Kaminsky David A, Whitman Todd, Callas Peter W
Pulmonary Disease and Critical Care Medicine, University of Vermont College of Medicine, Given D-302, 89 Beaumont Avenue, Burlington, VT 05405, USA.
Respir Med. 2007 May;101(5):989-94. doi: 10.1016/j.rmed.2006.09.003. Epub 2006 Oct 18.
The diffusing capacity of the lung is usually reported as both the diffusing capacity (DLCO) and the diffusing capacity divided by the alveolar volume (DLCO/VA). However, it is unclear which measure to use when interpreting pulmonary gas exchange. We therefore conducted this study to determine whether the DLCO or the DLCO/VA is a better predictor of oxygen desaturation with exercise.
We retrospectively analyzed the pulmonary function records of all patients who had measurement of their diffusing capacity and 6-min walk oximetry in our university pulmonary function laboratory over a 2-year period.
There were data available on 97 patients, most of who had interstitial lung disease and/or lung volume restriction. The median DLCO was 51% predicted and the median DLCO/VA was 64% predicted. The prevalence of exercise desaturation was 43%. The overall sensitivity and specificity as determined by the area under the receiver operator characteristic (ROC) curve was higher for DLCO than DLCO/VA, with an optimal cut-off of normal of 55% predicted. The positive predictive values were equally low for both measures, ranging from 50% to 70%. After adjustment for VA, there were no differences between the ROC curves or predictive values for DLCO and DLCO/VA.
After adjusting for VA, neither the DLCO nor the DLCO/VA was better at predicting oxygen desaturation with exercise. The optimal cut-off of normal was 55% predicted.
肺弥散功能通常以弥散量（DLCO）和弥散量除以肺泡容积（DLCO/VA）来表示。然而，在解释肺气体交换时，尚不清楚应使用哪种测量方法。因此，我们进行了这项研究，以确定DLCO还是DLCO/VA能更好地预测运动时的氧饱和度下降。
我们回顾性分析了在两年期间内，在我校肺功能实验室进行弥散功能测量和6分钟步行血氧饱和度测定的所有患者的肺功能记录。
共有97例患者的数据，其中大多数患有间质性肺疾病和/或肺容积受限。DLCO的中位数为预测值的51%，DLCO/VA的中位数为预测值的64%。运动性氧饱和度下降的患病率为43%。由受试者工作特征（ROC）曲线下面积确定的总体敏感性和特异性，DLCO高于DLCO/VA，正常的最佳截断值为预测值的55%。两种测量方法的阳性预测值同样较低，范围为50%至70%。在对VA进行校正后，DLCO和DLCO/VA的ROC曲线或预测值之间没有差异。
在对VA进行校正后，DLCO和DLCO/VA在预测运动时的氧饱和度下降方面都没有更好的表现。正常的最佳截断值为预测值的55%。
