High-frequency oscillatory ventilation put on hold

By Eleanor McDermid, Senior medwireNews Reporter

Findings from two trials suggest that high-frequency oscillatory ventilation (HFOV) does not help, and may even harm patients with acute respiratory distress syndrome (ARDS).

The two randomized trials - Oscillation for Acute Respiratory Distress Syndrome Treated Early (OSCILLATE) and Oscillation in ARDS (OSCAR) - appear in The New England Journal of Medicine.

In an editorial accompanying the studies, Atul Malhotra (Brigham and Women's Hospital, Boston, Massachusetts, USA) and NEJM editor-in-chief Jeffrey Drazen stress that, for the time being, "clinicians should be cautious about applying HFOV routinely in patients with ARDS."

But they say that it may be the particular protocols used in the trials that are ineffective, rather than HFOV itself.

OSCILLATE was stopped early, after the enrollment of 548 of the planned 1200 patients, because of increased in-hospital mortality among those assigned to receive HFOV, at 47% versus 35% in patients receiving standard ventilation. Significantly more use of vasopressors was required in HFOV than control patients, at 78% versus 58% on the second day of ventilation, implying hemodynamic compromise caused by the increased airway pressures in the HFOV group.

In OSCILLATE - a multinational study led by Maureen Meade (McMaster University, Hamilton, Ontario, Canada) - the control group was ventilated with low tidal volumes and high positive end-expiratory pressure, to target lung recruitment. In OSCAR - a UK-based trial conducted by Duncan Young (John Radcliffe Hospital, Oxford) and team - patients in the control group were treated according to usual practice in the participating intensive care units. There was more variation of treatment in the control group of OSCAR than OSCILLATE, suggesting that physicians tailored treatment to individual patient needs.

HFOV did not increase mortality in the OSCAR trial, but neither did it improve patient outcomes. The 30-day mortality rates were 41.7% and 41.1% in the 398 patients assigned to HFOV and the 397 patients given standard ventilation, respectively. There was no increase in vasopressor use associated with HFOV; this disparity with OSCILLATE results could be due to the lower applied ventilatory pressures in OSCAR, say Malhotra and Drazen.

They observe that careful patient selection could be critical. "Among patients with homogeneous, recruitable lung, increasing mean airway pressure may well be beneficial; however, among patients with heterogeneous and nonrecruitable lung, increasing mean airway pressure may lead to overdistention of some lung regions without increased aeration of collapsed or flooded alveoli."

The editorialists say: "Further improvements in outcomes are likely to occur only through improved understanding of the heterogeneous ARDS phenotype and its underlying biologic characteristics."

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