Changes in Skeletal Muscle Oxygenation during Dynamic Exercise in Patients with Respiratory Failure.

The purpose of this study was to investigate tissue oxygen saturation during a single knee extension exercise in seven chronic respiratory disease patients (CRF) and six age-matched controls. The subjects performed three minutes of dynamic knee-extension exercises at two different intensities, as no weight exercise and 10% maximal voluntary contraction (MVC) exercise. Tissue oxygen saturation (SO2NIRS = oxygenate hemoglobin/total hemoglobin) in the vastus lateralis muscle was measured by continuous-wave NIRS (NIRS: near-infrared spectroscopy). The relative changes in SO2NIRS (ΔSO2NIRS) was expressed by changes from resting value, and two-way analysis of variance (ANOVA) with repeated measurements used to evaluate the overall comparisons of exercise responses between the CRF and control groups. There was no significant change in quadriceps muscle force between the CRF and control group (208.7 ± 19.6 N; mean ± SE, 234.7 ± 25.9 N, respectively). ΔSO2NIRS during exercise showed a significant difference between the two groups during no-weight and 10%MVC exercises (p<0.01, p<0.05, respectively), while SaO 2 did not show any significant difference. We concluded that CRF subjects demonstrated a lower tissue oxygen saturation during exercise than did healthy older ones, and this difference could be explained by the changes in oxygen supply and/or consumption in the exercised muscle.