Aeromedical Forum

Have you ever thought that flinging yourself through the air at several hundred miles an hour, several miles above the earth in a tiny cylinder of aluminum is a bit odd? Probably not.

You're a pilot and flying is the best thing conceivable. However, your body may not agree with you. Even in the most modern of commercial aircraft, the environment is not what you normally experience on your front porch.

The cabin altitude is usually around 8,000 ft. MSL, a big jump for us Midwesterners. Oxygen saturation can drop between 6 and 25 percent. The cold, dry air sucked into the cabin has humidity lower than some of the driest deserts. That, of course,e is what we experience in a transport category aircraft.

A General Aviation aircraft can be an even more hostile environment. A case in point, few years ago, my wife and I were flying back from Bozeman, Montana (KBZN). After a great week of skiing, we were anxious to get home. Weather was clear all the way back to Minnesota. We had a nice tailwind at 17,000 ft. We strapped on the oxygen, leaned her back to maximum economy, and set down in the Twin Cities some five uneventful hours later.

I was glad I could do a visual with the wind straight down the pipe as I was not feeling particularly sharp. Hypoxia wasn't an issue as I'd been monitoring my O2 saturations. Fatigue was definitely a factor and there were a number of things that may have been contributing to it.

Quite a bit of research has been published over the past few years on effects on the human body of prolonged flight. Hypoxia is, of course, a well-known issue. Even at 5,000 ft. night vision can be impaired. Pressure altitudes above 7,000 ft. have been found to increase reaction times. That might be a concern when ATC tells you to change course "without delay."

Short term exposure to altitudes of at least 10,000 ft. can increase fatigue. Above 12,000 ft., without supplemental oxygen most folks will have some degree of mental impairment. It's initially subtle but when you're trying to fly an airplane, that's significant.

Then there's the dry skin thing. Some Austrian researchers reported that a long-distance flight at airline cabin pressure (8,000 MSL or so) can reduce the moisture content of your skin by up to 37 percent, leaving you flaky and itchy. That can be a major distraction.

The British Aerospace Medical Association recently reported that for some folks at cabin altitudes as low as 6,000 to 8,000 ft. anxiety levels can increase, as can emotional liability.

Mild dehydration, so often seen in GA flights has also been shown to influence mood. Professor Stephen Legg at Massey University in New Zealand recently summed it up: "We know very little about the effect of exposure to multiple mild stressors on complex cognition and mood. But we do know that there is a general 'fatigue' associated with long distance air travel, so I guess it is probably the combined effects of these concurrent multiple mild exposures that may give rise to 'flight fatigue'."

So, what can a pilot do to minimize the effects of flight fatigue? Here are a few suggestions:

• Consider using oxygen liberally on long flights; at or above 7,000 to 10,000 ft. during the day, 5,000 ft. at night.

• Monitor 02 saturations, especially when you are at or above 10,000 ft. Try to keep sats at or above 95 percent , 90 percent at a minimum. If it goes below that, ask ATC for lower altitude.

• Keep yourself hydrated. Pack a couple of water bottles in the cockpit. I know...there's no lave in a Piper Arrow. Pack in a milk carton too!

• Make sure you're well rested and healthy before the flight. Remember the I'M SAFE checklist.

• Carefully preflight for weather and in-route challenges. If you're thinking about flying in the clag for 5 hours, shooting an approach to minimums and possibly going missed, think again! You might want to postpone that flight.

Fly wisely. See you next month!

As always, comments, questions and suggestions are welcome: jdlakin@mnallergyclinic.com.