A randomised controlled trial and cost-effectiveness analysis of high-frequency oscillatory ventilation against conventional artificial ventilation for adults with acute respiratory distress syndrome. The OSCAR (OSCillation in ARDS) study

BACKGROUND: Patients with the acute respiratory distress syndrome (ARDS) require artificial ventilation but this treatment may produce secondary lung damage. High-frequency oscillatory ventilation (HFOV) may reduce this damage.

OBJECTIVES: To determine the clinical benefit and cost-effectiveness of HFOV in patients with ARDS compared with standard mechanical ventilation.

DESIGN: A parallel, randomised, unblinded clinical trial.

SETTING: UK intensive care units.

PARTICIPANTS: Mechanically ventilated patients with a partial pressure of oxygen in arterial blood/fractional concentration of inspired oxygen (P : F) ratio of 26.7 kPa (200 mmHg) or less and an expected duration of ventilation of at least 2 days at recruitment.

INTERVENTIONS: Treatment arm HFOV using a Novalung R100(®) ventilator (Metran Co. Ltd, Saitama, Japan) ventilator until the start of weaning. Control arm Conventional mechanical ventilation using the devices available in the participating centres.

MAIN OUTCOME MEASURES: The primary clinical outcome was all-cause mortality at 30 days after randomisation. The primary health economic outcome was the cost per quality-adjusted life-year (QALY) gained.

RESULTS: One hundred and sixty-six of 398 patients (41.7%) randomised to the HFOV group and 163 of 397 patients (41.1%) randomised to the conventional mechanical ventilation group died within 30 days of randomisation (p = 0.85), for an absolute difference of 0.6% [95% confidence interval (CI) -6.1% to 7.5%]. After adjustment for study centre, sex, Acute Physiology and Chronic Health Evaluation II score, and the initial P : F ratio, the odds ratio for survival in the conventional ventilation group was 1.03 (95% CI 0.75 to 1.40; p = 0.87 logistic regression). Survival analysis showed no difference in the probability of survival up to 12 months after randomisation. The average QALY at 1 year in the HFOV group was 0.302 compared to 0.246. This gives an incremental cost-effectiveness ratio (ICER) for the cost to society per QALY of £88,790 and an ICER for the cost to the NHS per QALY of £ 78,260.

CONCLUSIONS: The use of HFOV had no effect on 30-day mortality in adult patients undergoing mechanical ventilation for ARDS and no economic advantage. We suggest that further research into avoiding ventilator-induced lung injury should concentrate on ventilatory strategies other than HFOV.

TRIAL REGISTRATION: Current Controlled Trials ISRCTN10416500.