A demand valve device decreases exhaust nitric oxide and nitrogen dioxide by nitric oxide inhalation with a nasal cannula in the human

Abstract

To improve patients' quality of life and decrease pollution risks to medical personnel, we tested the usefulness of a nitric oxide (NO) inhalation system consisting of a nasal cannula and a demand valve in an open circuit system. To estimate the content of NO entering the lung with the open system, concentrations of NO and nitrogen dioxide (NO2) were measured in a mechanical lung model, and then nitrocylhaemoglobin (NO- Hb), methaemoglobin (Met-Hb), and nitrite (NO2-) + nitrate (NO3-) concentrations in venous blood were measured in eight healthy subjects. Exhaust NO and NO2 in the open system were also observed in 14 healthy subjects. In the lung model, NO concentration delivered with the open system was approximately 1/11 of that in the gas tank. Increases in Met-Hb and NO2- + NO3- with the open system showed that the concentration of delivered NO was approximately 1/9 of that in the gas tank. The open system reduced exhaust NO to 1/10 in human subjects. These data suggest that this NO inhalation system delivers sufficient NO to spontaneously breathing patients. In addition, these findings indicate that there is little environmental toxicity associated with the open circuit system.