Cochrane G M, Prieto F, Clark T J
Thorax. 1977 Apr;32(2):171-6. doi: 10.1136/thx.32.2.171.
Analysis of airflow in the terminal portion of the maximal expiratory flow volume curve has been suggested as a useful test for the early diagnosis of chronic airways obstruction. Whether such an analysis can identify early disease, and whether any subsequent action can prevent the progress of chronic airways obstruction, is unknown and will require prospective studies. As a precursor of such a study we have tried to establish the intrasubject variability of those tests of forced expiration which may be used for screening. We therefore measured expiratory flow volume curves of five healthy males and five healthy females aged 20-30 years as this is an age-group in which early detection of airways obstruction may be of value. Flow volume curves were obtained on the same day of the week for six weeks, and on three separate days during this period we carried out three flow volume curves every hour from 9 am to 6 pm. The data were subjected to analysis of variance to determine the variability of each measurement. Data were collected from forced expired volume in one second (FEV1) forced vital capacity (FVC), maximum expiratory flow rates at 50% and 75% of expired vital capacity, and forced expiratory time (FET). The results showed no consistent pattern of diurnal variation over the working day. The variation in any subject for FEV1 and FVC over the study period was considerably less than variations detected in the maximal expiratory flow rates at 50% and 75% of the expired vital capacity and FET. Our results suggest that the intrasubject variation found in flow rates of the terminal portion of the maximal expiratory flow volume curve and forced expiratory time may limit the usefulness of these tests in detecting early airways obstruction. FEV1 and FVC are more reproducible tests and are therefore particularly suited for cross-sectional screening. The more sensitive maximal expiratory flow volume curve may, however, be more useful for long-term studies in individuals when the onset of disease is sought, or for short-term challenge studies requiring the most sensitive index of change in airway characteristics.
对最大呼气流量容积曲线终末部分的气流分析已被提议作为慢性气道阻塞早期诊断的一项有用检测。这种分析能否识别早期疾病，以及任何后续措施能否预防慢性气道阻塞的进展，目前尚不清楚，需要进行前瞻性研究。作为此类研究的前期准备，我们试图确定可用于筛查的用力呼气测试在受试者内的变异性。因此，我们测量了5名年龄在20至30岁之间的健康男性和5名健康女性的呼气流量容积曲线，因为这一年龄组中气道阻塞的早期检测可能具有价值。在六周内的同一周的同一天获取流量容积曲线，在此期间的三个不同日子里，从上午9点到下午6点，每小时进行三次流量容积曲线测量。对数据进行方差分析以确定每次测量的变异性。收集的数据包括一秒用力呼气容积（FEV1）、用力肺活量（FVC）、呼出肺活量50%和75%时的最大呼气流量率以及用力呼气时间（FET）。结果显示工作日期间没有一致的昼夜变化模式。在研究期间，任何受试者的FEV1和FVC的变化远小于在呼出肺活量50%和75%时的最大呼气流量率以及FET中检测到的变化。我们的结果表明，在最大呼气流量容积曲线终末部分的流速和用力呼气时间中发现的受试者内变异性可能会限制这些测试在检测早期气道阻塞方面的实用性。FEV1和FVC是更具可重复性的测试，因此特别适合横断面筛查。然而，更敏感的最大呼气流量容积曲线可能在寻找疾病发病的个体长期研究中，或在需要气道特征变化最敏感指标的短期激发研究中更有用。
