Pulmonary blood volume and its significance in pulmonary hemodynamics immediately after mitral commissurotomy.

Immediately after mitral commissurotomy, we measured pulmonary blood volume by dye-dilution method and investigated the relationships between pulmonary blood volume and other hemodynamic parameters. Pulmonary blood volume correlated directly to pulmonary mean transit time, cardiac index, stroke volume index, and mean left atrial pressure. Pulmonary blood volume increased with mean pulmonary arterial pressures up to 35 mm. Hg but decreased with elevation above this level. The same patterns were observed in the correlations between pulmonary blood volume and both pulmonary distending pressure and pulmonary vascular resistance. These observations suggest that the changes of the pulmonary vessels begin with the elevation of mean pulmonary arterial pressure above 35 mm. Hg, pulmonary distending pressure above 25 mm. Hg or pulmonary vascular resistance above 5 units. Therefore, it is desirable to maintain mean pulmonary arterial pressure below 35 mm. Hg in patients immediately after mitral commissurotomy.