Cardiac Sympathetic Hyperactivity in Patients with Chronic Obstructive Pulmonary Disease and Obstructive Sleep Apnea.

Obstructive sleep apnea (OSA) and chronic obstructive pulmonary disease (COPD) coexist in 0.5-1% of the general population. Both OSA and COPD are associated with increased sympathetic nervous activity, and patients affected by both disorders have higher risk for increased morbidity and mortality as compared with patients with COPD or OSA alone. We tested the hypothesis that patients with COPD and OSA (Overlap syndrome) have higher sympathetic and lower parasympathetic modulation of heart rate variability (HRV) in comparison with patients suffering from COPD or OSA alone. HRV indices in the frequency domain were evaluated from daytime electrocardiographic recordings in 14 patients with both severe OSA (apnea-hypopnea index ≥ 30) and mild-to-moderate COPD and compared with those with OSA (n = 24) or COPD (n = 16) alone. We found that, in the Overlap syndrome group, high-frequency (HF, 0.4-0.15 Hz) power was significantly lower (0.18 nu vs 0.34 nu in OSA and 0.44 nu in COPD patients, p < 0.01) and low-frequency (LF, 0.15-0.05 Hz) power was significantly greater (0.82 nu vs 0.66 nu in OSA and 0.57 nu in COPD patients, p < 0.01) compared with COPD and OSA groups. Patients with both OSA and COPD had higher LF/HF ratio as compared with patients in OSA and COPD groups (4.5 [5.9] vs 1.9 [2.6] and 1.3 [1.3], respectively, p < 0.01). For the Overlap syndrome group, there was a significant direct relationship between LF/HF ratio and residual volume (r2 = 0.62, p = 0.007). These findings show that patients with both OSA and COPD have higher sympathetic modulation of heart rate compared with those with OSA or COPD alone. Furthermore, the findings provide a potential mechanism for the increased morbidity and mortality reported in patients suffering from both disorders, suggesting new therapeutic perspectives in Overlap syndrome.

Oronasal masks require higher levels of positive airway pressure than nasal masks to treat obstructive sleep apnea.

PURPOSE: The purpose of this study was to compare the therapeutic pressure determined by an automated CPAP device (AutoCPAP) during the titration period, between nasal and oronasal mask and the residual apnea-hypopnea index (AHI) on a subsequent poligraphy performed with the established therapeutic CPAP. METHODS: As a retrospective study, 109 subjects with moderate and severe obstructive sleep apnea-hypopnea (apnea-hypopnea index≥15 events/h) were studied. CPAP titration was performed using an auto-titrating device. RESULTS: There was significant difference in the mean pressure delivered with autoCPAP between the group of patients using the nasal mask (mean 10.0 cmH2O±2.0 SD) and the group which used the oronasal mask (mean 11.2 cmH2O±2.1) (p<0.05). Residual apneas were lower when using a nasal mask: average AHI of 2.6±2.5 compared to 4.5±4.0 using an oronasal mask (p<0.05). On multivariate analysis, the only independent predictor of the level of therapeutic pressure of CPAP was the type of mask used (r=0.245, p 0.008). CONCLUSIONS: Therapeutic CPAP level for OSAH is higher when administered via oronasal mask, leaving more residual events. These findings suggest that nasal mask should be the first choice for OSAH treatment.