EFFECT OF ADDED DEAD-SPACE ON PULMONARY VENTILATION DURING SUB-MAXIMAL, STEADY-STATE EXERCISE

¹ Department of Physiology, University of Aberdeen, Aberdeen, Scotland

Six normal subjects exercised for 6 min at 30%, 50%, and 70% of their predicted Vo₂max, with and without an added respiratory dead-space of 1,200 ml. The added dead-space caused a marked increase of V₂/MVV₁₅%, the values at the three work loads being, respectively: without dead-space, 20·4%, 30·1%, and 44·2%; and, with dead-space, 41·1%, 48·6%, and 68·7%. These increases of V₂ were due mainly to increases of tidal volume, but ventilatory frequency increased also, the values being: without dead-space, 21·0, 25·5, and 30·4 breaths/min; and with dead-space 25·4, 28·4, and 33·9 breaths/min. At the highest work load the V₂/VC ratio without dead-space was 44·0%, and with the dead-space 62·6%. Possible reasons for the breathing pattern adopted by the subjects are discussed.

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