MINUTE VENTILATION IN ASTHMA - ENHANCEMENT BY MOUTHPIECE AND DEPRESSION BY OXYGEN ADMINISTRATION

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Abstract
To evaluate independently the effects of an inspiratory stimulus (a mouthpiece) and a ventilatory depressant (O2) on minute ventilation (.ovrhdot.VE) in asthma .ovrhdot.VE was measured with magnetometers in 18 asthmatic subjects. When room air was inspired from a loose-fitting mask, .ovrhdot.VE was 10.2 .+-. 0.6 l/min. When O2 was substituted for room air .ovrhdot.VE decreased (8.4 .+-. 0.6). When O2 was given by mouthpiece, .ovrhdot.VE increased (12.9 .+-. 0.7). In the clinical setting, the mouthpiece artifact may operate to exaggerate the tidal breath or to obscure the effect of a respiratory depressant (e.g., O2) upon the measurement of resting ventilation.