Pulmonary vascular resistance is an important determinant of cardiac output after the Fontan procedure and is adversely affected by elevated mean airway pressure. High-frequency jet ventilation (HFJV) is an alternate form of mechanical ventilation which supports gas exchange at lower mean airway pressure. This study was performed to determine if HFJV could lower mean airway pressure and pulmonary vascular resistance and result in an increase in cardiac output after the Fontan procedure. We prospectively evaluated 13 patients ranging in age from 0.9 to 8.5 years (mean, 3.9 years) and in weight from 6.2 to 20.1 kg (mean, 13.9 kg). Right atrial, left atrial and pulmonary artery catheters were used to measure hemodynamic parameters. Cardiac index was measured by dye dilution technique, and pulmonary vascular resistance was calculated. The patients were stabilized on mechanical ventilation to achieve a PaCO2 = 30 +/- 5 mm Hg, and baseline hemodynamic and respiratory measurements were made. HFJV was begun at settings adjusted to achieve similar gas exchange. Respiratory and hemodynamic measurements were repeated after 30-60 minutes of HFJV. Mechanical ventilation was then resumed at baseline settings, and measurements were repeated 0.5-1 hour later. There was no significant change in gas exchange. HFJV resulted in a 50% reduction in mean airway pressure (9.2 +/- 0.2 cm H2O to 4.6 +/- 0.1 cm H2O, p less than 0.001), a 59% reduction in pulmonary vascular resistance (3.82 +/- 0.36 to 1.52 +/- 0.16 Woods units, p less than 0.001), and a 25% increase in cardiac index (2.32 +/- 0.12 l/min/m2 to 2.91 +/- 0.12 l/min/m2, p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)