Tuesday, 7 October 2008

How does asthma cause a pneumothorax?

Firstly, we should remind ourselves that asthma very seldom causes a pneumothorax. Nonetheless, it is a (rare) recognised complication. How does it happen?

Asthma is an obstructive lung disease. By this I mean that the primary abnormality is that less air can be breathed out than normal. Therefore at the end of a full expiration, there is a greater 'residual volume' of air in the lungs than usual.

Compounding the problem of increased amounts of 'useless' air stuck in the lungs, asthmatic patients will tend to forcefully exhale as well as cough excessively, the latter in particular dramatically increasing the force exerted on the lungs.

Normally this force quickly forces most of the air out of the lungs, but in an asthmatic, the air can't escape as easily or as fully as before. The increased force may therefore cause part of the lung to 'burst' and communicate with the pleural space. This causes a pneumothorax.

It's a little like squeezing the air our of a balloon. If you allow the air to escape normally, the balloon simply deflates. However, if you gradually close off the balloon's outlet, you increase the odds of it bursting.

3 comments:

  1. I remember when I brought my son in the hospital because of asthma and they gave him medicines.

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  2. Thanks for sharing this extremely informative article on what is asthma and causes. I recently read about asthma attack on website called breathefree.com. I found it extremely helpful.

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