You and a friend are having a contest to see who can hold his or her breath the longest. Your friend hyperventilates before holding his breath, and subsequently wins the contest. Why did hyperventilation give him an advantage?

Video transcript

Welcome back, everybody. Let's take a look at our next question. Hyperventilating before taking a deep dive into a pool would allow a diver to hold their breath longer. What changes allow this to happen? A the initial drop in CO2 would allow the diver to accumulate more CO2 while holding their breath. B the increase in oxygen will inhibit the respiratory center. C. The increase in oxygen would cause the blood ph to decrease or D all of the above. Well, the first thing we can note is choice C is obviously incorrect. The increase in oxygen would cause the blood ph to decrease is an increase in the concentration of CO2 that causes the blood to become more acidic. So whether regardless of whether or not that's what's happening with hyperventilation, that's just an incorrect description of what happens in the body. So choice C is incorrect. So choice D all of the above can also be ruled out. So now we just need to look at is it the initial drop in CO2 or the increase in oxygen? Well, one thing to note here, the crucial thing is that the chemo receptors that sense the concentration of carbon dioxide in the blood are much more sensitive than those that sense the concentration of oxygen. So a change in the concentration of carbon dioxide in the blood will be much more, have much more effect on triggering the respiratory muscles than a change in the concentration of oxygen. And this is ok because most of the time these two are paired together in terms of why hyperventilating would allow you to hold your breath longer. Our answer is choice. A in hyperventilation, you have this rapid breathing that expels large amounts of carbon dioxide. So the concentration of carbon dioxide in the blood will drop very low. Then while the divers holding their breath, their carbon dioxide concentration is going to be rising, the longer they hold their breath. But they started from this low point. So they can tolerate a lot longer before those chemo receptors are triggered and stimulate the respiratory muscles. So the very low initial drop in carbon dioxide, as choice A says will result in a longer time before the concentration of carbon dioxide rises enough to stimulate the chemo receptors. So the diver can accumulate more carbon dioxide while holding their breath. When we look at choice B, the increase in oxygen will inhibit the respiratory center. Well, again, the oxygen levels are not going to impact this nearly as much. Those chemo receptors are not as sensitive. So, Choice B is not going to be the effect. And in fact, it's a danger with hyperventilation that the person can pass out from lack of oxygen before they even get to the point where they need to take a breath from accumulation of carbon dioxide. So again, that carbon dioxide concentration is more significant in terms of the chemo receptors than the level of oxygen. So why hyperventilating allows a diver to hold their breath longer? Our answer is choice. A the initial drop in carbon dioxide allows the diver to accumulate more carbon dioxide while holding their breath. See you in the next video.