Department of Medicine, University of California, San Diego, California.
Department of Radiology, University of California, San Diego, California.
J Appl Physiol (1985). 2022 May 1;132(5):1290-1296. doi: 10.1152/japplphysiol.00511.2021. Epub 2022 Apr 21.
Multiple breath washout (MBW) testing is increasingly used as a physiological measurement in the clinic, due in part to the availability of commercial equipment and reference values for MBW indices. Commercial N washout devices are usually based on indirect measurement of N concentration (), by directly measuring either molar mass and O and CO, or molar mass and CO. We aim to elucidate the role of two potential pitfalls associated with N-MBW testing that could override its physiological content: indirect N measurement and blood-solubility of N. We performed MBW in 12 healthy adult subjects using a commercial device (MBW) with simultaneous direct gas concentration measurements by mass spectrometry (MBW) and compared between MBW and MBW. We also measured argon concentration during the same washouts to verify the maximal effect gas solubility can have on N-based functional residual capacity (FRC) and lung clearance index (LCI). Continuous N concentration traces were very similar for MBW and MBW, resulting in comparable breath-by-breath washout plots of expired concentration and in no significant differences in FRC, LCI, S, and S between the two methods. Argon washouts were slightly slower than N washouts, as expected for a less diffusive and more soluble gas. Finally, comparison between LCI and LCI indicates that the maximum impact from blood-tissue represents less than half a LCI unit in normal subjects. In conclusion, we have demonstrated by direct measurement of N and twice as soluble argon, that indirect N measurement can be safely used as a meaningful physiological measurement. The physiological content of N multibreath washout testing has been questioned due to N indirect measurement accuracy and N blood solubility. With direct measurement of N and twice as soluble argon, we show that these effects are largely outweighed by ease of use.
多次呼吸冲洗（MBW）测试由于商业设备和 MBW 指数参考值的可用性，在临床中越来越多地被用作生理测量。商业 N 冲洗设备通常基于 N 浓度的间接测量（），通过直接测量摩尔质量和 O 和 CO，或摩尔质量和 CO。我们旨在阐明与 N-MBW 测试相关的两个潜在陷阱的作用，这些陷阱可能会推翻其生理内容：间接 N 测量和 N 的血液溶解度。我们使用商业设备（MBW）在 12 名健康成年受试者中进行 MBW 测试，同时通过质谱法（MBW）进行直接气体浓度测量，并比较了 MBW 和 MBW 之间的差异。我们还在相同的冲洗过程中测量了氩气浓度，以验证气体溶解度对基于 N 的功能残气量（FRC）和肺清除指数（LCI）的最大影响。MBW 和 MBW 的连续 N 浓度轨迹非常相似，导致呼出浓度的呼吸-by-呼吸冲洗图相似，两种方法之间在 FRC、LCI、S 和 S 方面没有显着差异。氩气冲洗比 N 冲洗稍慢，这是由于扩散性较小且更易溶解的气体所致。最后，LCI 和 LCI 之间的比较表明，在正常受试者中，来自血液组织的最大影响代表不到半个 LCI 单位。总之，我们通过直接测量 N 和两倍可溶性的氩气，证明间接 N 测量可以安全地用作有意义的生理测量。由于 N 间接测量精度和 N 血液溶解度，N 多呼吸冲洗测试的生理内容受到质疑。通过直接测量 N 和两倍可溶性氩气，我们表明这些影响在很大程度上被易用性所抵消。
