Estimation of the compliance of the human pulmonary “venous” system from pulmonary artery wedge pressure tracings

Compliance (ΔV/ΔP) of the human pulmonary “venous” system was estimated in a total of 37 human subjects, from the pulmonary artery wedge (PAW) pressure tracings, using two equations, (ΔV/ΔP) slope = 0.4·k″·SV/(v-d) given in Appendix, and k″= 0.075 PAW + 0.9 given in Method. The estimated compliance of the pulmonary “venous” system was about 7 ~ 15 ml (mmHg)^-1 in the control group, the patients of aortic valvular disease with physical capacity of Class I ~ III of the NYHA, and the patients of mitral stenosis with physical capacity of Class I. These values were in good agreement with that estimated by Guyton, i.e., 10 ml (mmHg)^-1. For the entire population of pure mitral stenosis (n = 16), compliance (ΔV/ΔP) of the pulmonary “venous” system could be related to the PAW pressure by a regression curve of ΔV/ΔP = 1/(0.0106 PAW - 0.0173). We pointed out, in discussion, that the present method and an entirely different method using the pulmonary blood volume measurements and passive leg elevation, performed in one and the same patient simultaneously, gave fairly similar values of the compliance of the pulmonary “venous” system.