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Background
Cardiorespiratory fitness (CRF) is an important prognostic marker in chronic obstructive pulmonary disease (COPD). Obstructive sleep apnea (OSA) also negatively affects exercise tolerance. However, the impact of their association on CRF has not been evaluated. We hypothesized that patients with overlap syndrome would demonstrate a greater impairment in CRF, particularly those with severe COPD.
Methods
Individuals with COPD were recruited. First, subjects underwent clinical and spirometry evaluation. Next, home-based sleep evaluation was performed. Subjects with an apnea-hypopnea index (AHI) < 15 episodes/h were allocated to the COPD group and those with an AHI ≥ 15 episodes/h to the overlap group. On the second visit, subjects underwent a cardiopulmonary exercise test. Subsequently, they were divided into four groups according to the severity of COPD and coexistence of OSA: COPDI/II; overlap I/II; COPDIII/IV; and overlap III/IV.
Results
: Of the 268 subjects screened, 31 were included. The overlap group exhibited higher values for peak carbon dioxide (COPD: 830 [678–1157]; overlap: 1127 [938–1305] mm Hg;
p
< 0.05), minute ventilation (COPD: 31 [27–45]; overlap: 48 [37–55] L;
p
< 0.05), and peak systolic blood pressure (COPD: 180 [169–191]; overlap: 220 [203–227] mm Hg;
p
<; 0.001) and peak diastolic blood pressure COPD: 100 [93–103]; overlap: 110 [96–106] mm Hg;
p
< 0.001). COPD severity associated with OSA produced a negative impact on exercise time (COPDIII/IV: 487 ± 102; overlap III/IV: 421 ± 94 s), peak oxygen uptake (COPDIII/IV: 12 ± 2; overlap III/IV: 9 ± 1 ml.Kg.min
−1
;
p
< 0.05) and circulatory power (COPDIII/IV: 2306 ± 439; overlap III/IV: 2162 ± 340 ml/kg/min.mmHg;
p
< 0.05).
Conclusion
Overlap syndrome causes greater hemodynamic and ventilatory demand at the peak of dynamic exercise. In addition, OSA overlap in individuals with more severe COPD impairs CRF.