumotherapy: Including Aerotherapy and inhalation...," 1903, Philadelphia, Blakiston's sons and Company, page 284,5
22. Hasan, Ashfaq, "Understanding Mechanical Ventilation: A practical Handbook," 2010, New York, Springer
23. Ball, James B, "Intubation of the Larynx," 1891, London, H.K. Lewis
24. Garrison, Fielding Hudson, "An introduction to the history of medicine," 1922, 3rd edition, Philadelphia and London, W.B. Saunders Company
25. Banser, Robert C., Sairam Parthasarathy, editors, Nocturnal Noninvasive Ventilation, Theory, Evidence, and Clinical Practice," 2015, Springer, New York, chapter 2, "Negative Pressure Noninvasive Ventilation (NPNIV): History, Rational, and Application," by Norma M.T. Braun

1700-1970: Evolution of intubation

How procedure was performed circa 1891 (23, page 20)

Curious physicians started investigating the human body during the course of the 18th century, and they learned a ton about human anatomy. Near the end of the century physicians used this improved wisdom to discover and invent better methods of saving lives, such as intubation and bag mask ventilation.
Such inventions were crude back then, and the methods of performing them must have been traumatic for the patients receiving them, yet they gave physicians something to work with in order to help their patients. The more these physicians struggled, the better they got. The more they tinkered, the better their equipment got.
Here is a pithy progression of some of the results that transpired due to the hard work, and crafty thinking, of a few admirable physicians.

1500:  A paralytic discovered for modern world:   Curare (Succicholine) was one of the most famous native American poison, as the Indians often placed it on the tips of their arrows in order to paralyze their prey. (18, page 4, 177-178) Sir Walter Raleigh first reported the paralytic when he discovered that the South American Tupi Indians used the poison on the tips of their hunting darts. (19, page 1674)

1773:  First resuscitation of near drowning victim:  According to a 1920 publication by the Lungmotor Company, "Drowning: Historical-Statistical Methods of Resuscitation:"

The first reliable history of a resuscitation from drowning was that performed by M. Reamer in Switzerland. This was reported to the French Academy of Sciences and translated into English by Dr. Crogan in 1773. About this time Dr. Fothergill published his "Physical Dissertation on Drowning," which was read before the Royal Society in England. In 1773, the first society for the rescue of those apparently drowned was instituted at Amsterdam, Holland. (20, page 3) (22, page 1)

1774:  Humane Society used bellows to help drowning victims: Members of the society recommended the use of bellows to breathe for victims of accidents (mainly drownings). They recommended that the end of the bellows be placed in one nostril, while the other nostril and mouth were occluded by a second operator. One problem that often occurred was air entering the stomach. Another problem was the tongue blocking the airway. Goodwin ultimately recommended a catheter be inserted into the other nostril into the esophagus to prevent air from getting into the stomach and to keep the tongue from blocking the airway. (22, page 2) (18, page 50-52)

1780:  Bag Mask Ventilation:  In this year a reservoir bag was attached to a mask and used to give breaths to infants who were not breathing at birth. The device was invented by Chaussier. He also invented a cannula (or catheter) that could be inserted into the airway by blind insertion through the mouth into the larynx. His reservoir bag could then be inserted to the cannula to provide positive pressure breaths. (1) He was also the first to provide oxygen breaths to newborns. (2)

1788:  Endotracheal tube:  The first endotracheal tube was invented in 1788 by Charles Kite (Kyte).  He was a surgeon who wrote an essay titled, "The Recovery of the Apparently Dead," in which he described inserting a tube he referred to as a catheter through one of the nares or the mouth to the lungs whereby the operator could either provide positive pressure breaths either by placing his mouth over a mouthpiece or by using bellows.(1)(23, page 50-52)

To cause expiration, Kite recommended pushing in on the abdomen.  Various bellow-type systems were available for providing positive pressure breaths. He also recommended a catheter that was inserted into the esophagus to prevent the tongue from blocking the airway. (1)(23, page 50-52)

On the catheter was an ivory sliding piece that was slid down with a finger into the gullet in order to block the esophagus and prevent air from entering the stomach. Kite's equipment was included in the Case of Resuscitating Instruments that was kept at the various Receiving Houses (Rescue Stations)(1)(23, page 50-52)

1826:  Bellows fall out of favor:  In 1826 by Leroy d'Etiolles performed experiments using bellows and noted in a report that "bellows could kill an animal by suddenly inflating the lungs." (23, page 2) This was among the first reports that showed that over inflating the lungs with too much positive pressure could cause the lungs to collapse.  Due to this report, bellows were no longer recommended by the Humane Society.  (23, page 2)

However, in 1888, "experiments by Leroy were performed that proved that a collapsed lung only occurred when the pressure forced into the lungs was too high, such as greater than 20-80 mm of mercury in the lungs of infants.  As a result of his experiments, he "invented a safety bellows to obviate these effects.  The bellows had a scale graduated in ages attached to the handles to limit the volume of air delivered." (1)  

Experimenters in the succeeding years attempted to create a system of bellows, or methods of fusing them, that were safer to the patient.  

