Author(s): GUTIERREZ, S., MIRANDA, C., VALDES, O., JALÓN, M., MENDOZA, L., PEÑAILILLO, L., Institution: UNIVERSITY ANDRÉS BELLO, Country: CHILE, Abstract-ID: 1013

INTRODUCTION:
Chronic obstructive pulmonary disease (COPD) is a leading cause of death worldwide, with muscle dysfunction in the lower limbs being a significant extrapulmonary manifestation (1). Muscle dysfunction is characterized by loss of muscle mass and function, resulting in limited exercise capacity and reduced quality of life. Systemic inflammation and oxidative stress are common manifestations of COPD and could impair muscle energy metabolism and oxygen utilization (2). These factors compromise oxygen delivery to muscles during exercise, affecting exercise performance in patients. In COPD patients, these factors likely contribute to early fatigue and reduced maximal aerobic capacity. Near-infrared spectroscopy (NIRS) provides a non-invasive method to assess muscle oxygenation in real time, offering insight into oxygen supply and utilization during exercise (3). This study aimed to compare muscle oxygen supply and uptake during a submaximal time to exhaustion (TTE) cycling test in COPD patients and healthy individuals.
METHODS:
A cross-sectional observational study compared 12 healthy individuals (64 ± 6.7 years and FEV1 104.67% ± 7.63) and 12 patients with severe COPD (65 ± 5.3 years and FEV1 40.67% ± 15.67). Maximal aerobic capacity (VO2peak) and power output (POmax) were measured using an incremental cycling test. The time-to-exhaustion (TTE) test was assessed with a constant-load test at 70% of the POmax. During TTE, muscle oxygenation was measured using NIRS in the vastus medialis, which assesses the concentration of total hemoglobin plus the concentration of myoglobin (tHbMb) in the muscle in real time and the percentage of muscle oxygen saturation (SmO2). Furthermore, deoxyhemoglobin (HHb) was calculated as the tHbMb multiplied by the SmO₂ fraction. The area under the curve (AUC) of the variables SmO₂, tHbMb, and HHb over time of TTE was calculated to represent the cumulative response. Additionally, heart rate, peripheral oxygen saturation (SpO2), and perceived exertion (Borg´s scale) were recorded during TTE. Data analysis was performed in RStudio using Student’s t-test and analysis of variance (ANOVA).
RESULTS:
COPD patients show a 29.1% lesser VO₂peak (p=0.02) compared to healthy individuals. COPD patients performed 43.6% lesser time in the TTE than healthy individuals. The AUC during exercise time in TTE of HHb was 44.9% (p=0.04) lower in COPD patients, likely due to the significantly shorter TTE duration (p<0.01). The SmO2 was similar (56.4% vs 51.2%, respectively) between groups (p=0.28). However, SmO2 at 10% of the total time was 15% lower (p = 0.02) in healthy individuals than COPD, indicating reduced muscle oxygen uptake. The tHbMb increased similarly in both groups (p=0.94), reflecting comparable vascular responses.
CONCLUSION:
This suggests that COPD patients have a reduced capacity to sustain submaximal effort, potentially due to lesser maximal oxidative capacity and impaired muscle oxygen delivery and utilization during exercise, which may lead to early fatigue.