经麻醉机笑气通路吸入低浓度一氧化氮的可行性

Safety of delivering nitric oxide through nitrous oxide path in anesthesia machine

为了探讨术中将一氧化氮气体经麻醉机笑气通路安全地引入呼吸环路的可行性,选择SIEMENS Ventilator 710及NARKOMED 2B麻醉机分别与模拟肺相连组成环路。在新鲜氧气流量分别为2、3、4、5和6L/min。NO浓度分别为10、20、40、60和80ppm条件下,对环路内一氧化氮和二氧化氮浓度进行观察。结果表明:经麻醉机笑气通路引入800ppm一氧化氮,试验条件下环路内二氧化氮浓度均低于5.0ppm。碱石灰对一氧化氮和二氧化氮均有明显吸收作用。一氧化氮浓度、通气量和吸气支长度对呼吸环路内二氧化氮生成均有显著影响。我们认为在严密监测下,术中将高浓度一氧化氮气体经麻醉机笑气通路引入呼吸环路是安全可行的。

To evaluate the feasibility of delivering NO through N_2O path in anesthesia machine,NO at 800 ppm was delivered through nitrous oxide path in anesthesia machine SIEMENS Ventilator 710 or NARKOMED 2B,to ventilate a test lung. The minute volume of ventilation (MV) was set from 2 to 6L/min, and NO concentration from 10 to 80 ppm. NO and NO_2 concentrations were measured by hemiluminescence and electro-chemical fuel cell technique. SIEMENS Ventilator 710:Non-rebreathing model,its inspiratory limb was prolonged to 7 meters,the NO level was adjusted at 80ppm before passing through soda lime, NO and NO_2 samples were taken before absorber,after absorber, 1, 2,4 and 6 meter site in inspiratory limb. NARKOMED 2B:Oxygen flows were at the rates epual to the MV mentioned above, NO concentration was at 10,20,40,60 and 80 ppm,the inspiratory gas mixture was sampled immediately passing through absorber, NO_2 levels were less than 5.0ppm in all conditions listed above. With SIEMENS Ventilator 710, the highest level of NO_2 was 3.45 ppm before absorber and 2.43 ppm after absorber,with NARKOMED 2B,that was 3.6 ppm. As MV increased,NO_2 level before absorber decreased (P<0.01), NO level increased and NO_2 level varied after absorber (P<0.01); NO_2 level increased and NO level decreased (P<0.01) in inspiratory limb with the limb prolonged;NO_2 and NO levels in inspiratory limb were significantly affected by MV (P<0.01). With NARKOMED 2B,inspired oxygen fraction decreased with NO level increasing; NO_2 level was positively correlated with NO level (P<0.01). The data demonstrate that NO_2 level is kept at less than 5.0 ppm during the delivery of NO, soda lime absorber can scavenge NO_2 partly from inspiratory gas mixture and the monitoring port should be placed as closer to the patient as possible.