1793:  Intubation to treat diseased patients:  Prior to this time, artificial respiration was generally used to treat near drowning patients or for some other purpose.  Yet near the end of the 18th century artificial respiration was thought to benefit people with diseases or conditions that resulted in dyspnea or asphyxia.  (3, pages 2-4)

This was a time when a tube was sought to be kept inside the airway long-term as opposed to temporary.  Xavier Bichat, a pupil of French surgeon Desault, described how Desault decided to insert a catheter into the larynx of a patient in impending respiratory failure as opposed to a tracheotomy. Desault is considered the first to apply artificial respiration for dyspnea. (3, pages 2-4)

In many cases the patient's breathing became easier, and in one case the patient's breathing became easier and was extubated 24 hours later. Desaults cather "was a large gum-sized elastic catheter, with two large eyes and an opening inferiorly, and he introduced it through one of the nasal fossa rather than the mouth."  (3, pages 2-4)

Catheterization became a common procedure in France, although later fell into disuse.  (3, pages2-4)

1800?:  A paralytic discovered for modern world:   Curare was one of the most famous native American poisons, as the Indians often placed it on the tips of their arrows in order to paralyze their prey. American physicians discovered this poison early on in the 19th century (exact date unknown). Physicians tried to find a safe dose for using it as a paralytic, which was hard to do. They also experimented with various diseases to see if it had beneficial effects. The poison would become an important medicine used by physicians, although it would be a few years before it was proved useful as an anesthetic. (18, page 4, 177-178)

1807:  Method of making Curare discovered:  After Curare was mentioned by Sir Walter Raleigh, many people believed it was made from "poison dart frogs." Alexander von Humboldt discovered that this was not true, that the poison was derived from various vines in the rain forest.  (19, page 1674)

The stems, roots and leaves were crushed and boiled into a paste, which was sometimes mixed with frog and snake venom. A thick black paste was placed on the tips of darts. As they pierced through the skin, the poison would enter the blood stream causing the animal to become paralyzed. (19, page 1674)

Breathing would cease, and the animal was turned into easy prey. This would be a major breakthrough for modern medicine, because it would allow physicians an opportunity to experiment with it on animals, and ultimately on patients of various types. (19, page 1674)

1814:  First use of experiments with muscle relaxants:  Benjamin Brodie (1783-1862) was an English surgeon who performed experiments using Curare (Succicholine) on a donkey, and he proved that so long as the animal was provided with artificial breaths, it could be kept alive during an operation. (2, page 227)(17, page 25)

Charles Waterton gave the Curare while "Brodie supplied the experimental idea." Bellows were used to breathe for the animal for two hours. The animal lived another 25 years. (17, page 25) 

1839:  Intubation fails  Dieffenbach of Berlin tried to catheterize the larynx of a patient inflicted with croup caused by diphtheria and failed. (8)

Figure 1(23, page 6)

1837:  Artificial breathing condemned:  In 1837 Leroy d'Etoille was concerned about the use of such artificial breathing because he suspected it caused emphysema and would collapse the lungs (pneumothorax). (7)
This simply provided another excuse not to perform the procedure, because after the germ theory was established in the late 19th century all methods of performing artificial breaths (positive pressure breathing) was banned for the next 100 years before it's value would be re-established in the later half of the 19th century.  (7)

1845:  Oxygen breaths: A man named Erichson invented the first device that provided positive pressure breaths with oxygen through a cannula inserted through a pipe inserted into one of the nostrils. He recommended ten breaths a minute.

1850:  Jaw-Thrust technique recommended:  One of the problems that must have ensued when a patient was anaesthetised during surgery was asphyxia (or increased risk of it) due to upper airway obstruction. To resolve this problem, anaesthesiologist Joseph Clover (1825-1882) performed the "jaw thrust- chin lift" procedure." (10, page xxi)(9, page 7)

The physician used chloroform as an anesthetic in over 7,000 operations without a single fatality, so other physicians must have been eager to copy his successful techniques.(10, page xxi)(9, page 7)

Due to side effects, and the death of a little girl as a result, the use of chloroform started to wane by 1864, and by WWI was essentially replaced with better, safer anaesthetics (which included both explosive gases and injection through the hypodermic needle that was invented in 1855 by Alexander wood.) (10, page xxi)(9, page 7)

1855: Intubation fails:  Pediatricians become concerned about the large number of children with diphtheria who die despite emergency tracheotomies.  Reybard in Lyon tried to catheterize the larynx of a patient inflicted with croup caused by diphtheria, and failed.  Weinlechner in Vienna tried to catheterize the laryx of a similar patient, and he too failed.  (8)

(26, page 13)

1858:  Bouchut's Intubation Tube is rejected:  In this year French pediatrician Bouchut became the first to describe insertion of a tube into the airway as opposed to a catheter in a case of dyspnea.

