Impact of inhaled gas compound on nitric dioxide release in a model of nitric oxide inhalation therapy (experimental study)

Background. Toxic effects of nitric dioxide (NO2) released under nitric oxide (NO) inhalation limit the application of nitric oxide high-dose therapy of clinical conditions accompanied by increased pulmonary vascular resistance. Objective. To identify the combinations of safe NO and O2 concentrations in inhaled gas compound for nitric dioxide release in a model of NO insufflation through the «Tianox» apparatus into respiratory circuit. Material and methods. The study was performed on an experimental model. There were 360 measurements of NO2 content in 72 various combinations of NO and O2. Results. NO2 release depended on NO and O2 content in gas mixture. Multivariate regression analysis confirmed this fact. NO2 concentration <2 ppm was recognized as a safe value. ROC-analysis confirmed predictive ability of NO and O2 regarding toxic NO2 concentrations. In case of inhalation therapy through the «Tianox» apparatus with any NO concentrations (10—80 ppm), O2 content in gas mixture within 21—30% was safe. NO concentration <50 ppm is safe at any O2 content in gas mixture (21—100%). Conclusion. There is a fundamentally new source of NO in the Tianox device (synthesis from atmospheric air). We obtained data on possible safe combinations of inhaled O2 and NO regarding NO2 release for effective clinical use of this device.