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Will I hyperventilate if I breath twice as fast at an altitude with half as much oxygen as I am used to? If not twice as fast, should I breath any amount faster on average than usual when at high altitudes?

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  • $\begingroup$ Possibly better suited to Health S.E. $\endgroup$
    – L.B.
    Dec 4, 2016 at 19:59
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    $\begingroup$ Maybe I gave of the wrong impression in my question. This is purely theoretical, and I don't care about the health effects of hyperventilation. I'm interested in the biological basis for hyperventilation and whether hyperventilation occurs due to increased respiration alone, or some combination or respiration and oxygen levels. $\endgroup$
    – nullUser
    Dec 4, 2016 at 20:26
  • $\begingroup$ Understood. But I think it would have worked on that site as well. I don't believe it will be closed or anything here though. :) $\endgroup$
    – L.B.
    Dec 4, 2016 at 20:37
  • $\begingroup$ you also breath 2x as much other gases when breathing faster $\endgroup$ Dec 4, 2016 at 20:58
  • $\begingroup$ probably this article (ncbi.nlm.nih.gov/pmc/articles/PMC3495772) will answer some of your questions $\endgroup$
    – KingBoomie
    Dec 4, 2016 at 22:00

1 Answer 1

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By definition, hyperventilation is a state of increased breathing where the exhaled $CO_2$ is greater than what is produced by the body.

Except in artificial condition or in disease process, breathing faster than the autonomously-dictated rate is going to cause hyperventilation. You have a fine-tuned control of respiration that will work out the correct breating rate for you.

Oxygen is actually irrelevant for this phenomenon, first because of the definition of hyperventilation, but also because oxygen is mostly transported through haemoglobin (98+%). This means there is a fixed quantity of oxygen that can be transported by unit volume of blood (and by breath, for a given cardiac output), and the maximum is already reached at normal breathing rate. Breathing faster does not allow for better oxygenation of the blood. (even at an higher altitude)

On the other hand, $CO_2$ is transported by the plasma, dissolved (7%), but also in the form of bicarbonate (93%) through the following equilibrium :

$$ H_2O + CO_2 \rightleftharpoons \underbrace{H_2CO_3}_\text{Carbonic acid} \rightleftharpoons \underbrace{HCO_3^-}_\text{Bicarbonate} + H^+ $$

In the alveoli, a quantity of $CO_2$ will diffuse to the alveolar air, and be breathed out, the target being eliminating the quantity produced by the body. However, in opposition to oxygen transport, it is possible to overshoot by breathing faster, because removing $CO_2$ drives the equilibrium in direction of $H_2O + CO_2 \leftarrow HCO_3^- + H^+ $ that is, eliminating additional $CO_2$ through the removal of bicarbonate from the blood.

This is hyperventilation, and leads to hypocapnia, causing that particular sensation of dizzyness. It is also leads to respiratory alkalosis, because, as seen in the reaction equation, this incurs the loss of protons ($H^+$).

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