Abstract
Background: It has been shown that walking is more sensitive to detect exercise-induced desaturation than cycling in patients with COPD. However, it is unknown whether the same phenomenon occurs between stepping and cycling.
Objective: To compare exercise-induced desaturation and metabolic and ventilatory adaptations during stepping and cycling.
Methods: Twenty-one patients with COPD (FEV1: 47±13% predicted) underwent, on different days, the maximal cardiopulmonary exercise testing (CPET) and incremental step test (IST) performed on a cycle ergometer and a 20-cm bench, respectively. During CEPT, the work rate (WR) was continuously increased (5–15 W.min-1). IST started with 10 steps/minute and increments of one step every 30 seconds until the tolerance limit. Pulse oximetric saturation (SpO2) was recorded every minute in both tests and desaturation was considered a fall ≥ 4% from resting SpO2.
Results: IST induced a higher desaturation compared to CEPT (-6±4.5% vs -3±3%). Seven patients presented desaturation at IST but not at CPET while two patients showed the opposite. Desaturation in both tests and non desaturation in either tests were observed in five and seven patients, respectively. Among the metabolic and ventilatory variables measured at peak exercise, higher oxygen uptake and lower ventilatory equivalent for oxygen were observed for IST as compared with CEPT (1.3±0.4 L/min vs 1.2±0.4 L/min and 33.5±7.4 vs 36.3±7.8; P < 0.05).
Conclusion: The desaturation was detected only during IST in 33% of patients. VO2 peak is higher, ventilatory demand is lower and desaturation more pronounced during stepping than cycling.
- © 2011 ERS