The tube he used was a rounded silver tube narrower at the end to be inserted as you can see in Figure 1 It was 1.5 to 2 cm long and 7 cm in diameter. Interestingly, a silk thread was attached to the distal end of the tube that was "brought out to the mouth, and was intended to prevent the tube from going down the trachea or esophagus; and to allow it to be taken out when necessary."

He later "insisted on the distinction between his method and catheterism." However, of the seven cases he cited to the French Academy of medicine, only two lived and both required tracheotomy.

Yet he proved the procedure could be done. Various other physicians described success with this or similar procedures between 1858 and 1880 when the Joseph O'Dwyer introduced his tube (see below) (3, page 5)

Some speculate the reason Bouchut's intubation tube (tubage de la glotte), which "set in the glottic space for a few days" was doomed to be rejected due to a bias created by Dr. Armand Trousseau, who was an ardent supporter of the operation of tracheotomy. Trousseau had previously convinced his fellow physicians that tracheotomy was the best method of creating an airway when suffocation was imminent, even with the low success rate. (12)

The main problem with Bouchut's "small tubes" was that they "did not adapt to the anatomy of the larynx and their sharp edges were a very traumatic cause of lesions to the mucosa and of intense pain." (12) (also see 26,page 13) 

Also of note, since the tube was short, it was barely positioned below the glottis (this would have allowed for air to leak around the tube resulting in diminished lung volumes). (26, page 13)

In the end, "Bouchut and his operation were so bitterly criticised that he became discouraged and abandoned it altogether. So effectually was it crushed out that no further investigations were made in this direction for nearly a quarter of a century." (26, page 13)

Richardson's (21)

1867:  Richardson's Double Acting Rubber Bellows:  Benjamin Ward Richardson created a bellow system similar to Hunter's Bellows (although he may not have known of Hunter's Bellows). The original system took up a lot of room, so he invented the double acting bellows, which "consists of two rubber bulbs terminating in common tube that was called the nostril-tube." One bellow supplied inspiration, the other expiration.

1869: First intubation during operation:  Performed by German physician Friedrich Trendelenburg (1844-1924) to prevent aspiration of blood and mucus during oral operations. 13, page 91)

He is the same person the position "trendelenberg" comes from. This is a position where the patients lies supine (flat on his back) and his feet are set higher than his head.  This is generally done for therapeutic purposes. According to merriam-webster.com, he recommended it in an 1890 paper to provide better access during abdominal surgeries.

Today the position is frequently used in emergency situations when blood pressure is critically low in order to stimulate blood flow to the brain.  It's also often used as one of the various position used to stimulate secretion clearance in diseases that result in thick secretions, such as cystic fibrosis.   

Trendelenburg position

1875:  Blake cures poison victim: Using a device similar to Richardson's Bellows, Blake connected a reservoir of condensed oxygen to it and treated a case of acute poisoning with success. Before this time artificial respiration (often referred to as insufflation) was used mainly to treat neonatal asphyxia, but now the focus was also on treating adults. The nozzle of the device was inserted into the nostril. (1)

1878: The first elective intubation: William Macewan was a Scottish surgeon who, on July 5, 1878, performed the first elective intubation on a patient "with a flexible metal tube" who was not anesthetized. (9, page 7)

"Once the tube was properly positioned, an assistant provided chloroform-air anesthetic via the tube. Once anesthetized, the patient soon stopped coughing." (9, page 7)

The physician lost confidence in his technique when a tube became dislodged and the patient expired. (9, page 7)
His success and failures would become learning points for future surgeons or physicians attempting intubation. (9, page 7)

It also should be noted here that, along with patient anticipation and fear, there was a lot of anxiety among physicians regarding this procedure.  Surely they wanted to help their patients, but they also didn't want to cause further harm by their experimentation.  Macewan, for example, practiced on cadavers prior to intubating any actual living patients.  (9, page 7)

O'Dwyer's Intubation Tube for a child 2-3 years old (23

1880:  The first effective endotracheal tube:  Dr. Joseph O'Dwyer (a pediatrician), and his fellow physicians at the New York Foundling Asylum, observed problems with trachetomy. Once again this occurred during an epidemic of diphtheria where too many children were dying due to suffocation from croup. (3, page 9-18)

Tracheotomy was a viable option as an emergency airway, but it was painful and bloody for children, and the end results were not always positive.  He decided another means of breathing for these children was necessary.   (3, page 9-18)

