Johansen B, Vale J R
Bull Eur Physiopathol Respir. 1984 Mar-Apr;20(2):151-6.
We examined the influence of "matching volume" on intrasubject variability of the descending limb of maximal expiratory flow-volume (MEFV) curves on air and helium-oxygen (He) in 18 healthy subjects and 28 patients with airflow limitation. Duplicate forced expirations were analysed according to four methods of alignment. With the first method, flows corresponding to identical percentiles of separate FVC (SEPVC) were compared. With the remaining three, we aligned curves at TLC, mid-vital capacity (VC50) and RV, respectively, for comparison of: a) flow at identical percentiles of the averaged FVC and b) expired volume at identical percentiles of the averaged peak flow. In healthy subjects, variability of flow at 50% and 75% of expired FVC (FEF50 and FEF75) did not change significantly with method, except that FEF75 on air varied more with method SEPVC than with VC50. In airflow limitation, FEF75 was significantly less reproducible when curves were matched at RV than at TLC, both on air and He. Over the latter part of expiration, an arbitrary index of variability of flow-defined volume also indicated that method RV gave the poorest precision in patients. We conclude that selection of matching volume does not influence the variability of MEFV-curves in health. In airflow limitation, however, TLC appears to be the most reliable volume for alignment.
我们研究了“匹配容积”对18名健康受试者和28名气流受限患者在空气和氦氧（He）环境下最大呼气流量-容积（MEFV）曲线下降支受试者内变异性的影响。根据四种校准方法对重复的用力呼气进行分析。第一种方法是比较对应于单独用力肺活量（SEPVC）相同百分位数的流量。对于其余三种方法，我们分别在肺总量（TLC）、肺活量中点（VC50）和残气量（RV）处校准曲线，以比较：a）平均用力肺活量相同百分位数处的流量，以及b）平均峰值流量相同百分位数处的呼出容积。在健康受试者中，呼出用力肺活量（FEF50和FEF75）50%和75%处的流量变异性随方法的变化不显著，只是空气中的FEF75在SEPVC方法下的变异性比在VC50方法下更大。在气流受限的情况下，无论是在空气还是氦气环境中，当在RV处校准曲线时，FEF75的可重复性明显低于在TLC处。在呼气后期，一个任意定义的流量-容积变异性指标也表明，RV方法在患者中精度最差。我们得出结论，匹配容积的选择不会影响健康状态下MEFV曲线的变异性。然而，在气流受限时，TLC似乎是最可靠的校准容积。
