Dear Readers:
Lungs and Gas Exchange
The truth be told, normal lungs are not the limiting factor in gas exchange- even if bubbles are present. If someone has emphysema, then we are talking about something else. Here an individual would have a high degree of ventilation (= air in and out) in essentially useless air sacks (= alveoli) because they are too large and not supplied well with blood capillaries. This is not your normal diver. Divers are healthy individuals.
The blood supply to the lungs is seldom a limiting factor (if ever) in a healthy individual. When we are running and huffing and puffing, our ability to sustain the fast pace is not because we are not getting enough oxygen or eliminating enough carbon dioxide through the lungs. The limitation is within the muscles themselves. This is cured through training and is also influenced by genetics. Some folks are walkers, some distance runners, and some are sprinters. :crawl:
Perfusion
Blood flow in the legs is influenced by body position on dry land. There is a hydrostatic (= pressure) gradient when you are in air (and gravity) and blood pools in the legs. If you are reclining, this gradient is gone. When you are in water, the gradient does not exist. Perfusion is not a function of body position in the water.:mean:
Exercise
The key to better gas exchange is exercise in the arms and legs. This is not theoretical. The gas-exchanged properties of exercise are documented and quantified. We use them all the time at NASA to prepare astronauts for space walks (=EVA).
Dr Deco :doctor:
