[Respiration control dysfunction and the relationship to sleep-disordered breathing in patients with chronic obstructive pulmonary disease].

Objective: To analyze the polysomnographic (PSG) features of sleep apnea hypopnea syndrome (SAHS) in patients with chronic obstructive pulmonary disease (COPD), and to define the association between SAHS and respiratory control disorder.
Methods: Three hundred patients with stable COPD were screened for SAHS using questionnaire, Epworth sleep scale (ESS) and home pulse oximeter testing. Those with ESS > or = 10 or oxygen desaturation over 3% more than 5 times per hour sleep were under further PSG testing. The PSG features were compared between COPD patients with apnea hypopnea index (AHI) > 10 and 118 SAHS patients with normal lung function. The two groups were matched for age, body mass index (BMI) and AHI. Among them 22 with COPD and AHI > or = 10 were tested for the chemo-responsiveness to isocapnic hypoxia and hypercapnia.
Results: Among the 300 patients with stable COPD, 79 had AHI over 10, meeting the diagnostic criteria of overlap syndrome (OS). Analysis of the polysomnography found that 32 cases (40%) with OS had more hypoventilation lasting over 1 min during sleep. Compared to patients with SAHS only, OS patients had higher percentage of hypopnea index over AHI [(69 +/- 30)% vs (52 +/- 31)%] and a higher percentage of total hypopnea time over total time of sleep apnea and hypopnea [(15 +/- 12)% vs (12 +/- 10)%]. OS patients also had lower hypoxic [(-0.11 +/- 0.05) vs (-0.35 +/- 0.24) L.min(-1).%(-1)] and hypercapnic responses [(1.1 +/- 0.8) vs (1.6 +/- 0.8) L.min(-1).mm Hg(-1) (1 mm Hg = 0.133 kPa)].
Conclusion: Patients with both COPD and SAHS had more episodes of hypopnea and hypoventilation during sleep, and had depressed chemo-responsiveness to hypoxia during wakefulness.