Semi-Quantitative Estimation of the Mean Systemic Pressure in Humans, a Preliminary Report

The mean systemic pressure was estimated indirectly in humans from cardiac index and right atrial pressure under a set of obviously over-simplifying assumptions that (1) "normal" venous return curve for mean systemic pressure (Pms) of 7 mmHg gives, by definition, a venous return of 3.8 lit.min -1M-2 at zero right atrial pressure and (2) different human subjects have venous return curves with downslopes parallel to this "normal" venous return curve. Mean systemic pressure estimated in this manner was termed the graphically estimated mean systemic pressure (Pms.g.). Pms.g. was examined for its numeric-al relationship with the cubital venous pressure (VP). In 38 pairs of comparison which was possible in 36 patients with or without heart diseases and congestive heart failure, Pms.g. tended to rise with VP. Moreover, VP tended to approach Pms.g. on the average and slightly, when the cubital venous pressure rose above the upper limit of the "normal" range, and also when the cardiac index was low, independently of the venous pressure. If the obviously over-simplifying assumptions which formed the basis of this approach are adequate, these facts suggest that the chronic congestive right heart failure, with elevated cubital venous pressure, is associated with elevated mean systemic pressure. Possible significance of the apposition between VP and Pms.g. observed for higher VP and lower CI (cardiac index) was discussed.