Key result
COPD patients who developed low muscle pH during exercise had a significantly shorter time delay in muscle deoxygenation kinetics (5.5 seconds) compared to healthy controls (11.6 seconds).
Why the study?
Do muscle oxygenation kinetics during the transition from rest to exercise differ between patients with COPD and healthy individuals?
Cross-Sectional (n=23)
No
Do muscle oxygenation kinetics during the transition from rest to exercise differ between patients with COPD and healthy individuals?
Patients with COPD who develop low muscle pH during exercise exhibit a shorter time delay in muscle deoxygenation kinetics, suggesting impaired muscle O2 delivery during the transition to exercise.
Answers are grounded in this paper and cite their sources.
Muscle oxygenation may differ during exercise in COPD; leaves open impact on capacity and need for targeted studies.
Exercise capacity is frequently decreased in patients with chronic obstructive pulmonary disease (COPD), and muscle dysfunction is one factor in this reduction. Studies using (31)-phosphorus magnetic resonance spectroscopy ((31)P-MRS) have shown that phosphocreatine (PCr) and muscle pH (pHi) are significantly decreased in patients with COPD during mild exercise, suggesting the early activation of anaerobic glycolysis in their muscles. Thus, muscle oxygenation states during exercise might differ between patients with COPD and healthy individuals. We simultaneously measured oxygenation state and pHi in the muscles of patients with COPD during the transition from rest to exercise (on-transition) using near infrared spectroscopy (NIRS) and (31)P-MRS. Sixteen patients with COPD (aged 68.6 +/- 7.5 years) and 7 healthy males (controls; aged 63.3 +/- 7.5 years) performed dynamic handgrip exercise (lifting a weight by gripping at a rate of 20 grips per min for 3 min). Patients were classified based on pHi data at the completion of exercise as having a normal (>or= 6.9; n = 8) or a low (< 6.9; n = 8) pHi. The deoxygenated hemoglobin/myoglobin (deoxy-Hb/Mb) in NIRS recordings remained constant or slightly decreased initially (time delay), then increased to reach a plateau. We calculated the time delay and the time constant of deoxy-Hb/Mb kinetics during the on-transition. The time delay was shorter in the group with a low pHi than in the controls. These findings might reflect a slower increase in O(2) delivery in patients with a low pHi, which might partly account for altered muscle energy metabolism.
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Kutsuzawa et al. (2009) conducted a cross-sectional in Chronic Obstructive Pulmonary Disease (COPD) (n=23). COPD with low muscle pH during exercise vs. Healthy controls was evaluated on Time delay (TD) of deoxygenated hemoglobin/myoglobin kinetics (p=<0.01). COPD patients who developed low muscle pH during exercise had a significantly shorter time delay in muscle deoxygenation kinetics (5.5 seconds) compared to healthy controls (11.6 seconds).
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