Distribution of ventilation and hemodynamic effects of different ventilatory patterns

OBJECTIVE: To compare the influence of cardiac-pulmonary function on clinical acute respiratory failure patients using Proportional assist ventilation (PAV), Pressure support ventilation (PSV) and intermittent positive pressure ventilation (IPPV). Here, we also describe some our experience with the clinical use of PAV. METHODS: Using the IPPV mode in ten acute respiratory failure patients, calculate Elastance (Ers) and Resistance (Rrs), then change to PSV, set inspiratory positive airway pressure (IPAP) according to IPPV, so that tidal volume (V(T)) is the same as that of IPPV. We then changed the mode into PAV and set the assist ratio according to PSV, so that V(T) and Ppeak were the same as that of PSV. Then we observed the changes of respiratory mechanics, blood gas levels and hemodynamics during ventilation. RESULTS: Compared with PSV and IPPV, peak pressure (Ppeak) of PAV was markedly lower while V(T) was similar; work of breathing of patient (WOBp), and work of breathing of ventilation (WOBv) were also lower; center vein pressure (CVP) and pulmonary capillary wedge pressure (PCWP) of PAV were markedly lower than that of IPPV while V(T) were similar. Compared with PSV, V(T), mean blood pressure (mBP) and cardiac output (CO) of PAV were higher. Mean pulmonary artery pressure (mPAP) and WOBp of PAV were lower while Ppeak was similar; the differences in WOBp were notable. CONCLUSIONS: For clinical acute respiratory failure patients, compared with PSV and IPPV, PAV has lower airway pressure, less WOBp and less influence on hemodynamics.