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Fill Up on Fluids

by Paul Engstrom, Aviation Writer and IFA Member

It was a hot summer day as the private pilot, drenched in sweat, flew toward home after numerous stressful landings at several airports. Suddenly, he felt disoriented and spacey, and became alarmed when he couldn't recall the number of the runway he had used hundreds of times at his home port.

Only after this pilot was safely on the ground did he pinpoint the culprit: dehydration. His symptoms aloft, he recalled, were the same as those he had experienced many times after grueling aerobic workouts at the gym without drinking enough fluids.

Many pilots aren't aware that prime-time flying'often during the warm or hot months'is when dehydration can erode their dexterity, coordination, ability to make quick decisions, alertness and visual capabilities, or that it causes fatigue.

Perhaps even fewer are aware that many things besides hot weather can rob a body of the fluids it needs to stay ahead of the demands of flying. They include:

  • Vigorous exercise before a flight
  • A warm cockpit
  • Diuretics'drinks like coffee, tea, alcohol and soda, which boost the production and excretion of urine
  • Wind
  • High humidity
  • A change in climate
  • Sunburn
  • Fever
  • Antihistamines
  • Diarrhea and vomiting
  • Diabetes

Our bodies normally lose 3 to 4 pints of water a day through sweating, breathing and urinating, according to Dr. Richard Rinehart, a FAA senior aviation medical examiner. That rate increases within minutes after takeoff in a dry cockpit, especially if it's pressurized.

'And what's the first thing you request after reaching cruise?' Rinehart says. 'Coffee, [caffeinated soda] or tea, all of which are diuretics'that will exacerbate the problem.'

Keep in mind that water makes up about two-thirds of body weight. It plays a crucial role in cell division, transportation of nutrients, elimination of wastes and regulation of body temperature. In a person who weighs 170 pounds, there are more than 10 gallons of water in and around the cells and in the bloodstream.

Depending on individual physiology, temperature, activity level and other factors, most people become thirsty after they shed around 1.5 quarts of water, or 2% of total body weight, says Rogers V. Shaw, team coordinator of the Airman Education Program at the Civil Aerospace Medical Institute in Oklahoma City, Okla.

The problem, Shaw notes, is that the thirst mechanism 'arrives too late and is turned off too easily.' In other words, a pilot might already be dehydrated by the time he or she realizes it and may consume too little fluid to compensate.

Dehydration is serious enough that in 2002 the FAA added it to the list of aeromedical factors about which student pilots must be familiar in order to meet the Practical Test Standards for a private license.

The danger hasn't gone unnoticed in commercial aviation circles either. Dr. Don Hudson, an aeromedical adviser to the Air Line Pilot Association, emphasizes dehydration risks in meetings with pilots who fly for a living.

This doesn't mean you have to make rehydration a science, calculating down to the fluid ounce how much water you'll need. The Federal Air Surgeon's Medical Bulletin simply advises drinking lots of cool water, not waiting until the thirst sensation kicks in and avoiding diuretics. Having an ample supply readily accessible before and during a flight will probably do the trick.

If bottled water is too unpalatable, try a sports drink like Gatorade. These drinks contain electrolytes'potassium, calcium and sodium'that muscles and nerves rely on for carrying electrical impulses. Sodium also helps the body retain fluids.

The bottom line: Fly safe'and never pass up an opportunity to consume fresh water.

When he isn't flying, Paul Engstrom writes and edits from Sebastopol, Calif.