Asthma.

Wheezing, chest tightness, increased effort to breathe, and decreased exercise tolerance are common symptoms of asthma. Not all asthma patients wheeze, however, and some people with asthma cough. Sleep disturbance can be another unrecognized symptom. Ware G. Kuschner, MD, explains what to look for when diagnosing atypical asthma in adults in his 1999 article for Postgraduate Medicine. He says that absence of wheezing can be a serious sign in people with asthma: "In very severe, life-threatening exacerbations of asthma, airflow may be reduced so significantly that no breath sounds can be heard on auscultation and wheezing is inaudible." Properly administered bronchodilator therapy can help differentiate between asthma and other conditions with similar symptoms such as pneumonia, emphysema, and congestive heart failure. If a cough or other symptoms improve with bronchodilator therapy, asthma is probably the correct diagnosis. Diagnosis becomes more complicated when severe airway obstruction prevents an effective amount of medication from entering the bronchial tubes.

Pulmonary function testing is a more formal way to diagnose asthma. This test measures the change in the amount of air a person can forcibly exhale after using a short-acting bronchodilator. The test indicates asthma when forced expiratory volume in one second (FEV1) increases by 200mL and by 12% from baseline after bronchodilator use. (No bronchodilator therapy should be used for at least six hours before pulmonary function testing.) Dr. Kuschner does not advocate using arterial blood gas measurements. "Significant abnormalities are not typical in uncomplicated mild or moderate asthma; indeed, blood gas values may be normal or near normal even during severe exacerbations," he explains.

Dr. Kuschner says that workplace triggers play a factor in up to 20% of adult-onset asthma cases. Triggers can constrict bronchial tubes and produce chest tightness within minutes. A late response of four to six hours after exposure to a trigger is also possible. "An occupational association is suggested when symptoms and PEFR [peak expiratory flow rate] worsen during working days and improve during long weekends and vacations," he writes. PEFR measures the airflow from a forced exhalation with a small handheld device: "... a difference greater than 20% between measurements suggests asthma." PEFR can also be used to identify specific asthma triggers. Avoiding triggers, whenever possible, prevents asthma exacerbation.

Kuschner WG. Ten asthma pearls every primary care physician should know. Postgraduate Medicine. September 1999;106(3). Available at: www.postgradmed.com/issues/1999/09_99/kuschner.htm. Accessed February 6, 2008.

briefed by Jule Klotter