Hoyle ES, et al. - Researchers identified the difference among randomised controlled trials (RCTs) of inhaled nitric oxide (iNO) with respect to the definition of pulmonary hypertension (PH) and/or hypoxaemic respiratory failure used to choose patients for inclusion in the trial. For clinical and/or echocardiography criteria used to define PH/hypoxaemic respiratory failure, included studies were evaluated. In this review, 32 trials were involved of which 23 enrolled infants ≥ 34 weeks’ gestation. Markers of tricuspid regurgitation and extrapulmonary shunt were the most commonly used indices. The definition of PH used to select infants for the inclusion of iNO therapy in neonates in RCTs varies widely. They recommend reaching an international consensus on the parameters to be used and the thresholds that define disease severity.