Hyperventilation is a characteristic feature of acute asthma. In all but the most severe, life-threatening episodes, increased alveolar ventilation is marked by lowered arterial carbon dioxide tension. Perhaps for this reason, respiratory rate is recorded in emergency room charts. However, investigations of respiratory rate in asthma have not shown clearly that hyperventilation is accompanied by an increased respiratory rate. Tobin et al observed normal respiratory rates in ambulatory, symptomatic asthmatic patients; Woolcock reported that their breathing was rapid and shallow, while Camazine thought that slow, deep breathing was the most appropriate and commonly observed pattern.
The present study was designed to see whether we could reconcile these conflicting opinions. We wanted to know whether or not the respiratory rate was increased in asthma and whether the routine monitoring of it might be useful. We therefore assessed breathing pattern in asthmatic patients under the following three conditions: (1) spontaneous severe asthma treated in the emergency room; (2) methacho- line-induced bronchospasm; and (3) exercise-induced bronchospasm.
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