He at first trialed flexible catheters into the nasal passages, yet this didn't meet his satisfaction.  So he devised a tube to be placed into the larynx where it would remain.  In this way, he picked up where Bouchut left off.  By trial and error he tinkered with the device until it met his satisfaction.   (3, page 9-18)

O'Dwyer's set of five Tubes (26, page 19)

The device was made with a bivalve tube with a narrow transverse diameter, and about an inch long."  A shoulder on the upper end prevented the tube from slipping down (perhaps learned from Macewan's error).  By trial and error the tube transformed so the tube was a "plain tube of elliptical form about an inch in length.  (3, page 9-18)

He then played with longer tubes until he found the desired length.  The final tube used was made of brass and lined with gold, and was accepted by the medical community.  (See figures 2 and 3.)   (3, page 9-18)(also see 26, pages 18-21)

A complete set was included in a box, that included sizes for different aged children, an obturator, an introducer, an extractor, and a gag.   The length of the tubes in inches were 1.5, 1 3/4, 2, 2.25 and 2.5. (3, page 9-18)(also see 26, pages 18-21)

The obturator of the physicians choice is connected to the end of the introducer, and this is used to insert the tube.  If necessary a small thread could be inserted and tied to a hole on the outer edge of the tube to prevent it from going down the traches, and to facilitate removal. (3, page 9-18)(also see 26, pages 18-21)

The kit also came with a scale (see figure  5) which helped the physician determined appropriate depth of the tube according to age.  The scale was used like this:

The smallest tube reaches line 1, and is intended for children about one year and under. The next reaches line 2, and is for children between one and two years. The third size, marked 34 on the scale, should be used between two and four years. The fourth, marked 5-7, is for the next three years, and the largest tube is for children from eight to twelve.

O'Dwyer also designed larger tubes and equipment for adult intubation. (3, page 9-18)

1880:  The Fell-O'dwyer Apparatus:  Once O'dwyer intubated his patient's, he needed a mechanism to breathe for them.  This task fell into the hands of George Fell, who invented a t-piece.  One end of the t-piece was connected to the tracheal tube, and the other to bellows.  The bellows were used to provide positive pressure breaths.  Of course the problem here was it took a lot of manual labor to provide breaths for such patients.  Still, the technique provided physicians an opportunity to help their patients, both when a physician needed to create an emergency airway, and when surgeons needed to perform more invasive operations.  (9, page 7) 

O'Dwyer's introducer connected to obturator (23, page 16)

1887-1888:  George Fell's Apparatus (Hand Operated Bellows): In 1887 Dr. George Fell invented a system of bellows whereby the operator would use his hands to provide positive pressure breaths.  He connected the bellows to either a tracheotomy or face mask. He became the first to perform this procedure on a human in a case of poisoning. (6, page 283)  (22, page 3)

In order to connect the apparatus to the airway, Fell invented a t-piece.  One end of the t-piece was connected to a tracheal tube or mask, and the other to the bellows.  (9, page 7)

Figure 5

1889: The first rubber endotrachal tube:  Thomas Annandale devised a tube made of Indian rubber that was connected from the tracheostomy to (a cap is attached to the trach for just this purpose) to a small tumbler filled with "a piece of absorbent wool at the bottom, upon which chloroform or ether was from time to time sprinkled."  This was significant because a similar material would be used by a later physician to create an endotracheal tube that would be commonly used for over 40 years. (27, pages 261, 838)

1891: The Fell-O'Dwyer Apparatus (Foot operated Bellows):  Once O'dwyer intubated his patient's, he needed a mechanism to breathe for them. George Fell's apparatus must have worked, yet it needed to be fine tuned for ease of use. O'dwyer revised Fell's system so that breaths were provided by pressing down on a lever with his foot. O'Dwyer preferred to connect his bellow system to an endotracheal tube. O'Dwyer was concerned about over-distention of the lungs due not allowing enough time for expiration, and therefore recommended giving slow breaths, or 10-12 per minute. (6, page 283)
1891:  Concerns of Intubation:  By the late 19th century many of the same concerns physicians have today about intubation were considered.  One such concern being the ulceration of tissue due to pressure of the tube set upon it for a long period of time.  Tubes were generally taken out after six days with success, although in some cases were left in 12 days or longer. Dr. Rank, a German physician, ultimately recommended removal of the tube after 10 days, and if necessary, the physician should consider tracheotomy. Some physicians recommended extubation after the 5th day, which would be in line with modern protocols.  Feeding the patient was also a concern, and was either done with soft foods or liquids, or by nasalgastric tube.  It was recommended that if the tube was accidentally spit up that the nurse take advantage of the moment to try feeding the patient prior to re-introducing the tube (if the tube was still needed). (3, page 29-20)

O'Dwyer intubation kit as advertised to physicians in 1901.  (16, page 228)

