Objective: To assess the feasibility of using respiratory frequencies up to 15 Hz during high-frequency oscillatory ventilation (HFO) of adults with acute respiratory distress syndrome (ARDS).
Design: Observational study.
Setting: Medical intensive care unit at a tertiary care university hospital.
Patients: Thirty adult patients receiving HFO at the discretion of their physicians for management of severe ARDS.
Interventions: Clinical management algorithm for HFO that minimized delivered tidal volumes by encouraging the use of the highest frequency that allowed acceptable clearance of carbon dioxide. This contrasts with the typical use of HFO in adults, in which frequencies generally do not exceed 6 Hz.
Measurements and main results: Patients were 42 +/- 15 yrs old, weighed 83 +/- 25 kg, and had failed conventional lung-protective ventilation due to refractory hypoxia or respiratory acidosis and high plateau airway pressures. During HFO, 25 of 30 patients maintained acceptable gas exchange at frequencies > 6 Hz; 12 reached maximal frequencies of > or = 10 Hz. Among patients whose maximal frequencies exceeded 6 Hz, mean maximal frequency was 9.9 +/- 2.1 Hz, at a mean oscillation pressure amplitude of 81 +/- 11 cm H2O. At those settings, blood gases were pH 7.31 +/- 0.06, PaCO2 was 58 +/- 21 mm Hg, and PaO2 was 82 +/- 33 mm Hg. Survival to hospital discharge among this severely ill cohort was 37%.
Conclusions: Most adults can maintain adequate gas exchange using HFO frequencies well above 5-6 Hz. Use of higher frequencies should minimize tidal volume and we speculate might thereby reduce ventilator-associated lung injury.