Objective: This study examined whether ARDS patients in whom predefined ventilator settings fail to maintain oxygenation and CO2 removal can be safely transitioned to high-frequency oscillatory ventilation (HFOV), and whether HFOV use is efficacious.
Design and setting: Prospective observational study in the 14-bed intensive care unit of a university hospital.
Patients and participants: 42 patients with ARDS (APACHE II score 28 (IQR 24-37) and ventilation time prior HFOV 3.0 days (0.7-9.1).
Measurements and results: Gas exchange parameters and ventilator data were recorded before and during HFOV treatment (-12 h, -6 h, baseline, 10 min, 1 h, 6 h, 12 h, 24 h). Primary endpoints included: (a) PaO2/FIO2 ratio 24 h after start of HFOV treatment or the last point of measurement if HFOV ended within the first 24 h; (b) HFOV-related complications. Post hoc analysis assessed the relationship between outcome and the response to HFOV, and between outcome and time of mechanical ventilation prior to HFOV. At baseline the median PaO2/FIO2 ratio was 95 (IQR 62-129); after 24 h of HFOV the PaO2/FIO2 ratio had increased significantly to 165 (88-225); only one patient developed a unilateral pneumothorax. Of the 42 patients 18 (43%) had died by day 30. Subset analyses showed a significantly higher 30-day mortality rate in patients with at least 3 days of mechanical ventilation prior to HFOV (64%) and in patients without oxygenation improvement after 24 h on HFOV (71%).
Conclusions: HFOV is an effective and safe method to ventilate ARDS patients. Failure to improve oxygenation within 24 h of HFOV is associated with high mortality.