Comparison of theory and experiment in pulsatile flow in cat lung

A mathematical model of pulsatile flow in cat lung based on existing morphometric and elastic data is presented and validated by experimental results. In the model, the pulmonary arteries and veins were treated as elastic tubes, whereas the pulmonary capillaries were treated as two-dimensional sheets. The macro- and microcirculatory vasculature was transformed into an analog electrical circuit. Input impedances of the pulmonary blood vessels of every order were calculated under normal physiological conditions. Pressure-flow relation of the whole lung was predicted theoretically. Experiments on isolated perfused cat lungs were carried out. The relation between pulsatile blood pressure and blood flow was measured. Comparison of the theoretically predicted input impedance spectra with those of the experimental results showed that the modulus spectra were well predicted, but significant differences existed in the phase angle spectra between the theoretical predictions and the experimental results. This latter discrepancy cannot be explained at present and needs to be further investigated.