1892: Dr. O'Dwyer makes pitch for intubation:  In 1892, and according to the New York Academy of Medicine,  Dr. O'Dwyer gave a presentation where he explained that poor statistics shouldn't discourage physicians from performing the procedure, as most studies are performed by "hospital staff, who did not remain on duty long enough to obtain the skill necessary to perform intubation successfully." (14, page 557)

He said:

"The operation of intubation is a difficult one, because it must be done very rapidly.  A period of ten seconds is not safe in some cases, and fifteen seconds would certainly produce apnea in many instances.  The necessary touch and skill require much practice, and this should be acquired on the cadaver until the tube can be inserted in different subjects in about five seconds. It is much easier to perform intubation in some subjects than it is in others.  After such prolonged practice, the operation may be done with comparative safety... No great amount of surgical skill is required to perform tracheotomy, but good nursing is a necessity.  Intubation, therefore, calls for a trained operator, and tracheotomy for a trained nurse."(14, page 557)

Here is another picture of O'Dwyer's Intubation kit. (26, page 27)

He noted that regardless of the challenges, "intubation has supplanted tracheotomy to a very considerable extent, especially in this country (the U.S.)." O'Dwyer further noted that with his new improved equipment, he never found a case in which he found it impossible to insert the tube. (14, page 557)

1892:  Dr. Gay makes pitch for intubation: Another physician, Dr. George S. Gay of Boston, said that...

...intubation is by no means perfect, but it possesses sufficient advantages to give it a permanent place in the treatment of acute laryngeal stenosis (narrowed upper airway caused by croup secondary to diphtheria).  Although it will never entirely displace tracheotomy, the former has some important advantages over the latter.  No anesthetic is required; there is no hemorrhage.  Unless one's early experience with intubation has been particularly favorable, he is likely to prefer tracheotomy.  The strongest advocates of intubation will be found among those who have had the largest experience with it.  The consent of the parents to perform intubation is more easily obtained, and the operation can be resorted to earlier. (14, page 557-558)

This shows the proper position of operator and assistant. 

The assistant holds the head "securely and slightly backward."

The gag should be introduced in the left angle of the mouth,

 well back between the teeth, and widely opened. The operator

 should then quickly seize the introducing instrument with the

 tube attached, hook the loop over the little finger of the left hand,

 and introduce the index finger of the same hand, closely followed

 by the tube" The tube should sit in the larynx. (26, pages 38-40)

1892: Dr. Jacobi makes pitch for intubation: According to the Medical News, Dr. Abraham Jacobi said he performed many tracheotomies (between 600 and 700), but around 1887 he listened to a discussion at the New York Academy of Medicine in which he was "converted from trachheotomy to intubation." (14, page 558)

He warned that, as noted by the Medical News: (14, page 558)

It is very easy to get the parents consent to perform intubation, but it is very difficult to get their consent to perform tracheotomy.  For this reason in many cases the latter operation is performed to late."  (14, page 558)

He said that despite improvements in aseptic techniques, it was still impossible to prevent dying due to sepsis infection of the blood. The Medical News also said that...

...Dr. Jacobi said that, although he is in favor of intubation, and always recommends it, he has never performed the operation personally.  Thirty years ago he was a professed tracheotomist, and on one occasion he was told that he was a good enough man, but that he cut too many throats. (14, page 558)

1893: Cuffed Endotracheal Tube:  It must have also been discovered early on that air was leaking around the tubes, instead of inflating the lungs.  Likewise, some patients must have vomited when the tube was inserted past the gag reflex, and this would have caused aspiration pneumonia, which would spell doom for most patients back then.  Physicians must have sought some means of securing the airway around the tube.  (13, page 91)

According to the 55th anniversary publication of the German Society of Anaesthesiology and Intensive care, Victor Eisenmenger became the first to use an endotracheal tube that had a cuff on the distal end of the tube that was connected by a pilot line to a pilot balloon. Air was inserted with a syringe into the pilot line, and both cuffs would become inflated. The physician would know the distal cuff was inflated when the pilot cuff was inflated. Such a system was soon adapted by other physicians.  (13, page 91)

This is a picture representing insertion of O'Dwyer's tube.
The dotted lines represent the outline of the operator's forefinger.
Back then a finger was used to assist the endotracheal tube to
the desired location in the airway.  The proper tube should be
selected, attached to the introducer, and then introduced to the airwa.
 It was inserted under the tip of the epiglottis, and into the larynx
You  knew the tube entered the larynx when the patient coughs and
the breathing becomes easier.  If it enters the esophagus, breathing
will not become easier.  Once the tube is inside the larynx, the
tube should be disconnected from the introduces.  The tube
should then be pressed forward until it is positioned in the pharynx
Physicians were further warned that "no force should be used,
no anesthetic is required, and the operator should not require
longer than five to ten seconds.
The risk, as you might imagine, was getting bitten by the patient,
and inhaling the same air as the patient, and then getting
the same disease.  Some physicians sacrificed
their lives by attempting to save the lives of their
patients by this procedure.  (26, page 40-42)

