Relaxation Compliance and Relaxation Viscous Resistance of the Human Lungs

Abstract

The four-element maxwellian model was introduced into the analysis of stress relaxation of the lungs. Solving the equation: P(t)=P_res+P_rel•e^-t/T, relaxation pressure, relaxation time constant and residual pressure were measured to obtain relaxation compliance, relaxation resistance and residual compliance of the lungs. Furthermore, since the lung tissues were supposed to consist of many maxwellian elements, the pressure was expressed as the equation : P(t)=∫^+∞_-∞F(log)•e^-t/T d log T, where F(logT) was the logarithmic distribution function of the relaxation time constant, and it was demonstrated that F(logT) roughly agreed with the relaxation time constant in the four-element model. The relaxation pressure had a rather remarkable magnitude in healthy subjects in comparison with patients with chronic obstructive lung diseases, and relaxation compliance and relaxation resistance showed no correlation with visco-elastic properties of the lungs.