Expert: Neal Okerson - 4/13/2005

Question
Our biology teacher informed us that after a person "exhales" air that a portion of air remains in your lungs as "residual" air.
A student asked if someone drowned would the lungs contain any residual air anymore? Or would all the air be pushed out and filled up with the incoming water?
Told the class I would write you to find an answer.
Thanks!!!!!!!!!!

Answer
Jim,
Sorry for the slow response - I've been out of town.

Your biology teacher is correct. When you exhale, part of the air stays in your lungs.

The lungs/airways are often called a bronchial tree. This is because of the similarity to the shape of a tree. The trunk and progressively smaller limbs are the airways while the leaves are like the alveoli where most of the gas exchange takes place. Now if someone drowns, the water will replace most of the air in the larger airways. The water gets down into many of the smaller airways and even into the alveoli in some places. The residual air that does remain will become useless because it cannot be exchanged with fresh air.

Good question!
Neal