Winter Flying

Another word about hypoxia, it gets hard to read the altimeter! With winter power increases, due to colder air and without the burden of floats, one naturally flies higher and with good reason. See "The Mountains Grow Taller in Winter." Unfortunately density altitude does not help our pulmonary physiology much at all, and we may experience surprising hypoxia at easily achieved altitudes. The regulations vary by category. The 12,500 foot restriction for part 91 and the 30 minutes between 12.5 and 14,000ft are marginal at best. Part 135 and part 21 are more restrictive. As you get older, you may experience loss of cognitive function for prolonged flights above ten. Emphatically, the nasal cannula is near worthless, and so is sucking on the tube. Why? It's the CO2 thing. Your respiratory drive wants to conserve CO2 at altitude by breathing slower, thus reducing pulmonary O2 levels. You need the rebreather bag, big time, and positive pressure (military oxygen systems) in the flight levels.