Abstract
Introduction: The determinants of the critical power (CP) for whole-body exercise (lower limbs) in patients with COPD have been previously identified. There are no data concerning to its determinants for upper limbs (UL) in this population. Objective: To characterize the determinants of the CP for UL in patients with COPD. Methods: Eight patients with COPD (FEV1: 45.1±1.2% of predicted) and seven healthy subjects were assessed. After an arm incremental test on cycle ergometer, three constant workload tests were performed (100-120%, 90% and 80% of peak workload). From these tests the CP was estimated and an additional test was performed (5-20% above the workload of the estimated CP). Then, CP was determined by the intercept of the linear regression between workload and reciprocal of time for the four tests and was confirmed in a new test. The inspiratory capacity (IC) was measured before and immediately after each test. Results: There was no significant difference in the CP workload between patients and controls (30.2±12.7 Watts - 59.8±11.4% of peak workload vs 42.2±16.7 Watts - 66.7±9.3% of peak workload, respectively). The oxygen uptake in CP was lower in the COPD group than controls (0.79±0.28 L/min vs 1.20±0.37 L/min, respectively, p<0.05). The patients presented dynamic hyperinflation and substantial reduction of ventilatory reserve for all tests, including the CP test. Despite the ventilatory limitation, all patients were able to sustain exercise at CP for 20 minutes. Conclusion: The present study shows that the ventilatory constraint is the most important determinant of the CP for UL exercise in COPD patients.
- © 2012 ERS
