Dehydration and Flying

You can't afford to ignore the effects.

We all know that proper hydration is vital to good health. In the case of flying, it is even more critical. Not only is dehydration more likely at altitude and its effects more pronounced, but the consequences of losing one's competitive edge are that much more life-threatening when at the controls of a flying machine. What is dehydration?

Start with the fact that 70 percent of the body weight is water based. And 87 percent of that is inside the cell (intracellular). The "functional water" is required for oxygen enrichment and for maintaining the pH balance. Water is vital for blood, digestive juices, sweat and tears. Any discrepancy will lead to complications with delivery of these "humors," including oxygen to the body cells, creating a relative hypoxia. Complaints include: Nausea, thirst, exhaustion, muscle and joint aches, anginal pain, migraine, restlessness and most importantly symptoms such as confusion, paranoia and anxiety. Dehydration can occur as a result of high altitude, excessive exercise, sweating and water deprivation. The balance to maintain optimal body water level is coordinated by the kidneys, mostly by concentrating urine.

If the water is restricted or lost through vomiting, sweating or diarrhea, the osmotic pressure increases in the blood vessels drawing the water from the cells into the blood vessels. Similarly, at altitude, air pressure is low, the water vapor content is low and compensatory hyperventilation (increased rate of breathing) is a norm. So there is excess water loss through breathing - the exchange of dry air for moist breath. The shriveled cells slow down their function. The most damaging effect is in the brain.

Any quantity of alcohol accentuates this effect, as does smoking. A pilot cannot afford that loss of acuity. Good hydration leads to: Increased energy, reversal of cellular damage, normalization of the pH, balanced blood sugar, a fortified immune system, better sleep, clearer mind and better memory. So drink plenty of water before, during and after flight. And count a least five 8-ounce glasses of water as part of your daily goal for optimal health.

Dr. Parvez Dara, FACP, is also a Master Certified Flight Instructor, holds an Airline Transport Pilot rating and is a member of the Society of Aviation and Flight Educators (SAFE).