In:
Journal of Applied Physiology, American Physiological Society, Vol. 104, No. 5 ( 2008-05), p. 1341-1350
Abstract:
Patients with chronic obstructive pulmonary disease (COPD) have slowed pulmonary O 2 uptake (V̇o 2 p ) kinetics during exercise, which may stem from inadequate muscle O 2 delivery. However, it is currently unknown how COPD impacts the dynamic relationship between systemic and microvascular O 2 delivery to uptake during exercise. We tested the hypothesis that, along with slowed V̇o 2 p kinetics, COPD patients have faster dynamics of muscle deoxygenation, but slower kinetics of cardiac output (Q̇t) following the onset of heavy-intensity exercise. We measured V̇o 2 p , Q̇t (impedance cardiography), and muscle deoxygenation (near-infrared spectroscopy) during heavy-intensity exercise performed to the limit of tolerance by 10 patients with moderate-to-severe COPD and 11 age-matched sedentary controls. Variables were analyzed by standard nonlinear regression equations. Time to exercise intolerance was significantly ( P 〈 0.05) lower in patients and related to the kinetics of V̇o 2 p ( r = −0.70; P 〈 0.05). Compared with controls, COPD patients displayed slower kinetics of V̇o 2 p (42 ± 13 vs. 73 ± 24 s) and Q̇t (67 ± 11 vs. 96 ± 32 s), and faster overall kinetics of muscle deoxy-Hb (19.9 ± 2.4 vs. 16.5 ± 3.4 s). Consequently, the time constant ratio of O 2 uptake to mean response time of deoxy-Hb concentration was significantly greater in patients, suggesting a slower kinetics of microvascular O 2 delivery. In conclusion, our data show that patients with moderate-to-severe COPD have impaired central and peripheral cardiovascular adjustments following the onset of heavy-intensity exercise. These cardiocirculatory disturbances negatively impact the dynamic matching of O 2 delivery and utilization and may contribute to the slower V̇o 2 p kinetics compared with age-matched controls.
Type of Medium:
Online Resource
ISSN:
8750-7587
,
1522-1601
DOI:
10.1152/japplphysiol.01364.2007
Language:
English
Publisher:
American Physiological Society
Publication Date:
2008
detail.hit.zdb_id:
1404365-8
SSG:
12
SSG:
31
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