The effect of intermittent positive pressure breathing and voluntary hyperventilation upon the distribution of ventilation and pulmonary blood flow to the lung in chronic obstructive lung disease.

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Abstract
Studies were made on 14 patients with chronic obstructive disease of the lungs at rest, during intermittent positive pressure breathing, and during voluntary hyperven-tilation. Changes in arterial blood gases measured during air breathing are correlated with changes in N washout curves during O2 breathing. Both intermittent positive pressure breathing and voluntary hyperventi-lation had the same effect on arterial blood gases, raising arterial O2 saturation to a normal value, and lowering arterial CO2 tension to as subnormal value. During both procedures, there was an increase in O2 consumption that was about 4 times as much per liter of added ventilation during voluntary hyperventilation as it was during intermit-tent positive pressure breathing. During intermittent positive pressure breathing, about 1/10 of the extra ventilation was directed into the slow space. This was enough to account for the observed rise in arterial O2 saturation. During voluntary hyperventilation the increase in the ventilation of the slow space was less than 1/10 and was not enough to account for the rise in arterial O2 saturation. This suggests that during voluntary hyperventilation the rise in arterial O2 saturation was partly due to a reduced fractional perfusion of the slow space.