Curve-fitting analysis of pressure-volume characteristics of the lungs

The pressure-volume relationship of the mammalian lung is markedly curvilinear and in the normal lung, can be shown to fit an exponential function of the form V = V0(1 - K 0e-K1P) in the range of lung volume from FRC to TLC. A method is presented, using a programmable calculator, of determining the parameters V0, K0, and K1, and of deriving related constants of greater physiological significance. Values calculated from pressure-volume curves of 20 normal human subjects are listed, together with coefficients of determination, to demonstrate the adequacy of fit of the method. Half-inflation pressure (h- ln 2/K1), ranged from 2.65 to 9.21 and coefficients of determination (r2) ranged from 0.851 to 0.9998.