Kinetics of muscle deoxygenation are accelerated at the onset of heavy-intensity exercise in patients with COPD: relationship to central cardiovascular dynamics
Key result
Moderate-to-severe COPD was associated with slower kinetics of pulmonary O2 uptake (73 vs 42 s) and cardiac output (96 vs 67 s) but faster muscle deoxygenation (16.5 vs 19.9 s) than controls.
Why the study?
Does moderate-to-severe COPD alter the kinetics of muscle deoxygenation and cardiac output during heavy-intensity exercise compared to healthy controls?
Population
10 patients with moderate-to-severe COPD and 11 age-matched sedentary controls (total n=21)
Comparison
Heavy-intensity exercise performed to the limit… vs Age-matched sedentary controls performing the…
Design
Case-control
Authors
Discussion
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Implication
Impaired central-peripheral O2 delivery kinetics may limit exercise tolerance in COPD; hypothesis-generating for interventions targeting these adjustments.
Key Points
- To determine how moderate-to-severe COPD affects the dynamic relationship between systemic and microvascular oxygen delivery and muscle oxygen uptake during heavy-intensity exercise.
- Assessed 10 patients with moderate-to-severe COPD and 11 age-matched sedentary controls during heavy-intensity cycling to the limit of tolerance.
- Measured pulmonary oxygen uptake, cardiac output using impedance cardiography, and muscle deoxygenation using near-infrared spectroscopy, analyzing kinetics with standard nonlinear regression equations.
- Compared with controls, COPD patients exhibited significantly slower kinetics of pulmonary oxygen uptake (73 ± 24 vs. 42 ± 13 s) and cardiac output (96 ± 32 vs. 67 ± 11 s), but faster overall muscle deoxygenation kinetics (16.5 ± 3.4 vs. 19.9 ± 2.4 s).
- Time to exercise intolerance was significantly lower in COPD patients (P < 0.05) and inversely correlated with pulmonary oxygen uptake kinetics (r = -0.70; P < 0.05).
- The ratio of oxygen uptake time constant to mean response time of deoxygenated hemoglobin was significantly greater in COPD patients, reflecting impaired microvascular oxygen delivery.
Study Design
Type
Observational (n=21)
Structured PICO
Does moderate-to-severe COPD alter the kinetics of muscle deoxygenation and cardiac output during heavy-intensity exercise compared to healthy controls?
P
Population
10 patients with moderate-to-severe COPD and 11 age-matched sedentary controls who performed heavy-intensity exercise to the limit of tolerance.
E
Exposure
Heavy-intensity exercise performed to the limit of tolerance
C
Comparator
Age-matched sedentary controls performing the same exercise
O
Outcome
Kinetics of pulmonary O2 uptake (Vo2(p)), cardiac output (Qt), and muscle deoxygenation (deoxy-Hb)surrogate
Patients with moderate-to-severe COPD have impaired central and peripheral cardiovascular adjustments during heavy-intensity exercise, which may contribute to slower oxygen uptake kinetics.
Cite This Study
Chiappa et al. (2008) conducted an observational in Chronic obstructive pulmonary disease (COPD) (n=21). Moderate-to-severe COPD vs. Age-matched sedentary controls was evaluated on Kinetics of pulmonary O2 uptake (Vo2(p)), cardiac output (Qt), and muscle deoxygenation. Moderate-to-severe COPD was associated with slower kinetics of pulmonary O2 uptake (73 vs 42 s) and cardiac output (96 vs 67 s) but faster muscle deoxygenation (16.5 vs 19.9 s) than controls.