Hemodynamic effects of synchronized high-frequency jet ventilation compared with low-frequency intermittent positive-pressure ventilation after myocardial revascularization

Background: The purpose of this prospective study was to examine the effect on cardiac performance of selective increases in airway pressure at specif ic points of the cardiac cycle using synchronized high-frequency jet ventil ation (sync-HFJV) delivered concomitantly with each single heart beat compa red with controlled mechanical ventilation in 20 hemodynamically stable, de eply sedated patients immediately after coronary artery bypass graft. Methods: 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, wh ich generated a tidal volume resulting in gas exchanges close to those obta ined on controlled mechanical ventilation and associated with the maximal m ixed venous oxygen saturation, Hemodynamic variables including cardiac outp ut, mixed venous oxygen saturation and vascular pressures were recorded at the end of each ventilation period. Results: The authors found that in 20 patients, hemodynamic changes induced by controlled mechanical ventilation and by sync-HFJV were similar. Cardia c index did not change (mean +/- SD for controlled mechanical ventilation: 2.6 +/- 0.7 l . min(-1) . m(-2); for sync-HFJV: 2.7 +/- 0.7 l . min(-1) . m (-2); P value not significant). This observation persisted after stratifica tion according to baseline left-ventricular contractility, as estimated by ejection fraction. Conclusions: The authors conclude that after coronary artery bypass graft, if gas-exchange values are maintained within normal range, sync-HFJV does n ot result in more favorable hemodynamic support than controlled mechanical ventilation. These findings contrast with the beneficial effects of sync-HF JV, resulting in marked hypocapnia, on cardiac performance observed in pati ents with terminal left-ventricular failure.