"Pure oxygen can reduce blood flow to organs and tissues by increasing ventilation," Dr. Steve Iscoe, a respiratory physiologist, explains. "The increase in ventilation, which is almost never considered, 'blows off' carbon dioxide, and this fall constricts blood vessels. When carbon dioxide is added, however, the blood vessels dilate, increasing blood flow and causing more oxygen to reach tissues in key areas like the brain and heart."
"It's puzzling that a simple idea like this has received so little attention from clinicians," says Dr. Iscoe. Although there has been some concern about the possibility of patients receiving too much carbon dioxide (which can cause discomfort), he points out that new designs for oxygen masks allow precise monitoring of levels delivered or, in fail-safe mode, prevent inhalation of carbon dioxide. One can even use the patient's own expired carbon dioxide, the researcher adds.
"The reduction in oxygen delivery to the foetus, the brain, the heart, and other body tissues that might be induced by oxygen administration is, as this paper points out, largely unrecognised even by respirologists such as myself," says Dr. Peter Macklem, professor emeritus of medicine at McGill University.
Iscoe hopes to evaluate the promise of the new technique in a study of diabetic patients. As the incidence of obesity rises, diabetes is expected to affect a growing number of people and exert increasing demands on the health care system.
"I think it's incumbent on health professionals to consider carbon dioxide when administering oxygen, since we know that carbon dioxide levels control blood flow to so many parts of the body," Dr. Iscoe says. "We should look at carbon dioxide not as an enemy, but as an ally."
MEDICA.de; Source: Queen's University