Respiratory Investigation Unit, Department of Medicine, Queen's University, and Kingston Health Sciences Centre, Kingston, Ontario, Canada.
Department of Chest Diseases, Faculty of Medicine, Alexandria University, Alexandria, Egypt.
COPD. 2021 Oct;18(5):501-510. doi: 10.1080/15412555.2021.1932782. Epub 2021 Sep 8.
Patients with mild chronic obstructive pulmonary disease (COPD) and lower resting diffusing capacity for carbon monoxide (DL) often report troublesome dyspnea during exercise although the mechanisms are not clear. We postulated that in such individuals, exertional dyspnea is linked to relatively high inspiratory neural drive (IND) due, in part, to the effects of reduced ventilatory efficiency. This cross-sectional study included 28 patients with GOLD I COPD stratified into two groups with ( = 15) and without ( = 13) DL less than the lower limit of normal (<LLN; Global Lung Function Initiative criteria) and 16 healthy controls. We compared dyspnea (Borg scale), IND (by diaphragm electromyography), ventilatory equivalent for CO (/CO), and respiratory mechanics during incremental cycle exercise in the three groups. Spirometry and resting lung volumes were similar between COPD groups. During exercise, dyspnea, IND and /CO were higher at equivalent work rates (WR) in the DL<LLN group compared with the other two groups (all < 0.05). In patients with DL<LLN, severe respiratory mechanical constraints, indicated by end-inspiratory lung volume of approximately 90% of total lung capacity, occurred at a lower WR than the other two groups ( < 0.05). The dyspnea/IND relationship was similar across groups; therefore, the increased dyspnea at a standardized WR in the low DL<LLN group reflected the higher corresponding IND. Higher dyspnea ratings in patients with mild COPD and DL<LLN were associated with higher IND and /CO at a given work rate. Higher ventilatory requirements in the DL<LLN group accelerated dynamic mechanical abnormalities earlier in exercise, further increasing IND and dyspnea.
患有轻度慢性阻塞性肺疾病（COPD）和较低静息一氧化碳弥散量（DL）的患者在运动时经常会感到呼吸困难，尽管其机制尚不清楚。我们推测，在这些患者中，运动性呼吸困难与相对较高的吸气神经驱动（IND）有关，部分原因是通气效率降低的影响。这项横断面研究纳入了 28 名 GOLD I COPD 患者，分为两组：一组（ = 15）DL 低于正常值下限（<LLN；全球肺功能倡议标准），另一组（ = 13）DL 正常。我们比较了三组患者在递增循环运动期间的呼吸困难（Borg 量表）、IND（膈肌肌电图）、CO 通气当量（/CO）和呼吸力学。COPD 组的肺活量和静息肺容积相似。在运动过程中，DL<LLN 组在等效工作率（WR）时呼吸困难、IND 和 /CO 更高（均 < 0.05）。在 DL<LLN 患者中，严重的呼吸力学限制，表现为吸气末肺容积约为肺总量的 90%，在比其他两组更低的 WR 时出现（ < 0.05）。DL<LLN 患者的呼吸困难/IND 关系与其他两组相似；因此，在标准化 WR 下，低 DL<LLN 组的呼吸困难增加反映了相应的 IND 更高。在轻度 COPD 和 DL<LLN 患者中，更高的呼吸困难评分与给定工作率下更高的 IND 和 /CO 相关。DL<LLN 组更高的通气需求在运动早期加速了动态力学异常，进一步增加了 IND 和呼吸困难。
