A human cardiopulmonary system model applied to the analysis of the Valsalva maneuver

Previous models combining the human cardiovascular and pulmonary systems ha ve not addressed their strong dynamic interaction. They are primarily cardi ovascular or pulmonary in their orientation and do not permit a full explor ation of how the combined cardiopulmonary system responds to large amplitud e forcing (e.g., by the Valsalva maneuver). To address this issue, we devel oped a new model that represents the important components of the cardiopulm onary system and their coupled interaction. Included in the model are descr iptions of atrial and ventricular mechanics, hemodynamics of the systemic a nd pulmonic circulations, baroreflex control of arterial pressure, airway a nd lung mechanics, and gas transport at the alveolar-capillary membrane. Pa rameters of this combined model were adjusted to fit nominal data, yielding accurate and realistic pressure, volume, and flow waveforms. With the same set of parameters, the nominal model predicted the hemodynamic responses t o the markedly increased intrathoracic (pleural) pressures during the Valsa lva maneuver. In summary, this model accurately represents the cardiopulmon ary system and can explain how the heart, lung, and autonomic tone interact during the Valsalva maneuver. It is likely that with further refinement it could describe various physiological states and help investigators to bett er understand the biophysics of cardiopulmonary disease.