1. Martel, Gregory PhD

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Pulse oximetry is commonly used to monitor arterial oxygen saturation (SpO2) during exercise in individuals with COPD. However, many patients exhibit poor exercise tolerance despite normal SpO2. Thus, near-infrared spectroscopy (NIRS), which estimates skeletal muscle oxygen saturation (StO2), may be more advantageous than pulse oximetry for monitoring patients with COPD during exercise.



To examine how an incremental treadmill walking test (TMT) effects SpO2, StO2, and calf blood flow (BF) in individuals with COPD (n = 6; 70 +/- 4 yr) and healthy controls (CON; n = 20; 58 +/- 6 yr).



SpO2 and StO2 were assessed at rest, during, and after TMT. The TMT consisted of seven stages with a constant speed of 2.0 mph and 3.5% increases in grade every three minutes. Calf BF was assessed with venous occlusion plethysmography before and after TMT. Independent t-tests and ANOVA with repeated measures were utilized to analyze the data. Significance was set at P <=.05.



There were no significant group differences at rest for StO2 or BF, but SpO2 was significantly higher in CON (97.3 +/- 1.4 vs. 95.5 +/- 1.9 %; P <.05). Although SpO2 stayed above 90% during TMT for both groups, there were greater reductions in SpO2 during the TMT for COPD as compared to CON (all P <.05). Similarly, there was consistently lower StO2 during TMT for COPD compared to CON (all P <=.05). On the contrary, there were similar, significant increases in BF following TMT for both CON and COPD (122% and 114%, respectively; P <.001). Finally, COPD exhibited significantly shorter walking times than CON (11.8 vs. 20.1 min, respectively; P <.05).



Although both groups had similar BF responses to TMT and SpO2 remained within acceptable ranges, COPD had lower StO2 and walking times, indicating that skeletal muscle dysfunction limits exercise capacity in COPD. Thus, NIRS may be an effective device for monitoring those with COPD during aerobic exercise.