Evaluation of a delivery system and monitors for ventilator administration of nitric oxide

The aim of this study was to compare nitric oxide (NO) and nitrogen dioxide (NO2) measurements obtained by chemiluminescence and electrochemical monitors using a delivery system for ventilator administration of NO. The formation of NO2 in this system and the efficacy of a soda-lime absorber to scavenge NO2 from inspiratory gas were also evaluated. Various concentrations of NO without and with soda lime were administered to a model lung via a Servo ventilator 900C with controlled ventilation by setting mass-flow regulators to maintain desired concentrations of NO in 80% O2. Close correlations were found between NO concentrations, as well as NO2 concentrations, measured using electrochemical monitors (TM100; 1002, PACII) and a chemiluminescence monitor (CLA-510SS). Soda-lime removed NO2 almost completely during administration of 0-25 p.p.m. NO, although a high concentration of NO2 appeared in the breathing circuit without soda lime. Four hundred grams of soda lime continued to absorb NO2 effectively during long-term administration of inhaled NO.These findings suggest that electrochemical monitoring is accurate and clinically useful for measurements of NO and NO2 concentrations, and that low doses of inhaled NO can be administered safely and reliably with the NO delivery system using a soda-lime absorber and mass-flow regulators.