The safety of a nitric oxide inhalation system using a conventional infant respirator

Attention is becoming increasingly focused on inhalation of nitric oxide (NO) as a selective pulmonary vasodilator. Its metabolite nitrogen dioxide (NO2), however, is a toxic molecule. The purpose of the present study was to evaluate the safety of a NO inhalation system using a conventional infant respirator from the viewpoint of NO2 production. The NO inhalation system consisted of a standard neonatal ventilator, a neonatal circuit and a test lung. The NO concentration was increased from 0 up to 19 ppm. At each level of NO, the oxygen (O2) concentration was changed from 21 to 100%. The NO and NO2 concentrations were measured with a chemiluminescence analyzer using a molybdenum converter. The NO2 concentration was increased when either the O2 or the NO concentration was increased. The maximum concentration of NO2 was 0.10 +/- 0.02 ppm when the concentrations of NO and O2 were 19 ppm and 100% respectively. The NO inhalation system, using a conventional infant respirator, can be used safely when monitoring NO and NO2 concentrations.