One-third of young adult patients in Australia and New Zealand may have received extracorporeal membrane oxygenation to treat respiratory failure associated with influenza A (H1N1), according to findings published recently.

There was a 21% mortality rate among these patients who had severe hypoxemia.

Researchers conducted an observational study of 68 patients with influenza-associated acute respiratory distress syndrome in Australia and New Zealand between June 1 and Aug. 31, 2009. All patients in the study group had received extracorporeal membrane oxygenation treatment. There were 61 cases of either confirmed 2009 influenza A(H1N1) (n=53) or influenza A which was not subtyped (n=8).

The aim of the study was to determine the incidence, clinical features, degree of pulmonary dysfunction, technical characteristics, duration of extracorporeal membrane oxygenation, complications and survival.

Prior to oxygenation treatment, the studied patients had severe respiratory failure despite advanced mechanical ventilatory support with a median Pao₂/fraction of inspired oxygen (FIo₂) ratio of 56 (48-63), positive end-expiratory pressure of 18 (15-20) cm H₂O and an acute lung injury score of 3.8 (3.5-4.0).

The median duration of oxygenation support was 10 (7-15) days.

Survival to ICU discharge was reported among 71% (n=48; 95% CI, 60%-82%) of patients. Of those 48 patients, 32 survived to hospital discharge and 16 remained as hospital inpatients.

There were 14 deaths, representing 21% of the study population (95% CI, 11%-30%). Six patients remained in the ICU; two of those patients remained on extracorporeal oxygenation treatment.