Division of Respiratory Medicine, Department of Pediatrics, The Hospital for Sick Children, Toronto, ON, Canada.
Translational Medicine, The Research Institute, The Hospital for Sick Children, Toronto, ON, Canada.
PLoS One. 2017 Oct 11;12(10):e0185553. doi: 10.1371/journal.pone.0185553. eCollection 2017.
Nitrogen excreted from body tissues impacts the calculation of multiple breath nitrogen washout (MBWN2) outcomes. The aim of this study was to determine the effect of tissue N2 on MBWN2 outcomes in both healthy subjects and patients with CF and to assess whether it is possible to correct for tissue N2. The contribution of tissue N2 to MBWN2 outcomes was estimated by comparing MBWN2-derived functional residual capacity (FRCN2) to FRC measured by body plethysmography (FRCpleth) and by comparing MBW outcome measures derived from MBWN2 and sulfur hexafluoride MBW (MBWSF6). Compared to plethysmography and MBWSF6, MBWN2 overestimated FRC and lung clearance index (LCI). Application of mathematical tissue N2 corrections reduced FRCN2 values closer to FRCpleth in health and reduced LCIN2 in both health and CF, but did not explain all of the differences observed between N2-dependent and -independent techniques. Use of earlier washout cut-offs could reduce the influence of tissue N2. Applying tissue N2 corrections to LCIN2 measurements did not significantly affect the interpretation of treatment effects reported in a previously published interventional trial. While tissue N2 excretion likely has an impact on MBWN2 outcomes, better understanding of the nature of this phenomenon is required before routine correction can be implemented into current MBWN2 protocols.
从身体组织中排出的氮会影响多次呼吸氮冲洗（MBWN2）结果的计算。本研究的目的是确定组织 N2 对健康受试者和 CF 患者 MBWN2 结果的影响，并评估是否可以对组织 N2 进行校正。通过比较 MBWN2 衍生的功能残气量（FRCN2）与体描仪测量的功能残气量（FRCpleth）以及比较 MBWN2 和六氟化硫 MBW（MBWSF6）衍生的 MBW 结果测量值来估计组织 N2 对 MBWN2 结果的贡献。与体描仪和 MBWSF6 相比，MBWN2 高估了 FRC 和肺清除指数（LCI）。应用数学组织 N2 校正可降低 FRCN2 值，使其更接近 FRCpleth，在健康状况下降低 LCIN2，在健康和 CF 患者中均降低，但不能解释依赖和不依赖 N2 的技术之间观察到的所有差异。使用更早的冲洗截止值可以减少组织 N2 的影响。对 LCIN2 测量值应用组织 N2 校正并没有显著影响对先前发表的干预试验中报告的治疗效果的解释。虽然组织 N2 排泄可能对 MBWN2 结果有影响，但在将组织 N2 校正常规应用于当前 MBWN2 方案之前，需要更好地了解这种现象的性质。