1895: First use of laryngoscope:  A laryngoscope was invented to visualize the back of the airway, and was first used by Kirsetein in Germany (15, page 372)

1896: The Fell-O'Dwyer Apparatus modified:  Dr. Northrup recommended the Fell-O'Dwyer apparatus, and it was later modified by Tuller and Hallion of France, and later by Doyan. Doyan's "apparatus consisted of 'duplex' bellows (for insuflation and suction) attached to an intralaryngeal cannula. (22, page 3)

1900:  Cuffed Endotracheal Tubes and laryngoscopes:  Around the turn of the century cuffed endotracheal tubes (ETT) were used with increased frequency.  A larygoscope was first described in 1855 using sunlight to see the vocal cords, and by 1913 a battery powered laryngoscope with an external light was invented.  This was refined so it had a handle with a battery and a light bulb at the end of the scope for easy visualization of the vocal cords.   (2)

1900: Oral intubation becomes popular: Initially the procedure of oral intubation must have been as nerve wracking to the physician as the patient and the patient and the patient's family. However, as with anything, the more it was performed the more confident and competent the physician became in both recommending and performing the procedure. According to a 1911 edition of the New York Medical Journal there must have been enough successes with the intubation by the mouth (per os) by 1900 that it had "found many followers."  (12, page 760)


1900:  Indications for intubation: As more and more physicians became comfortable with laryngeal intubation, they began experimenting with the procedure both on cadavers and on real live patients. The ultimate goal, of course, was to help patients survive diseases that otherwise would have taken their lives. By 1911 some of the indications for the procedure were mentioned in the New York Medical Journal: (12, page 760)

• Narcosis
• Operations (of the mouth, nose, throat and thorax) (12, page 760)

1900-1912:  Intubation technique improved: Frank Kuhn, a German physician, published a series of papers where he "described the techniques of oral and nasal intubation that he performed with flexible metal tubes composed of coiled tubing similar to those now used for the spout of metal gasoline cans." (11, page 7)

The tubes were of his own design. (13, page 91)

As a local anaesthetic to prevent the gag reflex he used cocaine.  He introduced the tube into the airway with a metal stylet.  He used the index finger of his left hand to lift the tongue and the glottic tissue, and used his right hand to insert the tube through the vocal cords.  While cuffs were used by other physicians to seal the airway.  He preferred to have it sealed by "positioning a supralaryngeal flange near the tube's tip before packing the pharynx with gauze."  (11, page 7)  (13, page 91)(also see 22, page 3) 

To see a very good picture of Kuhn's procedure check out this link.  

1902: O'Dwyer apparatus modified again:  This modification was made by R. Matas who 'Constructed an apparatus in which a modified O'Dwyer tube was connected with an automatically acting pump.  The pump contained originally two independent metal cylinders for inspiration and aspiration.  However, the first experiment made on a dog convinced Matas that the suction force, exercised by the aspiration cylinder, does damage to the lungs, and he eliminated that part of the apparatus. (22, page 3)

1913:  Modern laryngoscope invented:  A better laryngoscope was invented by Jackson, and it was later improved by Miller and Mackintosh (see below) (14, page 372)

1914-1918: Magil invents blind intubation:  During WWI Dr. Magill performed a variety of facial reconstruction surgeries. He discovered that in order to do such surgeries the patient had to be intubated.  Along with Stanley Rowbotham, he developed a method of tracheal intubation.  He blindly inserted one tube of gum elastic design into one nostril.  In this way he coined the term "blind intubation."  (24, pages 8, 753)

There were two problems with this system.  One was that anesthetic gas was escaping the tube, and the operating physician was inhaling this gas. Obviously, this affected his work.   The other was that blood and other debris from the operation would fall into the airway when the tube was pulled.  Obviously, this was detrimental to the patient.  So a two-tube system was developed.  One tube was blindly inserted into a nostril to the larynx to breathe and to apply the anesthetic, and the other through the mouth into the pharynx to provide for the escape of gases.     (24, pages 8, 753)

He became so proficient at his method that students from all over came to watch and learn his method. While he taught his method, other physicians continued to have trouble inserting the tubes due to patient agitation, while Magill did not. Magill had a secret that he refused to tell the students: that he applied cocaine as a local anesthetic to the throat. (25, page 110)
The rubber endotracheal tubes used by Magill were standard for the next 40 years until being replaced with plastic tubes. (24, page 8)

1920: Magill Forceps introduced:   In order to guide the nasal tube into the airway, Magill used forceps that still bear his name (Magill Forceps) (15, page 372)(24, page 8)

