Respiratory Investigation Unit, Department of Medicine, Queen's University and Kingston Health Sciences Centre, Kingston General Hospital Campus, Kingston, Ontario, Canada.
Department of Chest Diseases, Faculty of Medicine, Alexandria University, Alexandria, Egypt.
Respirology. 2021 Aug;26(8):786-795. doi: 10.1111/resp.14045. Epub 2021 Apr 7.
The combination of both reduced resting diffusing capacity of the lung for carbon monoxide (DL ) and ventilatory efficiency (increased ventilatory requirement for CO clearance [V˙ /V˙CO ]) has been linked to exertional dyspnoea and exercise intolerance in chronic obstructive pulmonary disease (COPD) but the underlying mechanisms are poorly understood. The current study examined if low resting DL and higher exercise ventilatory requirements were associated with earlier critical dynamic mechanical constraints, dyspnoea and exercise limitation in patients with mild COPD.
In this retrospective analysis, we compared V˙ /V˙CO , dynamic inspiratory reserve volume (IRV), dyspnoea and exercise capacity in groups of patients with Global Initiative for Chronic Obstructive Lung Disease stage 1 COPD with (1) a resting DL at or greater than the lower limit of normal (≥LLN; Global Lung Function Initiative reference equations [n = 44]) or (2) below the <LLN (n = 33), and age- and sex-matched healthy controls (n = 81).
Spirometry and resting lung volumes were similar in the two COPD groups. During exercise, V˙ /V˙CO (nadir and slope) was consistently higher in the DL < LLN compared with the other groups (all p < 0.05). The DL < LLN group had lower IRV and greater dyspnoea intensity at standardized submaximal work rates and lower peak work rate and oxygen uptake than the other two groups (all p < 0.05).
Reduced exercise capacity in patients with DL < LLN was related to higher ventilatory requirements, a faster rate of decline in dynamic IRV and greater dyspnoea during exercise. These simple measurements should be considered for the clinical evaluation of unexplained exercise intolerance in individuals with ostensibly mild COPD.
肺一氧化碳弥散量（DL ）降低和通气效率（CO 清除的通气需求增加[V˙ / V˙CO ]）的结合与慢性阻塞性肺疾病（COPD）患者的运动性呼吸困难和运动不耐受有关，但潜在机制尚不清楚。本研究旨在探讨轻度 COPD 患者静息 DL 降低和运动时通气需求增加是否与更早出现的关键动态力学限制、呼吸困难和运动受限有关。
在这项回顾性分析中，我们比较了 V˙ / V˙CO 、动态吸气储备量（IRV）、呼吸困难和运动能力，将 Global Initiative for Chronic Obstructive Lung Disease 1 期 COPD 患者分为以下两组：（1）静息 DL 在或高于正常下限（≥LLN；Global Lung Function Initiative 参考方程[n=44]）；或（2）低于<LLN（n=33），并与年龄和性别匹配的健康对照组（n=81）进行比较。
两组 COPD 患者的肺量计和静息肺容积相似。在运动过程中，DL < LLN 组的 V˙ / V˙CO （最低点和斜率）始终高于其他两组（均 p<0.05）。与其他两组相比，DL < LLN 组在标准化亚最大工作率时的 IRV 较低，呼吸困难强度较大，而在峰值工作率和摄氧量时则较低（均 p<0.05）。
DL < LLN 患者的运动能力下降与更高的通气需求、IRV 动态下降更快以及运动时呼吸困难加重有关。这些简单的测量指标应考虑用于评估那些表面上患有轻度 COPD 但运动不耐受的患者的临床评估。
