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Clinical Investigations: COPD |

Effect of Hyperoxia on Gas Exchange and Lactate Kinetics Following Exercise Onset in Nonhypoxemic COPD Patients*

Attila Somfay, MD; János Pórszász, MD, PhD; Sang-Moo Lee, MD; Richard Casaburi, PhD, MD, FCCP
Author and Funding Information

*From the Rehabilitation Clinical Trials Center, Harbor-UCLA Research and Education Institute, Torrance, CA.

Correspondence to: Richard Casaburi, PhD, MD, FCCP, Division of Respiratory and Critical Care Physiology and Medicine, Harbor-UCLA Research and Education Institute, Building RB2, 1124 W Carson St, Torrance, CA 90502; e-mail: casaburi@ucla.edu



Chest. 2002;121(2):393-400. doi:10.1378/chest.121.2.393
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Study objectives: The slow oxygen uptake (V̇o2) kinetics observed in COPD patients is a manifestation of skeletal muscle dysfunction of multifactorial origin. We determined whether oxygen supplementation during exercise makes the dynamic V̇o2 response faster and reduces transient lactate increase.

Design: Ten patients with severe COPD (ie, mean [± SD] FEV1, 31 ± 10% predicted) and 7 healthy subjects of similar age performed four repetitions of the transition between rest and 10 min of moderate-intensity, constant-work rate exercise while breathing air or 40% oxygen in random order. Minute ventilation (V̇e), gas exchange, and heart rate (HR) were recorded breath-by-breath, and arterialized venous pH, Pco2, and lactate levels were measured serially.

Results: Compared to healthy subjects, the time constants (τ) for V̇o2, HR, carbon dioxide output (V̇co2), and V̇e kinetic responses were significantly slower in COPD patients than in healthy subjects (70 ± 8 vs 44 ± 3 s, 98 ± 14 vs 44 ± 8 s, 86 ± 8 vs 61 ± 4 s, and 81 ± 7 vs 62 ± 4 s, respectively; p < 0.05). Hyperoxia decreased end-exercise V̇e in the COPD group but not the healthy group. Hyperoxia did not increase the speed of V̇o2 kinetics but significantly slowed V̇co2 and V̇e response dynamics in both groups. Only small increases in lactate occurred with exercise, and this increase did not correlate with the τ for V̇o2.

Conclusion: In nonhypoxemic COPD patients performing moderate exercise, the lower ventilatory requirement induced by oxygen supplementation is not related to improved muscle function but likely stems from direct chemoreceptor inhibition.

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