1926: Guedel experiments with cuffed endotracheal tubes:  Noting the need to protect the lower airway from secretions and surgical debris, Arthur Guedel (1883-1956) performed experiments with using a cuffed endotracheal tube.  His cuff was made out of rubber. His experiments also determined that the best place to position and inflate the cuff was just below the vocal cords.  This, he found, was the best way of protecting the airway during intubation.  Once this task was accomplished, he aimed to encourage stubborn American physicians of the benefits of intubation.  (24, page 8)

1926: Guedel inspires American physicians to intubate:  While European physicians intubated on a regular basis during operations, American surgeons used other means.  Noting the benefits of intubation, Arthur Guedel put on a show where he went around the country with his dog named Airway.  He would anesthetize and intubate his dog, and then submerge it under water.  Just as the audience suspected the dog was dead, he would pull it from the water, extubate it, and the dog would shake off the water and run off.  These shows became known as the Dunking Dog Shows, and proved that intubation not only allowed the physician to breathe for the dog, but the inflated cuff prevented water from getting into the dog's lungs.  These efforts worked, as American physicians soon became proficient in the procedure of intubation. (25, page 111)

1930:  Oral Airway Introduced:  Ralph Waters (1883-1979) introduced the flattened oral airway, and it was later modified by Guedel by fitting the oral airway with a "rubber envelope in an attempt to reduce mucosal trauma." (24, page 753)

1932:  One lung intubation introduced:  Ralph Waters accidentally allowed an endotracheal tube to slip all the way into a patient's lungs, and he inflated the cuff. In this way he learned that one lung could be intubated with a long endotracheal tube while the other was operated on. This made it possible to do lung operations. (24, page 8)(25, page 111)

1942:  Anesthesia during intubation: By the 1880s intubation was being increasingly used for children with airway stenosis secondary to croup secondary to diphtheria.  As a physician observed that the patient was going to suffocate to death unless he did something, the choice was offered to the parents: intubation or tracheotomy?  (2, page 227) (19, page 1674)

Intubation must have presented as the best option in many cases, as the procedure would avoid a cut of the throat.  A problem that continued was the procedure caused quite a bit of anxiety on the part of the patient, as you might imagine.  If the child fought the efforts of the physician, this could make the procedure very difficult to perform. (2, page 227) (19, page 1674)

Cocaine was occasionally used as a local anesthetic to prevent the gag reflex, and general anesthetics were occasionally used to paralyze the patient, although these were only used if the physician was familiar with them and comfortable with their use.  (2, page 227) (19, page 1674)

In 1942, Harold Griffith, A Canadian anesthesiologist, made a major breakthrough in this regard on January 23, 1942, when he and his assistant, Dr. Enid Johnson (also an anesthesiologist) used Curare to paralyze a patient prior to intubation. He used it as an anesthetic in 23 operations, and wrote a report on his successes with it. (2, page 227) (19, page 1674)

This was a major breakthrough because it allowed the surgeons to sedate and ventilate patients during the operation.  (2, page 227) (19, page 1674)

WWII:  Intubations proficiency increases worldwide:  In preparation for the traumas generally associated with battle wounds, anesthesiologists practiced and became very proficient at performing the procedure of intubation.  The methods learned became standard practice, and over time intubation training became a regular part of a physician's training.  (25, page 753)

1964: Plastic endotracheal tubes introduced: They were actually made of polyvinylchloride (PVC) with an inflatable cuff. Rubber tubes tend to harden when exposed to body temperature.  PVC tends to soften at body temperature, and is therefore less likely tocause damage to tissues of the airway.  The tubes are also clear and opaque.  They come with markers so caregivers know how far down the tube is inserted.

1970:  High volume, low pressure cuffs introduced:  Previously, cuffs were low volume high pressure.  When inflated, these cuffs came into contact with very little area of the trachea, and created a great seal.  However, due to the high pressure, risk of cutting off circulation and causing necrosis was high.  High volume, low pressure cuffs would come into contact with more tracheal tissue, although the lower pressure was less traumatic.  Surely the cuff pressure would have to be minimized, and the cuff may need to be rotated up or down 1-2 cm on a regular basis to minimize tissue damage, yet this was a much better set up than the older cuffs. The drawback is the seal is not ideal.

Conclusion:  So you can see that physicians were slow to begin using intubation, although experiments by the few, in an attempt to help their patients, resulted in both an improvement in the technique used and the equipment available.  By the 1940s intubation during surgery became standard practice, and by the 1950s it became standard across the medical spectrum, including on the scene of an accident and emergency rooms.

While fireside bellows remained the preferred method of providing breaths through the endotracheal tube, the quest was ongoing to find a mechanical device that would provide breaths in a fashion that was less laborious for the provider, and safer for the patient.

