Effect of parenchymal shear modulus and lung volume on bronchial pressure-diameter behavior.

A method that interrelates lung pressure-volume behavior, bronchial pressure-diameter behavior, and parenchymal shear modulus is presented. The method was used to predict changes in intraparenchymal bronchial diameter that occurred when lobe pressure-volume behavior and parenchymal shear modulus were markedly changed by inducing air trapping in isolated dog lobes. Predictions agreed with measurements, thereby supporting the general method. Measured values for the shear modulus were approximately 0.7 times the transpulmonary pressure for the control state. Estimated values for the peribronchial pressure difference from pleural pressure during a deflation pressure-volume maneuver for transpulmonary pressures below 12 cmH2O were small, approximately +/- 1 cmH2O, its sign being positive or negative, depending on whether the bronchus was dilated or contricted.