|Figure 4 (21)|
It should be noted here that anytime positive pressure breaths are given to patients there is always the risk of applying too much pressure and blowing out a lung, thus causing a collapsed lung, more technically referred to as a pneumothorax. This is often referred to as barotrauma.
This was a major concern for the makers of ventilators all the way to the current century. Safety measures on modern ventilators work to prevent barotrauma. Yet back when these devices weren't so common, coming up with safety measures must have been a major concern. Much experimentation had to take place before any apparatus was put into use on any patient.
R. Matas devised 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. (6, page 284)
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. (6, page 284)
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. (6, page 284)
- Tissler, Paul Louis Alexandre, "Pneumotherapy: Including Aerotherapy and inhalation...," 1903, Philadelphia, Blakiston's sons and Company, page 284,5