HADERA, ISRAEL —Patients who have a low perception of dyspnea (POD) are at increased risk for near-fatal or fatal asthma attacks, even if they have no history of life-threatening episodes. A recent study reveals that 29 of 113 outpatients (26%) with stable asthma had a blunted POD.[1]

During the two-year follow-up, these patients were significantly more likely than those with a normal or high POD to visit the emergency department, be hospitalized, or have near-fatal or fatal asthma episodes, said Paltiel Weiner, MD, one of the principal investigators. Dr. Weiner is Head of the Department of Medicine A at Hillel-Yaffe Medical Center in Hadera, Israel.

RESPIRATION AGAINST INCREASING RESISTANCE

All patients in the study met the American Thoracic Society definition of asthma—reversible airflow obstruction documented in at least one pulmonary function study and episodic wheezing, coughing, or shortness of breath that is alleviated by bronchodilation. Patients with a known history of near-fatal asthma were excluded from the study.

The investigators measured the POD with a two-way valve designed to provide increasing resistance. The patients breathed through the valve against progressively greater loads for one-minute intervals to achieve mouth pressures of 5, 10, 20, and 30 cm H2O.

At baseline and after each interval, the patients scored their dyspnea from 0 (none) to 10 (maximal) on the modified Borg scale; a normal POD was defined as the mean Borg score (within one standard deviation) of 100 age- and sex-matched controls. The patients received regular follow-up for at least 24 months.

MORE MONITORING, TREATMENT

POD was normal in 67 (59%) of the patients, high in 17 (15%), and low in 29 (26%). There were 13 near-fatal asthma episodes and six deaths among those with a low POD; only four episodes of near-fatal or fatal asthma occurred in the other two groups combined.

Patients with a low POD tended to be older and female and to have a longer duration of asthma. These patients, as well as those with high POD, were significantly more likely to have severe asthma than were patients with a normal POD. The patients with a low POD, however, used b2-agonists less often and had a lower mean peak expiratory flow than did the patients with a high POD. There was no link between POD and forced expiratory volume in one second, age, or asthma duration.

Because a low POD clearly raises the risk of near-fatal and fatal asthma, Dr. Weiner recommended that all asthma patients have their level of dyspnea tested with his method or with methacholine challenge. He added, “Those with a low POD should be monitored more carefully, treated more often, and educated about self-management. They should measure their peak flow in the morning and evening and contact their physician when they see a decrease.”

—Timothy Begany

Reference
1. Magadle R, Berar-Yanay N, Weiner P. The risk of hospitalization and near-fatal and fatal asthma in relation to the perception of dyspnea. Chest. 2002;121:329-333.

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