Magazine article Science News

Tracking the Cause of Asthma's Wheeze

Magazine article Science News

Tracking the Cause of Asthma's Wheeze

Article excerpt

Until recently, scientists believed that asthma resulted when muscles surrounding the lung's airways went into spasm, restricting the flow of air. But a computer study augments recent evidence that inflammation and thickening of the airway tubes is the chief cause of an asthmatic's wheezy breathing.

Mathematician Barry R. Wiggs and his colleagues at the University of British Columbia in Vancouver turned to a computer model of the human lung in their search for the underlying cause of asthma. First, the team obtained data on the thickness of airway walls by studying tissue removed at autopsy from the lungs of people with severe asthma. The researchers gathered further data on airway walls by looking at lung tissue removed during surgery from people without asthma. Compared to the controls, the asthmatics' airway tubes were severely thickened by the effects of chronic inflammation.

Next, the Canadians plugged the data into the computer model. When the team simulated the constriction of the smooth muscles surrounding the airway tubes, they found some airflow resistance. That's to be expected, says Wiggs, who notes that a person with healthy lungs experiences some resistance to airflow when bronchial muscles constrict. Most people might notice a little more difficulty breathing but wouldn't experience any discomfort, he adds.

When the team looked at a model of an asthmatic lung, with its thickened and inflamed airway walls, a dramatic increase in airflow resistance occurred with the same constriction of smooth muscles, he says. …

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