April 27, 2005 -- A small U.K. study reports that as a result of changes in cabin pressure on commercial airplanes, oxygen levels drop to a degree that is potentially dangerous for people with heart and lung problems.
The study, which appears in the journal Anaesthesia, measured blood oxygen levels in 84 passengers (aged 1-78) before and during flights. The flights were at least one hour long, with a maximum altitude of 27,000 to 37,000 feet.
On the ground, the estimated oxygen levels of participants were normal; at cruising altitude, the levels dropped 4%, the study says.
For healthy people, a 4% dip in oxygen saturation might not be noticeable. However, for people with heart and lung conditions this can result in a dramatic and dangerous drop in blood oxygen. Many people with heart disease such as heart failure -- or lung disease like emphysema -- may already suffer from low levels of blood oxygen. Changes in cabin pressure might affect them more and worsen their existing condition.
Fifty-five people flew on long-haul flights (two hours or more). The other 29 passengers flew for 1-2 hours. Passengers flew on more than 10 commercial airlines, say the researchers.
"There was a statistically significant reduction in oxygen saturation in all passengers traveling on long-haul and short-haul flights" when compared with oxygen levels on the ground, write the researchers, who included Susan Humphreys, anesthetic specialist registrar with The Royal Group of Hospitals in Belfast, Northern Ireland.
More than half (54%) of the passengers' estimated oxygen levels were significantly lower at cruising altitude than at ground level, says the study.
The researchers say the drop in oxygen is "a value which may prompt physicians to administer supplemental oxygen in hospital patients," and over one-third of respiratory physicians would do so.
No Major Problems Reported
The study doesn't show any health problems among participants during the flights. However, many passengers may be unaware of the health consequences associated with flying.
There are guidelines on travel for people with chronic illnesses, including the requirement for supplemental oxygen for travel. Participants in the study did not have severe heart or breathing problems and didn't need a doctor's permission to fly.
No record was made of whether participants were smokers.
Age mattered. Lower oxygen levels during air travel were seen in all age groups, but "older people started low and ended low," says the study.
Low oxygen levels in susceptible people may lead to life-threatening heart problems or chest pain, write the researchers.