Nitrogen dioxide as a by-product of inhaled nitric monoxide therapy. Concentration in the inhaled gas mixture acceptable in clinical practice. A systematic review

Objective: The study aimed to review the literature data on the recommended maximum concentrations of nitrogen dioxide during inhaled therapy with nitric oxide and to propose a general list of recommendations on safe therapy with inhaled nitric oxide. Methods: The systematic review was performed according to the PRISMA 2020 criteria. A search was carried out in databases Russian Science Citation Index, MedLine, Cochrane Library using the keywords “nitrogen dioxide”, “limit concentration”, “annual limit value”, “inhaled nitric oxide”. Results: The review included 28 articles, 20 sources from regulatory authorities setting hygiene standards, and 2 instructions for devices. Conclusion: For short periods of NO inhalation not exceeding one hour, the maximum permissible concentration of NO2 in the inhaled gas mixture may be defined as 5 ppm. In cases of NO inhalation not exceeding 24 hours, the maximum permissible concentration of NO2 in the inhaled mixture should be considered as 2 ppm. If the duration of NO inhalation exceeds 24 hours, the permissible concentration of NO2 in the inhaled gas mixture should be limited to 1 ppm.