NEW ORLEANS?aving a quick snack and a non-alcoholic drink before boarding a plane can lower your chances of becoming an in-flight emergency statistic, according to a study presented last month at the American Heart Association? Scientific Sessions 2000.

"There are many reports that in-flight medical emergencies are generated at the rate of one person per 800 to l,900 flights," said primary researcher Makoto Matsumura, M.D., of the Saitama Medical School in Japan.

More than half of these involves the loss of consciousness and heart attack. Factors such as anxiety, the environment inside the cabin, dehydration, prolonged sitting and alcohol use have been suggested as causes of these emergencies, but no one has researched these explanations or how the problem can be prevented.

This study evaluated the role of food and fluids in preventing fainting and heart attacks in air travelers.

"Having something to eat and drink is the simplest method of increasing the circulating blood volume for air travelers. Most are probably doing it before boarding anyway, but people need to know it is easy for their bodies oxygen levels to drop if they don? eat or drink before boarding," said Matsumura.

Researchers theorized that in-flight fainting spells and cardiopulmonary emergencies could be related to a change in blood-circulation. Low cabin pressure at higher altitudes causes blood vessels in the peripheral circulation and organs to expand as the body attempts to increase it oxygen supply. Everyone on the plane?rom infants to elderly, crew and passengers?ould have a relative reduction in oxygen supply throughout their bodies.

Blood pressure does not change if the circulating blood volume is high enough. However, it is possible to have a blood pressure decrease and oxygen deficiency in the organs if the amount of blood circulating in the body is too low to accommodate expanded blood vessels, and this may be affected by dehydration, said Matsumura.

The study was performed in a hypobaric (low barometric pressure) training laboratory for Japan? Air Force pilots in which barometric pressure can be completely controlled. Researchers simulated conditions equal to the pressure of a flight to l0,000 feet.

The tests were performed after a l2-hour fast and after eating and drinking.

In the fasting volunteers reduced cabin air pressure caused no change in heart function or blood flow volume, but blood pressure decreased by about 4mm/Hg, and oxygen saturation decreased in the peripheral arteries by about ll percent, and in the brain by about 6 percent.

Eating and drinking caused no significant change in blood pressure, but it did increase cardiac output and blood flow to the brain as tracked through the right carotid artery. Food and fluid intake also improved the levels of oxygen in the peripheral organs by 2l percent, and in the brain by 48 percent over the fasting individuals.