Cardiovascular variables changes during positive pressure ventilation - Computer simulation

Positive pressure ventilation used nowadays extensively to preserve life, to assist inefficient spontaneous breathing or during any kind of surgery is known to have an adverse effect on cardiovascular system. Usually positive pressure in alveoli diminishes lung perfusion, venous return and cardiac output in turn. This non-physiological, always non-negative alveolar pressure during the respiratory cycle is transferred into thoracic space. A lot of modes of artificial ventilation have been developed recently, which differ significantly as far as pressure, flow and cycling patterns are concerned. But experimental and clinical investigations proved that hemodynamic effects of mechanical ventilation are mainly dependent on a single variable - mean value of thoracic pressure generated during ventilatory cycle. So, no matter what technique is used to replace patient's breathing, changes in mean thoracic pressure will decide about the net effect of ventilatory support on cardiovascular system. The aim of the study was to assess the influence of positive thoracic pressures on main cardiovascular variables during simulation of active pulmonary vasoconstriction and without this phenomenon.