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Original Research: COPD |

Efficiency of Neural Drive During Exercise in Patients With COPD and Healthy Subjects

Yin-Yin Qin, MD; Joerg Steier, PhD; Caroline Jolley, MD; John Moxham, MD; Nan-Shan Zhong, MD; Yuan-Ming Luo, PhD
Author and Funding Information

From the State Key Laboratory of Respiratory Disease (Drs Qin, Zhong, and Luo), Guangzhou Medical College, Guangzhou, China; and the Respiratory Muscle Laboratory (Drs Steier, Jolley, and Moxham), King’s College Hospital, London, England.

Correspondence to: Y. M. Luo, PhD, State Key Laboratory of Respiratory Disease, 151Yanjiang Rd, Guangzhou 510120, China; e-mail: ym3698@yahoo.com.cn


Funding/Support: This study was supported by the Chinese Natural Scientific Foundation [Grant 30770937] and International Collaboration Grant supported by Chinese Ministry of Science and Technology [Grant 2005DFA30910].

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (http://www.chestpubs.org/site/misc/reprints.xhtml).


© 2010 American College of Chest Physicians


Chest. 2010;138(6):1309-1315. doi:10.1378/chest.09-2824
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Background:  It is unknown whether efficiency of neural drive as expressed by a ratio of ventilation to the diaphragm electromyogram (EMGdi) in patients with COPD differs from that of healthy subjects during exercise and whether maximal neural drive is exhibited at the point of exercise termination.

Methods:  We studied 12 male patients with COPD (mean ± SD age, 62.8 ± 10.3 years; FEV1, 28.1 ± 10.2% predicted) and 12 age- and sex-matched healthy subjects (age, 61.1 ± 7.2 years, FEV1, 101.5 ± 11.9% predicted). EMGdi was recorded from a multipair esophageal electrode during a constant work (80% of maximal oxygen consumption derived from a previous incremental exercise test) treadmill exercise. Minute ventilation and oxygen consumption were also measured.

Results:  Root mean square (RMS) of the EMGdi increased initially and reached a plateau at submaximal drive during constant load exercise in both patients with COPD and healthy subjects. The ratio of ventilation to EMGdi remained stable during exercise in healthy subjects from beginning to the end (100% ± 70% at the beginning and 100% ± 39% at the end, P > .05), whereas the ratio decreased gradually during exercise in patients with COPD (from 85% ± 66% to 42% ± 13%, P < .05).

Conclusions:  Efficiency of neural drive decreases in patients with COPD during treadmill exercise. Neural respiratory drive reached a submaximal plateau during constant load exercise in both healthy subjects and patients with COPD, indicating that it may not be the only factor determining exercise capacity.

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