Department of Respiratory Medicine, Hokkaido University , Sapporo , Japan.
J Appl Physiol (1985). 2018 Jul 1;125(1):183-189. doi: 10.1152/japplphysiol.01062.2017. Epub 2018 Apr 12.
The overlap between asthma and chronic obstructive pulmonary disease (COPD) has attracted the interest of pulmonary physicians; thus, measurement of carbon monoxide diffusion capacity (DLco) and/or transfer coefficients (Kco, DLco/V) may become valuable in clinical settings. How these parameters behave in chronic obstructive lung diseases is poorly understood. We predicted that Kco might more accurately reflect emphysematous changes in the lungs than DLco. We examined DLco and Kco in nonsmokers and smokers with asthma and investigated their relationships with forced expiratory volume in 1 s (%FEV) by group. We then selected nonsmokers (As-NS) and smokers with asthma (As-Sm) in both groups and those with COPD while controlling for the degree of airflow limitation across groups. Emphysema volumes [%lung attenuation volume (%LAV)] and percentage of cross-sectional area of small pulmonary vessels <5 mm (%CSA) were measured by computed tomography. In As-NS, %Kco was significantly higher when FEV% was reduced, but such a correlation was not seen in As-Sm. %Kco successfully differentiated among the three groups when airflow limitation levels were matched. However, %DLc, was significantly reduced only in patients with COPD. Both %LAV and %CSA were better correlated with %Kco than with %DLco. There was discordance between %DL and %Kco in As-Sm, which was not seen in As-NS. Overall, %Kco better reflects emphysematous changes in obstructive lung diseases than %DLco. NEW & NOTEWORTHY Despite differing behaviors of %Kco and %DLco in several diseases, the characteristics of these parameters have not been fully examined in smokers with asthma. Here, we demonstrated that %Kco is a more sensitive parameter of pathophysiology, better reflecting emphysematous changes in chronic obstructive lung diseases overall, compared with %DLco. Thus, more precise interpretations of %DLco and %Kco may provide clues for understanding the pathophysiology of obstructive lung diseases.
哮喘和慢性阻塞性肺疾病（COPD）之间的重叠引起了肺科医生的兴趣；因此，一氧化碳扩散能力（DLco）和/或转移系数（Kco，DLco/V）的测量在临床环境中可能变得有价值。这些参数在慢性阻塞性肺疾病中的表现知之甚少。我们预测 Kco 可能比 DLco 更能准确反映肺部气肿变化。我们检查了哮喘患者和非吸烟者的 DLco 和 Kco，并按组研究了它们与 1 秒用力呼气量（%FEV）的关系。然后，我们选择了两组中不吸烟的哮喘患者（As-NS）和吸烟的哮喘患者（As-Sm），以及那些在控制跨组气流限制程度的情况下患有 COPD 的患者。通过计算机断层扫描测量肺气肿体积[%肺衰减体积（%LAV）]和<5mm 小肺血管的横截面积百分比（%CSA）。在 As-NS 中，当 FEV%降低时，%Kco 显着升高，但在 As-Sm 中则没有。当气流限制水平相匹配时，%Kco 成功地区分了三组。然而，仅在 COPD 患者中 %DLc 显着降低。%LAV 和%CSA 与%Kco 的相关性均优于与%DLco 的相关性。在 As-Sm 中，%DL 和%Kco 之间存在不一致，而在 As-NS 中则没有。总体而言，与 %DLco 相比，%Kco 更好地反映了阻塞性肺疾病中的气肿变化。新内容和值得注意的内容尽管在几种疾病中%Kco 和%DLco 的行为不同，但在吸烟的哮喘患者中尚未充分检查这些参数的特征。在这里，我们证明与 %DLco 相比，%Kco 是一种更敏感的生理学参数，总体上更好地反映了慢性阻塞性肺疾病中的气肿变化。因此，更准确地解释%DLco 和%Kco 可能为理解阻塞性肺疾病的生理学提供线索。
