Trux, I think hypercapnia causes diaphragm contractions, gasping and urge to inhale (actually urge to exhale). I don't think Hypoxia triggers any of those.
Yes, of course, that's exactly what we are speaking here about.
However, the paper by Ramirez et al that I linked earlier, and some other papers discussing infant gasping, specifically discussed hypoxia being significant, and said nothing about hypercapnia.
The paper definitely does not claim that hypoxia is responsible for gasping. You have to read scientific texts carefully - each word and each formulation are important, and extrapolating the facts beyond the original claims is dangerous, but unfortunately it happens often when scientist work is interpreted by journalists to the public.
In this case, all what the paper tells is that there are two different neuronal groups responsible for the breathing pacemaker mechanism, and that one of them shuts down
during hypoxia (not
due to it!), while the other remains active. They definitely do not tell that the gasping reflex is triggered by low oxygen level in the blood. They only tell that when the hypoxic type of the neuronal system does not work at babies, and the baby accidentally falls into hypoxia, no gasping follows and that causes the SIDS. There is not one word telling it is the low oxygen level that triggers the gasping with one or the other neuronal system. They only explain it happens during hypoxia. Hypoxia is normally always accompanied with hypercapnia (unless you are breathing another gas, or hemoglobin cells in blood are insufficient or damaged).
Although are of course right, it is incorrect to interpret is so that the urge to breath is caused by hypoxia or that hypercapnia is unimportant for the breath control. Quite oppositely - in fact it shows the importance of hypercapnia. While hypoxia shuts down one of the two neuronal pacemaker systems, it means that the role of CO
₂ is even more important, because under hypoxia only one of the two redundant pacemaker system works. So if you manage to shut down the second one by artificially lowering the CO₂ level, you are really in troubles.
Trux, BTW, when you type CO2, it appears (on my screen anyway, I don't know about other people's) like CQ. At first, I didn't know what you meant, I thought you meant Carbon Quotient. Perhaps it is a software translation bug? The 2 sits directly beneath the letter, rather than offset to the right.
That's a subscript 2 as it correctly ought to be used at chemical formulas. If the subscript 2 does not display properly on your computer, then you probably have outdated Unicode fonts. DeeperBlue forum uses (preferentially) the Verdana font, so you may consider downloading an up-to-date version of that font for your system. As for MS systems, you can get it directly
from Microsoft here, and for Macs for example
here. You'll find free Verdana fonts on the web also for other OS's.
