THE DETERMINATION OF UNEVEN PULMONARY BLOOD FLOW FROM THE ARTERIAL OXYGEN TENSION DURING NITROGEN WASHOUT

Abstract

A new method is described for obtaining quantitative data on distribution of pulmonary capillary blood flow through well and poorly ventilated regions of the lungs. It requires continuous or repeated analyses of alveolar PN2 and arterial PO2 during inhalation of O2. End-capillary PN2 is calculated from the arterial O2 tension during the N2 washout. The ratio of PAN2 to PCN2 late in the washout gives the ratio of fractional ventilation to fractional per-fusion through the poorly ventilated space. Unevenness of perfusion exists when the fractional perfusion is in excess of fractional ventilation to the poorly ventilated space. Normal subjects have no uneven-ness of perfusion in relation to ventilation. Patients with emphysema have marked unevenness of perfusion in relation to ventilation but not in relation to lung volume. Patients with interstitial fibrosis may have unevenness of perfusion in relation to ventilation. Patients with mitral valvular disease and pulmonary hypertension have unevenness of perfusion in relation to ventilation.