The experimental research on inhaled nitric oxide and helium oxygen mixture in the asthma tic dog

Objective: To investigate the effect of Nitric Oxide （NO） as a bronchodilator on releasing bronchoconstriction and improving pulmonary gas exchange through the experimental research, and investigate the effect of inhaling NO and Helium Oxygen mixture （Heliox） simultaneously on asthmatic dogs. Methods: 12 male mangles were included in this study. The bronchoconstriction was induced by intratracheal infusion of methacholine. Then the inspiratory resistance （Ri）, the pulmonary artery pressure （Ppa）, the effective respiratory system compliance （Ceff） and pulmonary gas exchange were monitored during inhaling 100 ppm NO or inhaling Heliox and NO simultaneously. Results: The RI and Ppa increased significantly after bronchospasm, whereas Ceff and PaO₂ decreased. At the same time the pulmonary shunt （Qs/Qt） and PaCO₂ were increased. Inhaling 100 ppm NO decreased Ri and Ppa, but did not improved Ceff, PaO₂, PaCO₂ and Qs/Qt. However inhaling NO and Heliox simultaneously decreased more Ri and Ppa, and improved more pulmonary gas exchange compared with inhaling NO. Conclusion: Inhalation of high concentration of NO can inverse partly the bronchospasm induced by methacholine in the dog, but not improve the gas exchange. However, inhaling Heliox not only decreases the resistance of airways, but also improves the gas exchange in the lung.