In this week's BMJ, Adhikari and colleagues report a systematic review of the impact of inhaled nitric oxide on physiological outcomes, morbidity, and mortality in people with acute respiratory distress syndrome.1 They found that nitric oxide resulted in a limited improvement in oxygenation but did not reduce mortality (risk ratio 1.10; 95% confidence interval 0.94 to 1.30), the duration of ventilation, or the number of days free of ventilation.

Acute respiratory distress syndrome is an important public health problem. It is a catastrophic form of acute respiratory failure that arises after pulmonary (for example, pneumonia or aspiration of gastric contents) or extrapulmonary (for example, sepsis or polytrauma) insults. Not only does it have an incidence as high as 64 cases per 100 000 people per year,2 but it has a high mortality rate (30-60% in unselected populations) and risk of subsequent morbidity in survivors.3

The many cellular and molecular actions of nitric oxide (the 1992 “molecule …