Usefulness of APIMS for monitoring of nitrogen dioxides during NO inhaling therapy

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This project was conducted for measuring directly nitrogen dioxide during nitric oxide inhaling therapy. An Atmospheric Pressure Ionization Mass Spectrometry (APIMS) device was utilized in this study. First we improved the prototype of APIMS by changing the detector and the slit sizes between the first ionization room and the second ionization room. Then combinations of ionization gas and sample carrier gas were investigated. We found the good combination of SF6 in Ar for ionization gas and Ar for sample carrier gas for determining NO2. Calibration curve of NO2 in NO was obtained successfully, which was impossible by conventional chemiluminescence method detectors. Chemiluminescence analyzer and this system was applied for evaluation of the quality of absorber of impurity gases in pure gas. Molecular Sieve was the best absorber for removal of NO2 in NO.Moreover if SODALIME was used for absorber before entering into the patient, we noticed that the definite necessity of good filter (filter may produce any impurities) in order to remove small particulate matter or many kinds of impurities, because of APIMS showed many irregular peaks in the spectrogram. Then we applied nitrogen oxides in the concentration of less than 1 % of nitric oxide during NO inhaling therapy for model animals of pulmonary hypertension by monocrotaline. This animal model was not so sensitive for NO therapy itself that we could not see effects of varied concentration of nitrogen dioxides in NO for longer duration of therapy. Other methods for mimic pulmonary hypertension such as hypoxia should be tried and longer period observation of the conditions of animals up to several hours must be enabled.