Effect of common dead space on VA/Q distribution in the dog

dead space on VA/ & distribution in the dog. J. Appl. Physiol. 68(6): 2488-2493, 1990.-Several previous studies have shown worsening ventilation-perfusion (VA/Q) relationships in hu-mans during heavy exercise at sea level. However, the mecha-nism of this deterioration remains unclear because of the cor-relation with ventilatory and circulatory variables. Our hypoth-esis was that the decrease in the series dead space-to-tidal volume ratio during exercise might be partly responsible be-cause mixing in the common dead space can reduce apparent inequality. We tested this notion in 10 resting anesthetized normocapnic dogs passively hyperventilated by increased tidal volume and a) inspired CO, or b) external dead space. We predicted less apparent VA/Q inequality in condition b because of mixing in the added dead space. After base-line measure-ments, conditions a and b were randomly assigned, and after