Pulmonary Hemodynamic Consequences of ECG-Synchronized Ventilation

Abstract

The pulmonary hemodynamic consequences of ECG-synchronized jet ventilation were studied in an acute closed chest swine model ( n = 11). Eight jet timing protocols were compared to conventional mechanical ventilation. Hearts were paced atrially at 120 beats per minute, and analog measurements of pulmonary arterial flow and pulmonary arterial, tracheal, pleural, left atrial, and femoral arterial pressure were digitized in real time at 200 Hz. Fourier analysis of pulmonary artery pressure and flow waveforms was employed to calculate mean and oscillatory right ventricular hydraulic power and pulmonary vascular input impedance. Measurements were taken at 0, 5, and 10 cm H 2O of positive end-expiratory pressure (PEEP) during conventional respiration and synchronized ventilation modes. No difference was found in mean pulmonary pressure and flow between conventional and synchronized ventilation at any level of PEEP, regardless of the timing of the jet pulse relative to the cardiac cycle. A significant difference in mean tracheal pressure between conventional and jet ventilation could be found only in the absence of PEEP (3.8 ± 0.5 vs 2.5 ± 0.3 mm Hg, P < 0.05). In the absence of PEEP, total hydraulic power was significantly less with respect to conventional ventilation when the jet pulse trailed the QRS complex by 90 and 135°. A significant decrease in the ratio of oscillatory-to-mean power versus conventional respiration was found when jet ventilation lagged the QRS by 135° (0.115 ± 0.015 vs 0.147 ± 0.013). These differences did not persist when PEEP was added. Moreover, no significant difference in hemodynamic variables was found when the various jet timing protocols were compared to each other. These data affirm the dominant role of mean tracheal pressure as the major variable modifying pulmonary hemodynamics but suggest that, at normal airway pressure, pulmonary hemodynamics may be modestly affected by synchronization of ventilation with the cardiac cycle.