Hemodynamic effects of synchronized high-frequency jet ventilation compared with low-frequency intermittent...

The purpose of this prospective study was to examine the effect on cardiac performance of selective increases in airway pressure at specific points of the cardiac cycle using synchronized high-frequency jet ventilation (sync-HFJV) delivered concomitantly with each single heart beat compared with controlled mechanical ventilation in 20 hemodynamically stable, deeply sedated patients immediately after coronary artery bypass graft.

Five 30-min sequential ventilation periods were used interspersing controlled mechanical ventilation with sync-HFJV twice to control for time and sequencing effects. Sync-HFJV was applied using a driving pressure, which generated a tidal volume resulting in gas exchanges close to those obtained on controlled mechanical ventilation and associated with the maximal mixed venous oxygen saturation. Hemodynamic variables including cardiac output, mixed venous oxygen saturation and vascular pressures were recorded at the end of each ventilation period.

The authors found that in 20 patients, hemodynamic changes induced by controlled mechanical ventilation and by sync-HFJV were similar. Cardiac index did not change (mean +/- SD for controlled mechanical ventilation: 2.6 +/- 0.7 l x min(-1) x m(-2); for sync-HFJV: 2.7 +/- 0.7 l x min(-1) x m(-2); P value not significant). This observation persisted after stratification according to baseline left-ventricular contractility, as estimated by ejection fraction.

The authors conclude that after coronary artery bypass graft, if gas-exchange values are maintained within normal range, sync-HFJV does not result in more favorable hemodynamic support than controlled mechanical ventilation. These findings contrast with the beneficial effects of sync-HFJV, resulting in marked hypocapnia, on cardiac performance observed in patients with terminal left-ventricular failure.