Therapy High-Frequency Oscillation for Acute Respiratory Distress Syndrome
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Summary
Posted By:	Elizabeth Sweetman & Gordon Doig
E-Mail:	esweetman@med.usyd.edu.au
Posted Date:	27.02.2013
Title:	High-Frequency Oscillation for Acute Respiratory Distress Syndrome
Authors:	Young D, Lamb SE, Shah S, Mackenzie I, Tunnicliffe W, Lall R, Rowan K, Cuthbertson BH; the OSCAR Study Group.
Reference:	N Engl J Med. 2013 Jan 22
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Abstract:	Background Patients with the acute respiratory distress syndrome (ARDS) require mechanical ventilation to maintain arterial oxygenation, but this treatment may produce secondary lung injury. High-frequency oscillatory ventilation (HFOV) may reduce this secondary damage. Methods In a multicenter study, we randomly assigned adults requiring mechanical ventilation for ARDS to undergo either HFOV with a Novalung R100 ventilator (Metran) or usual ventilatory care. All the patients had a ratio of the partial pressure of arterial oxygen (PaO(2)) to the fraction of inspired oxygen (FiO(2)) of 200 mm Hg (26.7 kPa) or less and an expected duration of ventilation of at least 2 days. The primary outcome was all-cause mortality 30 days after randomization. Results There was no significant between-group difference in the primary outcome, which occurred in 166 of 398 patients (41.7%) in the HFOV group and 163 of 397 patients (41.1%) in the conventional-ventilation group (P=0.85 by the chi-square test). After adjustment for study center, sex, score on the Acute Physiology and Chronic Health Evaluation (APACHE) II, and the initial PaO(2):FiO(2) ratio, the odds ratio for survival in the conventional-ventilation group was 1.03 (95% confidence interval, 0.75 to 1.40; P=0.87 by logistic regression). Conclusions The use of HFOV had no significant effect on 30-day mortality in patients undergoing mechanical ventilation for ARDS. (Funded by the National Institute for Health Research Health Technology Assessment Programme; OSCAR Current Controlled Trials number, ISRCTN10416500 .).
Are the Results Valid?
1. Was the assignment of patients to treatments randomized? ( Was allocation concealment maintained?)
	Yes. Patients were randomised to either HFOV or conventional mechanical ventilation through an independent telephone randomisation system. Details of HFOV protocol and conventional MV stratergy Study Treatments, p 2-3.
2. Were all patients who entered the trial properly accounted for and attributed at its conclusion?
2a. Was followup complete?
	Yes. All patients who were randomised into the trial were accounted for and followed up (Figure 1, Page 4).
2b. Were patients analyzed in the groups to which they were randomized?
	Yes patients were analysed in the groups to which they were randomised.
3. Were patients, health workers, and study personnel blind to treatment?
	No blinding of patients, health care workers or study personnel to study groups was documented by the authors in this paper.
4. Were the groups similar at the start of the trial?
	Yes the study groups were similiar at the start of the trial.
5. Aside from the experimental intervention, were the groups treated equally?
	Neuromuscular blocking agents were used more in the HFOV group 2.0 days vs Conventional ventilation group 2.5 days, P = 0.02.
What are the Results?
1. How large was the treatment effect?
	Primary Outcome: Vital status at 30 days: No difference between groups HFOV Group 41.7% vs 41.1% Conventional Ventilation Group, P = 0.85
2. How precise was the estimate of the treatment effect?
	Primary Outcome 95% Confidence Interval -6.1 to 7.5)
Will the Results Help Me In Caring For My Patients?
1. Can the results be applied to my patient care?
	Yes. This study provides a comparision of early switch to HFOV against a background of conventional ventilation, which may include an 'encouraged' attempt to adhere to the ARDs NET Low Tidal Volume Ventilation protocol.
2. Were all clinically important outcomes considered?
	Given that mortality did not differ between groups, it is important to note that quality of life will be reported at long-term follow-up. It is possible that functional recovery rates may differ between groups.
3. Are the likely treatment benefits worth the potential harms and costs?
	In the context of a conventional ventilation comparison group, we are awaiting longer term follow-up.
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