Computer model study of magnitude and phase relations of arterial pressure in response to respiratory fluctuations

A comprehensive computer model has been developed and used for studying hemodynamic waveforms and various cardiopulmonary mechanisms. Inspiratory fall of systolic arterial pressure (IFSBP) is used as an index to assess the respiratory influences on non-linear dynamics of heart rate variability. Two approaches for baroreflex regulation were tested, including a simple 1st-order relationship between R-R interval (RRI) and systolic blood pressure (SBP) and the autoregressive moving average (ARMA) model. Experimental data were obtained retrospectively from 22 patients with chronic airway obstruction before and during breathing through an external resistance. Magnitude and phase relations between arterial pressure and pleural pressure were evaluated. The computer model provided good fits to arterial pressure waveforms: correlation coefficients (r) ranging from 0.71 to 0.96 (meanplusmnSD: 0.87plusmn0.06) with a simple 1st-order model. It was observed that the ARMA model did not further improve the goodness of fit. Higher correlation coefficient between IFSBP and respiratory variation in the elderly subjects supported that aging impairs baroreflex mechanism. In terms of phase relations, no dominant parameter was found.