Volumes and breathing patterns during speech in healthy and asthmatic subjects.

The lung volumes and ventilatory patterns used by 10 healthy subjects and 14 patients with varying degrees of asthma were studied. The protocol included conversation, monologue, and counting at two loudness levels. Lung-volume changes were measured with a Respitrace and recorded with associated speech sounds. Volumes, durations, and flows were analyzed for sequences of respiratory cycles. Asthmatics used a greater percentage of their reduced vital capacity. Their inspiratory flow rates were slower, and expiratory rates faster. Asthmatics spent a greater proportion of the total respiratory cycle time on inspiration, and expired a greater volume of gas without sound. Patterns of ventilation suggested that asthmatics favored respiratory over communication needs to a greater extent than healthy subjects. Activities that forced priority to communication needs (counting to a metronome) were inadequate for gas exchange in asthmatics and could be sustained for only a limited period of time.