The lung clearance index (LCI) measured by multiple-breath washout (MBW) is defined as the number of lung volume turnovers needed to reduce the concentration of a blood-insoluble tracer gas by a factor of 40 during tidal breathing [1]. Over the past two decades, the MBW test has proven to be particularly useful in cystic fibrosis, and studies [2, 3] have demonstrated its superior sensitivity to that of forced expiratory volume in 1 s (FEV1). The ideal tracer gas for the LCI test is so insoluble in blood that any gas exchange effects are insignificant, and it can be measured in concentrations low enough that the tracer itself does not affect the physical properties of the respired air or gas mix. Historically, SF6 is the tracer gas that is most often used in the implementation of the MBW test [1]. However, it has been suggested that the LCI can instead be derived from the washout of nitrogen resident in the lungs using 100% oxygen, and this approach is being applied in a number of ongoing clinical trials. Nitrogen diffuses from blood into lung during nitrogen washout which can affect multiple breath washout results http://ow.ly/9dcy30dOuwZ

中文翻译：

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用 100% 氧气多次呼吸冲洗过程中的氮气反向扩散

通过多次呼吸冲洗 (MBW) 测量的肺清除指数 (LCI) 定义为在潮式呼吸期间将血液不溶性示踪气体浓度降低 40 倍所需的肺容积周转次数 [1]。在过去的 20 年中，MBW 测试已被证明在囊性纤维化中特别有用，并且研究 [2, 3] 已证明其对 1 秒内用力呼气量 (FEV1) 的敏感性更高。用于 LCI 测试的理想示踪气体在血液中非常难溶，因此任何气体交换效应都可以忽略不计，并且可以在足够低的浓度下进行测量，以至于示踪剂本身不会影响呼吸空气或气体混合物的物理特性。历史上，SF6 是最常用于实施 MBW 测试的示踪气体 [1]。然而，有人建议，LCI 可以从使用 100% 氧气冲洗肺中的氮来获得，并且这种方法正在许多正在进行的临床试验中得到应用。在氮冲洗过程中，氮会从血液扩散到肺部，这会影响多次呼气冲洗结果 http://ow.ly/9dcy30dOuwZ