| Mechanism of Greater Oxygen Desaturation during Walking Compared with Cycling in COPD. | |
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MedLine Citation:
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PMID: 21273296 Owner: NLM Status: Publisher |
Abstract/OtherAbstract:
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Abstract BACKGROUND: Patients with chronic obstructive pulmonary disease (COPD) exhibit greater oxyhemoglobin desaturation during walking than with cycling. The purpose of this investigation was to investigate differences in ventilatory responses and gas exchange as proposed mechanisms for this observation. METHODS: Arterial blood gases and lactate were measured in 12 patients with COPD (age, 68 ± 6 years) during incremental treadmill and cycle exercise. The primary outcome to assess the ventilatory response to exercise was the partial pressure of alveolar oxygen (P(A)O(2)). The primary outcome to assess impairment in exercise gas exchange was the difference between partial pressures of alveolar and arterial oxygen (P(a)O(2)) (AaPO(2)). RESULTS: P(a)O(2) was significantly lower at peak exercise for treadmill walking (51.4 ± 6.8 mmHg) compared with cycling (60.4 ± 10.7 mmHg) (p = 0.002). The initial increase in P(A)O(2) with cycling occurred prior to the onset of the anaerobic threshold. At peak exercise, P(A)O(2) was significantly higher with cycling compared with walking (p = 0.004). The anaerobic threshold occurred at a lower VO(2) during cycling than walking (p = 0.001), and peak lactate levels were higher with cycling (p = 0.019). With progressive exercise, AaPO(2) increased similarly during treadmill and cycle exercise. CONCLUSIONS: The higher P(A)O(2) during cycling minimized the magnitude of oxyhemoglobin desaturation compared with walking. The enhanced respiratory stimulation during cycling appears due to an initial neurogenic process, possibly originating in receptors of exercising muscles, and a subsequent earlier onset of anaerobic metabolism with higher lactate levels during cycling. |
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Authors:
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Donald A Mahler; Alex H Gifford; Laurie A Waterman; Joseph Ward; Sasa Machala; John C Baird |
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Publication Detail:
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Type: JOURNAL ARTICLE Date: 2011-1-27 |
Journal Detail:
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Title: Chest Volume: - ISSN: 1931-3543 ISO Abbreviation: - Publication Date: 2011 Jan |
Date Detail:
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Created Date: 2011-1-28 Completed Date: - Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 0231335 Medline TA: Chest Country: - |
Other Details:
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Languages: ENG Pagination: - Citation Subset: - |
Affiliation:
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1 Section of Pulmonary & Critical Care Medicine Dartmouth Medical School, Lebanon, NH, USA. |
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From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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