Background: Exercise-induced desaturation is a well-described phenomenon in COPD patients during exercise assessments such as the six minute walk test (6MWT). Some of the pathophysiological mechanisms involved in this O2 desaturation could be modified by individualized exercise training as part of a pulmonary rehabilitation programme. The aim of this study was to determine the effect of pulmonary rehabilitation on O2 desaturation exhibited by COPD patients during a 6MWT.
Methods: Twenty COPD patients (FEV1=61.1 +/- 3.2% predicted) who exhibited O2 desaturation before rehabilitation (mean 7.3 +/- 0.7% with a mean duration of 5.3 +/- 0.1 min) participated. They performed four weeks of RP including individualized whole-body exercise training achieving a mean 9.3 +/- 0.27 hours per week of exercise tailored to their ventilatory threshold.
Results: Dyspnoea at the end of the test, ventilatory threshold and FEV1 were retained as correlates of desaturation before rehabilitation. After rehabilitation, 6MWT distance increased (p<0.01) with reduced dyspnoea (p<0.05). Two sub-groups were identified: persistent desaturaters (DS, n=13) and non-desaturaters group (NDS, n=7). There were no baseline differences between the two groups. After rehabilitation only the persistent desaturaters showed a significant increase in distance achieved during 6MWT associated with a reduced dyspnea (p<0.05). This group showed a mean O2 desaturation equal to 8.1 +/- 0.9% which persisted to 5 +/- 0.3 min. A tendency to a lower dyspnoea at the end of 6MWT performed before rehabilitation was observed in NDS compared with DS (p<0.058).
Conclusion: It seems that responses to a pulmonary rehabilitation programme including individualized exercise training could act on O2 desaturation. Indeed 7 of 20 (35%) COPD patients exhibiting O2 desaturation during a 6MWT showed no O2 desaturation after rehabilitation programme while 13 on 20 (65%) do it.