On relationship between bulk modulus and relative volume of lung during inflation-deflation maneuvers

An equation of the form K=C/[1 - (V/V max)]n relating the bulk modulus K to the relative volume V/V max of lung region during inflation-deflation maneuvers is proposed. It well represents the observed fact that the bulk modulus becomes infinitely large when the regional volume approaches its maximum capacity V max. The parameter C describes the bulk modulus at low regional volume whereas the parameter n quantifies the rate at which the bulk modulus changes during the inflation-deflation maneuvers. The mathematical expressions for the regional pressure, P, and volume V , are obtained by integrating the equation K=VdP/dV. They fit exceedingly well with the experimental data recorded during inflation-deflation tests of six excised canine lung lobes.