Tag: physiology

“Respiratory embarrassment” is an uncommon phrase most likely spoken by physicians and physiologists.

This week I found myself telling an engineer that “respiratory embarrassment can lead to an untoward event”. It quickly became apparent from the puzzled stare I received that I was not communicating.

Scientists and some medical personnel tend to do that; fail to communicate. In fact, they do it a lot.

What I was really saying is that in the right circumstances a person could have difficulty breathing, and that difficulty could cause something bad to happen; an “untoward” event. That bad thing would not necessarily be an aircraft crash, or in the case of a diver, a drowning, but it would mean that the pilot’s or diver’s performance would be impaired.

Why didn’t I just say so?

Laziness I suppose. I was using the language clinicians and physiologists are taught in graduate or medical school, and it flows out of our mouths naturally, without effort. Translating those same words into laymen’s terms takes time and effort.

I next started talking about respiratory impedance, a term understood by some but not all engineers, and rarely if ever by laymen. So once again I was not communicating well with all of my audience which was composed mostly of engineers, but not entirely.

That was the case until I used pictures to explain the otherwise difficult concepts of respiratory impedance and physiological embarrassment. The images below seemed to work, so I thought it worthwhile to share those images with you.

For you engineers, respiratory impedance is proportional to the sum of respiratory flow resistance and pulmonary and chest wall elastance.

So what is that?

Well, for elastance, at least chest wall elastance, think of being buried to your neck in sand. Breathing difficulty comes from the difficulty of moving your chest wall in and out with the weight of sand pressing in on all sides. The pressure of sand impedes your breathing, hence elasticity (the inverse of compliance) is a major component of respiratory impedance.

Based on the photo of the young man pictured on the right, being partly buried for supposedly therapeutic reasons is not a pleasant experience.

Some might disagree. The man on the left is an actor in the 2008 French short film Le Tonneau des Danaïdes by David Guiraud, who seems quite at ease impeding his breathing for the sake of art. I’m guessing he’s either very dedicated, or very well paid.

In diving, respiratory elastance can be elevated by tight fitting wet suits; in aviators by tight fitting chest pressure garments, and in patients, by pulmonary fibrosis brought about by, for example, asbestos exposure.

Another key component of respiratory impedance, that thing that causes respiratory embarrassment, is flow resistance. Sticking your head in the sand would certainly be one way of generating

severe respiratory resistance, with its attendant embarrassment.

Clinically, there are far more common sources of respiratory resistance, for example the narrowing of air passages in the lung caused by asthma. (Sticking your head in sand is probably a reasonable analogy to the sensations experienced during an asthma attack.) Chronic obstructive pulmonary disease (COPD) can also lead to a significant increase in respiratory resistance.

When you focus on the human respiratory system, the body parts shown in pink below, keep in mind that breathing can be impaired by things occurring inside the body (like asthma, COPD, fibrosis) or outside the body. Any life support system used for aviation, diving, mining, or firefighting imposes an impedance on breathing. That impedance in turn can lead to breathing difficulty, which can result in a failure to complete assigned duties.

Perhaps that’s where the “embarrassment” part comes in.