Wednesday, July 6, 2016

1819: Laennec is first to describe lung sounds

After he invented the stethoscope in 1819, it was then next task of him to perform experiments with it.  As he was the first to auscultate with this device, he would also be the first to describe lung sounds.

He noted first normal lung sounds, although he did not refer to them as clear as we do today.  He also noted an array of adventitious noises in the lungs among those who were not healthy, and for this he needed a name.  He said:
For want of a better or more generic term I use the word rhonchus* to express all the sounds, besides those of health, which the act of respiration gives rise to, from the passage of the air through fluids in the bronchi or lungs, or by its transmission through any of the air passages partially contracted. (1, page 55)
M. Andrus said Laennec chose the term rhonchus because...
...It was desirable that some name might be found for this phenomenon which would prove generally acceptable to British physicians.  In the former edition of this translation, the nearest English synonym, rattle, was used, but this word has been adapted by few.  The original French term rale appears to be most generally employed in this country, but there are several objections to its use. (1, page 55)
Today, the term rhonchi is used to describe the sound of air moving through secretions, and the term wheeze is used to describe the sound of air moving through air passages partially contracted.  Rhonchi is generally heard as a coarse sound, is continuous, and is often times confused as a wheeze.

Laennec avoided this confusion simply by calling all continuous sounds rhonchi. Today, many medical caregivers avoid the confusion by calling all continuous lung sounds a wheeze.  So there really is not much difference here other than the term used.

While we generally describe the various lung sounds as clear, diminished, rhonchi, wheeze and crackles, Laennec basically described five types of rhonchi, as follows (modern term I think he is referring to is in parenthesis): (1, pages 55-62)
  1. Moist crepitous rhonchus, or crepitation:, similar to the sound of blowing into a dried bladder, or the sound made by rubbing between the finger and thumb a piece of hair, or the noise of boiling butter.  This is a sign of the early stage of peripneumony and edema of the lungs and pulmonary apoplexy (crackles)
  2. Mucous rhonchus, or guggling: Formed by the passages of air through sputa in the bronchi, and sounds like bubbles, or blowing through a pipe into soapy waters. The sound of the bubbles can be described as middling, small, large, or very large, and is a sign of peripneumony or suffocative catarrh in old people near death (the death rattle) or those dying of phthisis, or hemoptysis, or phthisis, or diseases of the heart, or tuberculosis excavations, and may be regarded as an evil omen (tracheal Rhonchi, large airways, or upper airway rhonchi, and may be audible, as in a death rattle)
  3. Dry sonorous rhonchus, or snoring: Crackling rhonchus; Flat grave sound, sometimes extremely loud, sounding like a person snoring, and may be diagnostic of pulmonary fistula, or dilated bronchi, and may be caused by temporary inflammation or contraction of the bronchi (rhonchi or sonorous wheeze, )
  4. Dry sibilous rhonchus, or whistling: Prolonged whistle flat or sharp, dull or loud, and may sound like the chirping of birds, and may be caused by thick secretions obstructing the airway or local contraction of the smaller bronchi (wheeze)
  5. Dry crepitous rhonchus, with large bubles or crackling: The sound of air entering lungs that had been dried, or air cells or vesicles (alveoli) that had been unevenly dilated, may make noise similar to that produced when blowing into a dried bladder.  May be indicative of emphysema  (fine inspiratory crackles heard upon the opening of previously collapsed alveoli) (1, pages 55-62, 98)
Andral said he would differentiate the rhonchi based on whether the cause was in the air cells (alveoli), the air passages (bronchi) or some morbid excavations formed in the substance of the lungs (secretions). He would break the sounds down this way: (2, page 55)
  • Vesicular Rhonchi: Originating from the vesicles or air cells (alveoli)
  • Bronchial Rhonchi: Originating from the bronchial tubves
  • Cavernous rhonchi: Originating from morbid excavations
He further noted that lung sounds are either humid or dry.  (2, page 55)

He would then break them down this way: (2, pages 55-56)
  1. Humid vesicular rhonchus: Moist crepitous rhonchus, Rale crepitant of Laennec (coarse crackles or rhales)
  2. Dry vesicular rhonchus: Dry crepitous rhonchus, rale crepitant  (fine inspiratory crackles)
  3. Humid bronchial rhonchus: Mucous rhonchus (Rhonchi)
  4. Dry bronchial rhonchus: Sibilous rhonchi, rale sibilant (wheeze)
  5. Humid cavernous rhonchus: May be caused by abscess or gangrene of the lungs or the later stages of tubercle or phthisis, and may sound like mucous rhonchus or guggling, and is usually over a small spot (as in just over the area affected, and is usually heard with deep inspiration or while coughing)
  6. Dry cavernous rhonchus: described because it is possible, not that it has ever been described by any author (2, page 55-56)
Andral said that little was added to the description of rhonchus between the time of the first edition of his book in 1819 and the 4th edition in 1838.  He noted that a flaw in Laennec's description of the various lung sounds was that he did not mention at what point during the respiratory phase the sounds were heard. (2, page 62)

Andral said this was an important thing left out, because some sounds are heard only on inspiration, or only on expiration, and sometimes both.  So he added the following:
  • Crepitous rhonchi or vesicular rhonchi: heard only on inspiration because it is a noise produced by the air vesicles cracking open
  • Humid Bronchial rhoncus: heard during inspiration and expiration, and mostly during expiration because it is the sound of air moving through secretions, and the secretions are there at all stages of respiration
  • Sibilous and sonorous rhonchi, or dry bronchial rhonchus: Heard oftener during expiration more so than inspiration
  • Mucous rhonchus: Heard during both inspiration or expiration
So you can see that little has changed regarding the description of lung sounds other than the terms used.  The terms often varied from one author to the next, and this is true even to this day.

  1. Laennec, Rene, "Mediate Auscultation," translated by John Forbes, Notes by professor Andral, 4th edition, 1838, New York, Samuel S. and William Wood
  2. Andras, author of the notes in the book, "Mediate Auscultation, by Rene Laennec," ibid 
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