NEW ORLEANS, Nov. 15 – Having 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 today at the American Heart Association’s Scientific Sessions 2000.
“There are many reports that in-flight medical emergencies are generated at the rate of one person per 800 to1,900 flights,” says primary researcher Makoto Matsumura, M.D., of the Saitama Medical School in Japan. More than half of these involve 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 is the first to evaluate the role of food and fluids in preventing fainting and heart attacks in air travelers. The researchers say that eating and drinking before boarding was expected to raise the volume of blood circulating in the body.
“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’t eat or drink before boarding,” says Matsumura. “Medical personnel and travelers should know that hunger can cause in-flight emergencies, and fluid is probably even more effective in preventing emergencies. Older individuals and those with high blood pressure or vascular disorders are especially at risk for these types of emergencies.”
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 its oxygen supply. However, the amount of blood pumped by the heart remains the same. Therefore, everyone on the plane – from infants to the elderly, crew and passengers – could have a relative reduction in oxygen supply throughout their bodies.
“Many people experience an unpleasant feeling in-flight. I sometimes get a headache or feel cold or tired, which is similar to the slight sickness caused by low in-flight air pressure. Treatment is usually unnecessary. However, in some cases, a doctor is needed during a flight in case the person is having a heart attack,” says Matsumura. “We wanted to know what causes this oxygen reduction.” 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, says Matsumura.
The study was performed in a hypobaric (low barometric pressure) training laboratory for Japan’s Air Force pilots in which barometric pressure can be completely controlled. Researchers simulated conditions equal to the pressure of a flight to 10,000 feet. Using non-invasive measures, they measured heart function, blood flow and oxygen saturation of both brain and organ tissues in 12 normal volunteers. The tests were performed after a 12-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 4 mm/Hg, and oxygen saturation decreased in the peripheral arteries by about 11 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 21 percent, and in the brain by 48 percent over the fasting individuals.
So how much do people need to eat and drink to ward off an emergency situation?
“It is a difficult question to answer,” Matsumura acknowledges. “We asked the volunteers to have at least 16 ounces of a soft drink with electrolytes at lunch. Then we measured their body weight. The average weight gain after lunch was about 2.5 pounds, which is appropriate in normal cases. If a large amount of food and fluid increases the circulating volume too much, it may induce heart failure in people who have heart disease.” Electrolytes are molecules of calcium, potassium, sodium and other elements that gain a slight electric charge when dissolved in water and are involved in the normal function of the body’s cells. These substances are often added to sports drinks.
Researchers plan to increase the number of subjects in future studies that will test the content and volume of food and fluid intake against changes in oxygen saturation and blood flow.
Co-authors are Ryozo Omoto, Shunei Kyo and Akio Nakamura.