Pulmonary capillary blood flow studies in polycythaemia rubra vera

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Abstract
Cardiopulmonary studies were performed in 12 patients with longstanding polycythaemia rubra vera. Lung function tests indicated an increase in physiological deadspace and evidence of mismatched ventilation/perfusion relationships. Pulmonary capillary blood flow was measured by the nitrous oxide-body plethysmograph technique and a high frequency phonocardiogram was recorded from the pulmonary area to indicate pulmonary valve opening. In 10 patients the lung blood flow studies were repeated 24 hr after a 11. venesection. In the pre-venesection studies the pulsatility index of capillary flow, expressed as the ratio of peak to mean flow rates, averaged 1·6:1. The pulmonary artery to capillary flow conduction time, measured from the time of pulmonary valve opening to the foot of the capillary flow pulse, averaged 94 msec. These values were markedly reduced from normal (2·0:1 and 160 msec respectively) and indicated elevated pulmonary vascular resistance and pulmonary artery pressure. Venesection produced no significant change in the flow conduction time (mean 107 msec; P>0·10) suggesting the presence of irreversibly stiffened pulmonary arterial walls. Venesection did, however, restore the pulsatility of the capillary flow pulse to a normal level (mean 2·0:1), suggesting that there is an additional reversible component to the elevated pulmonary vascular resistance.

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