Cardiopulmonary model to study interaction hemodynamics in Muller maneuver

摘要

The Muller maneuver (MM) is a frequently used physiological test in evaluating the cardiopulmonary (CP) interactions along with baroreflex functions in human. In spite of extensive experimental efforts, there is still ambiguity, controversy and disagreement in explaining different aspects of underlying mechanisms during MM. So far a complete comprehension of these mechanisms and the interactions among them is unavailable. In the present study, a CP model with detailed representation of cardiovascular, respiratory and baroreflex system is developed for the purpose of complete, continuous and simultaneous monitoring of all above three systems in MM to explain the underlying mechanisms. Our model incorporates the advantages of various models of all three systems reported separately in literature. Effective coupling is realized by intrapleural pressure between cardiovascular system and respiratory system Baroreflex regulation on cardiovascular system is achieved through vital cardiac parameters such as cardiac duration, contractility and peripheral resistance. Initially, the CP dynamics are tested qualitatively by simulating quiet breathing. Quiet breathing is simulated by perturbing intrapleural pressure in an exponential way from -3.7 to -5.5mmHg. The quantitative analysis of CP interaction is studied by simulating MM in which strong intrapleural pressure variation is realized. The developed model can predict significant physiological events in individual system dynamics along with their interactions in quiet breathing condition as in literature data. In MM, simulated arterial pressure shows typical characteristic pattern. The quantitative analysis carried out with five different MM simulations shows an increase in LV afterload and decrease in RV preload, which lead to decrease in LV stroke volume. Mean arterial pressure is not significantly changing, however, the pulse pressure reduces significantly that stimulates baroreflex activation in MM. This suggests that arterial baroreflex responds mainly to pulsatile pressure changes compared to mean pressure changes. The right heart hemodynamics are more affected than left heart dynamics in MM. The model results are well supported by the experimental data reported in literature. Therefore, the model can be used as a tool to investigate the CP system dynamics to various normal and abnormal conditions.