At age 18, I was a lifeguard and a pool operator in my hometown of Berwyn, Illinois. Sometimes before the pool opened, I would swim alone - the length of the pool twice, underwater. I’d hyperventilate to get the CO2 in my blood low so that I’d not sense what some of us think of as oxygen hunger. Really bad idea! My stress signal was the buildup of CO2, but the real danger is lack of O2…and our bodies don’t sense that.
Competitive swimmers and divers have died from hyperventilating and breath-holding. Yet, free-diving seals hold their breath for minutes. They surface before they run out of oxygen and pass out. What’s their trick, asked J. Chris McKnight and his 8 colleagues in Scotland? Simple, though not possible for us: Their neural pathways in their brains are mostly more sensitive to oxygen levels than to CO2 levels. The researcher team has seals diving for food after breathing ordinary air, air with low O2, or air with high CO2. The seals responded to the O2 level. High CO2 had little effect; the acidification of their blood by CO2 was counteracted by biochemical “buffering.”
We humans need SCUBA or CO2 scrubbers; seals evolved a special physiology to be masters of the dive.
This has been an outreach activity of the Las Cruces Academy, viewable at GreatSchools.org.
Source: Science 21 Mar. 25, pp. 1276 ff.
Image: NOAA Fisheries