References:

1. Price, J.L., "The Evolution of Breathing Machines," Medical History, 1962, January, 6(1), pages 67-72; Price references The Bible, Kings, 4: 34 
2. Szmuk, Peter, eet al, "A brief history of tracheostomy and tracheal intubation, from the Bronze Age to the Space Age," Intensive Care Medicine, 2008, 34, pages 222-228
3. Ball, James B, "Intubation of the Larynx," 1891, London, H.K. Lewis
4. Woollam, C.H.M., "The development of apparatus for intermittent positive pressure respiration," Anaesthesia, 1976, volume 31, pages 537-147
5. Previtera, Joseph, "Negative Pressure Ventilation: Operating Procedure (Iron Lung)," Tufts Medical Center, Respirator Care Programs, http://160.109.101.132/respcare/npv.htm, and http://160.109.101.132/respcare/ironlung.htm, accessed February 27, 2012
6. Tissler, Paul Louis Alexandre, "Pneumotherapy: Including Aerotherapy and inhalation...," 1903, Philadelphia, Blakiston's sons and Company, page 284,5
7. Lee, W.L., A.S. Stutsky, "Ventilator-induced lung injury and recommendations for mechanical ventilation of patients with ARDS," Semin. Respit. Critical Care Medicine, 2001, June, 22, 3, pages 269-280
8. Sperati, G., Felisati, D., "Bouchut, O'Dwyer and laryngeal intubation in patients with croup," Acta Otorhinolaryngol Ital, 2007, 27 (6), 320-323
9. Barash, Paul G, Bruce F. Cullen, Robert K. Stoelting, Michael Cahalan, M. Christine Stock, editors, "Clinical Anesthesia," 6th edition, 2009, China, Lippincot Williams and Wilkins
10. Subramaniam, Rajeshwari, "A primer of anesthesia," 2008, MO, Jaypee Brothers Medical Publishers
11. Barash, Paul G., Bruce F. Cullen, robert K. Stoelting, Michael k. Cahalan, M. Christine Stock, "Clinical Anaesthesia," 6th edition, 2009, Philadelphia, Lippincott
12. Foster, Frank P., editor, "Book Notices," New York Medical Journal, volume 94, New York, A.R. Elliott Publishing Co.
13. Schuttler, Jürgen, editor, "55 years: German Society of Anaesthesiology and Intensive Care Medicine," 2012, Germany, Springer
14. Gould, George M., editor, "Society Proceedings: New York Academy of Medicine: Stated Meeting, Thursday Evening, October 20, 1892," The Medical News, A Weekly Medical Journal," July-December, 1892, Vlolume LXI, Philadelphia, Lea Brothers and Co., pages 557-558
15. Hagberg, Carin A., "Benumof's Airway Management," 2007, Philadelphia, Mosby
16. "Blees-Moore Instrument Company: surgical instraments," 1901, St. Louis, MO, Burton and Skinner Print
17. Miller, Ronald D., editor, "Miller's Anesthesia," 7th edition, volume 1, 2010, Philadelphia, Churchill Livingstone Elsevier
18. Vogel, Virgil J., "American Indian Medicine," 1970, London, Oklahoma University Press
19. Wheeler, Derek S., Hector R. Wong, Thomas P. Shanley, editors, "Pediatric Critical Care Medicine: Basic Science and Clinical Evidence," 2007, London, Springer
20. "Drowning: Historical-Statistical Methods of Resuscitation," no author nor editor listed, Published by Lungmotor Company, Boston, Massachusetts, 1920
21. Hughes, Martin, Roland Black, "Advanced Respiratory Critical Care,"  2011, New York, Oxford University Press; material from section 3.1: "Invasive Ventilation Basics: Development of Invasive Ventilation (history)."
22. Meltzer, S. J., "History and analysis of the methods of resuscitation," Medical Record: A Weekly Journal of Medicine and Surgery, July 7, 1917, Volume 92, Number 1, New York, 
23. The Forty Ninth Annual Report of the Royal Humane Society, For the Recovery of  Persons Apparently Drowned or Dead," 1823, London, 
24. Barash, Paul G. Bruce F. Cullen, Rober, "Clinical Anesthesia," 2009, Philadelphia, Lippincott
25. Friedman, Meyer, Gerald W. Friedman, "Medicine's 10 Greatest Discoveries," 1998, Yale University
26. Waxham, F.E., "Intubation of the Larynx," 1888, Chicago, published by Charles Traux (Waxham was an early proponent of intubation for diptheria and croup. 
27. Gould, George M, "American Year-book of Medicine and Surgery," 1899, Philadelphia, W.B. Saunders
28. Curry, James, "Observations on Apparent Death from drowning, hanging, suffocation by noxious vapours, fainting-fits, intoxication, lightning, exposure to cold, & etc., and an account of the means to be employed for recovery. To which are added the treatment proper in cases of poison, with caution and suggestions respecting various circumstances of sudden danger," 2nd edition, 1815, London (the 1st edition was published in 1792)

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