Asthmatics exposed to cat allergens have decreased lung function for up to 22 hours, which is much longer than was previously believed. One reason is that the effects on the lungs can persist long after the outward symptoms resolve.
Asthma is described as an "air trapping" disease where air enters the lungs normally, but has difficulty leaving. That's why the wheezing typical of asthmatics occurs when they exhale.
Doctors at UCLA Medical School performed three high-resolution computed tomography scans (CT scans) on 10 asthmatics with cat allergies: before an exposure to cat allergens and six and twenty-two hours after the exposure. This type of CT is a safe, noninvasive way to evaluate the size and functioning of the airways.
In this small study, the effects of the cat allergen exposure persisted much longer than expected, especially for the small airways. This is significant because asthma is traditionally considered to be a disease of the larger airways. Inhaled medications easily enter the larger airways, but not the smaller ones.
The breathing of an asthmatic who is allergic to cats may be affected longer than previously thought. The detrimental effects from a cat allergen exposure may be present even though the asthmatic feels back to normal.
The newly discovered role of the small airways in asthma points to the need for new medications and inhalers that deliver extra-fine particles.
Family Practice News, 1/1/06
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