OBJECTIVE To assess the hemodynamic effects of high mean proximal airway pressures (Paw) during high-frequency oscillatory ventilation (HFOV) in non-neonatal pediatrics patients with severe respiratory failure. METHODS Prospective and retrospective study. METHODS Pediatric ICU in a university-affiliated hospital. METHODS 8 non-neonatal pediatric patients with severe respiratory failure ventilated with HFOV at our institution between July 1991 and February 1994. All patients had a pulmonary artery catheter. METHODS HFOV. RESULTS Higher Paw was required during HFOV to obtain adequate lung expansion during the first 24 h (median 20.9 cmH2O, range 16.9-30.0 cmH2O in CMV, versus median 30.0 cmH2O, range 21.0-33.0 cmH2O in HFOV, p = 0.008), resulting in improved oxygenation as evaluated by alveolar-arterial oxygen difference (median of 557.2 mmHg, range 360.4-607.8 mmHg in CMV, versus median of 410.5 mmHg, range 282.9-550.2 mmHg after 24 h of HFOV, p = 0.03). The only observed effect on the cardiovascular system was a decrease in heart rate (median of 162, range 129-178 in CMV, versus median of 142, range 104-195 after 24 h of HFOV, p = 0.03). Oxygen delivery, cardiac index, mean systemic arterial blood pressure, and pulmonary and systemic vascular resistances did not change significantly before and after HFOV in the patients as a group, although in one case a decrease in cardiac index and oxygen delivery was observed. CONCLUSIONS High-Paw HFOV must be used cautiously, but seems to have no discernible adverse effects on the cardiovascular system in most patients.