Researchers at the University of Texas Health Science Center say they have located key circuits in the brain that activate when the body begins to feel short of breath. The findings should lead to a better understanding of diseases like panic disorder, asthma and congestive heart failure, in which anxiety and stress worsen the feelings of breathlessness. In the experiments, healthy volunteers inhaled small amounts of carbon dioxide while researchers used positron emission tomography, or PET, scans to investigate what areas of the brain are involved in the perception of breathlessness.
PET scans track blood flow in the brain and show which areas become active during selected tasks.
Breathing is one of many automatic functions of the body that for the most part take place in the background, outside of conscious thought. Scientists have long known that automatic breathing activity is centered in the brain stem. What is not understood, the researchers say, is what happens in the brain as individuals become aware of their breathing. In the experiments, researchers used face masks or mouth tubes to control the mixture of air given to subjects. After starting with pure oxygen, researchers switched to a mixture of about 8 percent carbon dioxide - not enough to induce ill effects in the body, but enough of a change to trigger a reaction in the brain.