Abstract
In order to define more clearly the ventilatory, circulatory and mechanical alterations attendant upon application of an external expiratory airway obstruction during exercise, study of blood gas tensions, end-tidal trap gas tensions, ventilatory variables and diffusing capacity under such conditions has been carried out. Significant changes in Pa O 2 , Pa CO 2 , tidal trap gas composition and ventilatory factors were observed. Lack of variation in pre- and post-obstruction A-a O 2 gradients and calculated physiological dead space implies that definable disturbances in ventilation-perfusion relationships are not occurring. Existence of a negative a-A CO 2 gradient during steady-state exercise is confirmed and a magnification of the gradient during resistance breathing demonstrated. Comparison is made of arterial blood gas, end-tidal trap, and continuously monitored end-tidal CO 2 tensions. No alterations in diffusing capacity were detected.
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