Question High Altitude Athletes.... Less efficient at depth?

[tarponchik]

Totally false.

He is right. We have sensors for high CO2 level but no sensors for low O2.

 

[Sure Squintsalot]

As others have said, there are many other factors that determine your air consumption.

As an anecdote, one of my diving buddies is a Mt. Everest climbing guide. He is shorter than me and weighs less than me, but our air consumption is the same. Our wives consume 40% less air than we do, so we always get the bigger tanks on holidays.

Previous posters are arguing that the high PO2 (of breathing air at depth) eliminates any physiological O2 processing advantage of aerobic fitness; in other words, smokers and Everest guides should , all else being equal, consume air at the same rate. It's hard to agree with this statement.

Others have correctly pointed out the role CO2 plays in respiratory drive. I've just read that the pressure of arterial CO2 increases with depth. Maybe that's the question to ask: Do high altitude athletes respond to PCO2 more efficiently? And does that mean more breathing and less time underwater?

 

[boulderjohn]

The Process of Breathing | Anatomy and Physiology II

courses.lumenlearning.com

From the article:

The major factor that stimulates the medulla oblongata and pons to produce respiration is surprisingly not oxygen concentration, but rather the concentration of carbon dioxide in the blood. As you recall, carbon dioxide is a waste product of cellular respiration and can be toxic. Concentrations of chemicals are sensed by chemoreceptors. A central chemoreceptor is one of the specialized receptors that are located in the brain and brainstem, whereas a peripheral chemoreceptor is one of the specialized receptors located in the carotid arteries and aortic arch. Concentration changes in certain substances, such as carbon dioxide or hydrogen ions, stimulate these receptors, which in turn signal the respiration centers of the brain. In the case of carbon dioxide, as the concentration of CO2 in the blood increases, it readily diffuses across the blood-brain barrier, where it collects in the extracellular fluid. As will be explained in more detail later, increased carbon dioxide levels lead to increased levels of hydrogen ions, decreasing pH. The increase in hydrogen ions in the brain triggers the central chemoreceptors to stimulate the respiratory centers to initiate contraction of the diaphragm and intercostal muscles. As a result, the rate and depth of respiration increase, allowing more carbon dioxide to be expelled, which brings more air into and out of the lungs promoting a reduction in the blood levels of carbon dioxide, and therefore hydrogen ions, in the blood. In contrast, low levels of carbon dioxide in the blood cause low levels of hydrogen ions in the brain, leading to a decrease in the rate and depth of pulmonary ventilation, producing shallow, slow breathing.​

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Blood levels of oxygen are also important in influencing respiratory rate. The peripheral chemoreceptors are responsible for sensing large changes in blood oxygen levels. If blood oxygen levels become quite low—about 60 mm Hg or less—then peripheral chemoreceptors stimulate an increase in respiratory activity. The chemoreceptors are only able to sense dissolved oxygen molecules, not the oxygen that is bound to hemoglobin. As you recall, the majority of oxygen is bound by hemoglobin; when dissolved levels of oxygen drop, hemoglobin releases oxygen. Therefore, a large drop in oxygen levels is required to stimulate the chemoreceptors of the aortic arch and carotid arteries.​

 

[grantmac]

Normally, it isn't a problem, but this guy is able to constantly inhale and exhale at the same time. It's like a slow freeflow...

Exhaling through your nose is not a problem, unless you do it at such a taste that you are constantly flooding your mask... Again, probably not a problem unless you're just learning to dive.

Does this person have a minor/repaired cleft palate? Because a good friend of mine has one and she can't avoid breathing through her nose a little. Makes diving very challenging and I've been trying to get her to try a FFM.

 

[Vicko]

Really? So we can breathe pure nitrogen or helium?

Your brain thinks it can, and will hapilly let you do it untill you pass out.

 

[VikingDives]

Your brain thinks it can, and will hapilly let you do it untill you pass out.

Your reply to me wasn't my comment...

 

[VikingDives]

Does this person have a minor/repaired cleft palate? Because a good friend of mine has one and she can't avoid breathing through her nose a little. Makes diving very challenging and I've been trying to get her to try a FFM.

No, he can breathe out of his mouth if he concentrates.

 

[DirtFish]

My wife was a nose breather when she was first learning scuba. I had her swim around in the lake everyday for a month with just a snorkel, no mask and that worked for her. Cured!

 

[Doc Harry]

We have sensors for high CO2 level but no sensors for low O2.

Totally false

 

[Doc Harry]

....If blood oxygen levels become quite low—about 60 mm Hg or less—then peripheral chemoreceptors stimulate an increase in respiratory activity. The chemoreceptors are only able to sense dissolved oxygen molecules, not the oxygen that is bound to hemoglobin. As you recall, the majority of oxygen is bound by hemoglobin; when dissolved levels of oxygen drop, hemoglobin releases oxygen. Therefore, a large drop in oxygen levels is required to stimulate the chemoreceptors of the aortic arch and carotid arteries.

I've performed emergency intubations of quite a large number of people - literally thousands - who were hyperventilating and plunging into respiratory failure due to hypoxemia (low O2) not hypercapnea (high CO2). Blood gasses showed a reduced pCO2 from hyperventilation, and a pO2 that has NEVER been even close to 60mm. At 60mm most people are unconscious and dark blue. We don't let them get that far. It doesn't take much hypoxemia (low O2) for people to start getting very anxious and start struggling to breathe, and they'll tell you "I CAN'T BREATHE!" If other measures don't help they get too exhausted to breathe and often that's when they get intubated.

I've also performed emergency intubations of thousands of people with hypercapneic (high CO2) respiratory failure. Different problem, different clinical picture.