Evaluation of peripheral muscle oxygenation during exercise by spatially resolved spectroscopy in patients with chronic obstructive pulmonary disease.

BACKGROUND

Spatially resolved (SR) spectroscopy has enabled non-invasive and continuous measurement of muscle oxygen saturation during exercise. In patients with chronic obstructive pulmonary disease (COPD), skeletal muscle dysfunction has been widely studied histochemically and biochemically. However, impairment of muscle oxygenation during exercise has not been elucidated yet.

METHODS

We measured oxygen saturation in the vastus lateralis muscle (SmO2) using SR spectrometry during incremental cycle exercise in 16 COPD patients and 10 age-matched healthy subjects.

RESULTS

Significant decrease in SmO2 was found at peak exercise compared with warm-up in both groups (56.9 +/- 6.0% to 47.3 +/- 6.8% in patients with COPD, p<0.001; 60.7 +/- 5.8% to 49.9 +/- 7.7% in healthy subjects, p<0.01). The decrease in SmO2 was linear with respect to increase in work rate, and the slope of SmO2 was significantly steeper in COPD patients than in healthy subjects (-0.282 +/- 0.159 vs -0.107 +/- 0.057 %/Watt, p<0.001). The slope of SmO2 in COPD patients significantly correlated with body mass index (BMI) (p<0.01), peak percutaneous oxygen saturation (p<0.05), and peak pulmonary oxygen consumption (p<0.05). Stepwise regression analysis revealed that BMI was a significant determinant of the SmO2 slope (p=0.01).

CONCLUSIONS

We conclude that oxygenation of peripheral muscle is impaired during exercise in COPD patients and that BMI contributes independently to the change of muscle oxygen saturation with exercise in COPD patients. SR spectroscopy will provide useful information for the study of the dynamics of muscle oxygenation in COPD patients.