Actually, hypoxia really just describes a reduced amount of oxygen entering the bloodstream. Most often, this is caused by an increase in altitude, but that is not the only situation that can cause hypoxia.
Temperature, for example, does have an effect on the oxygen-hemoglobin dissociation curve. See
this graph. According to the graph in the upper-left, under the same partial pressure of oxygen, the % saturation of hemoglobin with O2 will actually decrease as temperature increases. So
theoretically, then, a person could suffer from hypoxia while standing outside at sea level if the temperature were hot enough. In reality, there probably isn't any place on the surface of the planet that gets hot enough for that to happen.
However, again in theory, one could see how a higher temperature could exacerbate the effects of high altitude (reduced partial pressure of O2), causing the onset of hypoxia sooner or more frequently than at lower temperature. In reality, though, as I said and as you pointed out, I'm not sure that 82 F is really warm enough to make a difference.
And with that, I'm done hijacking this thread.
Feel free to PM me if you want to discuss further.
-S
Originally Posted by
AlwaysAisle
Yes, but hypoxia is related to the altitude, not caused by temperature. People with respiratory problems may start to experience hypoxia anywhere from 5,000 ft. altitude. For people without respiratory problem hypoxia, or altitude sickness, usually comes at altitude above 10,000 ft. The commercial aircraft we fly are set to cabin atmosphere anywhere between 4,000 ft. - 6,000 ft. altitude.
Denver, CO is located at elevation of 5,280 ft. During summer time high temperature easily reaches mid 80 F. There are many people working outside, such as construction workers, farmers, etc. Do they experience shortness of breath, headache, and anxious feelings? No, they do not. Any healthy people at 6,000 ft. altitude when temperature is in mid to high 80 F typically do not experience such symptoms. There are hundreds of passengers arriving at Denver everyday who are not accustomed to high altitude condition. Do they experience hypoxia during summer time? No they do not.
Blood oxygen level and carbon dioxide level in human blood is a function of binding coefficient with hemoglobin. Hemoglobin molecular in our blood has iron molecular in the center. Oxygen and carbon dioxide binds (secondary bonding, not covalent bonding) with iron center of hemoglobin. How efficient oxygen and hemoglobin can bind determines blood oxygen level. The chemical reaction mechanism study of oxygen and carbon dioxide with iron core of hemoglobin is exactly what us physical biochemist study. Thank you for lecturing me about what biochemist is, R&R.
I appreciate Sarfa33’s comment, but chemist in me just cannot let this go. Boyle’s Law deal with constant temperature situation. Cannot describe variable temperature conditions. To deal with temperature increase we need Ideal Gas Law (PV=nRT).
Sorry, I am not putting you down, Sarfa33. I do appreciate your comment.
Anyway, even FAA does not require pressurization of cabin when aircraft is flown below 10,000 ft. altitude. I often go up to 10,000 ft. altitude on Cessna 182, where this particular aircraft does not have pressed cabin, and not just me but everybody else are just fine.
There is a big, big difference between altitude sickness and crying and whining about the temperature.