Tamhane R M, Johnson R L, Hsia C C
Department of Medicine, University of Texas Southwestern Medical Center, Dallas, TX 75390-9034, USA.
Chest. 2001 Dec;120(6):1850-6. doi: 10.1378/chest.120.6.1850.
To validate lung diffusing capacity for nitric oxide (DLNO) as an index of conductance of the alveolar-capillary membrane during exercise, we compared DLNO to lung diffusing capacity for carbon monoxide (DLCO) and pulmonary membrane diffusing capacity for carbon monoxide (DMCO), and compared pulmonary capillary blood volume (Vc) calculated by two methods.
The study was performed at a university medical center involving 12 nonsmoking healthy volunteers (age range, 23 to 79 years). DLCO, DLNO, cardiac output (c), and lung volume were measured simultaneously at rest and during graded ergometer exercise by a rebreathing technique. Pulmonary membrane diffusing capacity and Vc were compared by (1) the classic technique of Roughton and Forster from DLCO measured at two alveolar oxygen tension (PAO(2)) levels, and (2) from DLNO and DLCO assuming negligible erythrocyte resistance to nitric oxide (NO) uptake, ie, DLNO approximately equal to pulmonary membrane diffusing capacity for nitric oxide.
In all subjects, DLNO increased linearly from rest to exercise; age, c, and lung volume were the major determinants of DLNO by stepwise regression analysis. The DLNO/DLCO ratio averaged 3.98 +/- 0.38 (+/- SD) and the DLNO/DMCO ratio averaged 2.49 +/- 0.28 irrespective of exercise intensity. Changing PAO(2) did not alter DLNO. Brief exposure to 40 ppm of inhaled NO during 16 s of rebreathing did not alter either DLCO or c. Estimates of pulmonary membrane diffusing capacity and Vc by the two methods showed a strong correlation.
Results support DLNO as a direct measure of pulmonary membrane diffusing capacity, allowing the estimation of Vc in a single rebreathing maneuver during exercise. The DLNO-DLCO rebreathing technique can be applied clinically in the investigation of pulmonary microvascular regulation.
为验证一氧化氮肺扩散容量（DLNO）作为运动期间肺泡 - 毛细血管膜传导性指标的有效性，我们将DLNO与一氧化碳肺扩散容量（DLCO）和一氧化碳肺膜扩散容量（DMCO）进行了比较，并比较了用两种方法计算的肺毛细血管血容量（Vc）。
该研究在一所大学医学中心进行，涉及12名不吸烟的健康志愿者（年龄范围为23至79岁）。通过重复呼吸技术在静息状态和分级测力计运动期间同时测量DLCO、DLNO、心输出量（c）和肺容积。通过以下两种方法比较肺膜扩散容量和Vc：（1）根据在两个肺泡氧分压（PAO₂）水平下测量的DLCO，采用Roughton和Forster的经典技术；（2）根据DLNO和DLCO，假设红细胞对一氧化氮（NO）摄取的阻力可忽略不计，即DLNO近似等于一氧化氮肺膜扩散容量。
在所有受试者中，DLNO从静息状态到运动时呈线性增加；通过逐步回归分析，年龄、c和肺容积是DLNO的主要决定因素。无论运动强度如何，DLNO/DLCO比值平均为3.98±0.38（±标准差），DLNO/DMCO比值平均为2.49±0.28。改变PAO₂不会改变DLNO。在16秒的重复呼吸过程中短暂暴露于40 ppm吸入的NO，既不会改变DLCO也不会改变c。两种方法对肺膜扩散容量和Vc的估计显示出很强的相关性。
结果支持DLNO作为肺膜扩散容量的直接测量指标，可在运动期间的单次重复呼吸操作中估计Vc。DLNO - DLCO重复呼吸技术可临床应用于肺微血管调节的研究。
