Sleep & breathing = Schlaf & Atmung
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We retrospectively evaluated data from 213 consecutive patients; 152 were affected by obstructive sleep apnea (OSA), 29 had OSA associated with chronic obstructive pulmonary disease (COPD), also known as overlap syndrome, and 32 had COPD. Patients with obesity-hypoventilation syndrome were not included. The aims of the study were to evaluate the anthropometric, pulmonary, and polysomnographic characteristics of patients affected by overlap syndrome compared to "simple" OSA and to COPD subjects and to analyze the determinants of hypercapnia in overlap syndrome. ⋯ Anthropometric, pulmonary function, and polysomnographic data did not differ between normo- and hypercapnic overlap patients. The best model (stepwise multiple regression analysis) for predicting PaCO2 in overlap patients showed r2 value 0.65: PaO2 contributed to 38%, FEV1 to 15%, and weight to 12%. In conclusion, the occurrence of hypercapnia in overlap patients is only partially explained by the combination of overweight and reduced respiratory function, supporting the hypothesis of a multifactorial genesis.
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We assessed the effects of chronic nasal continuous positive airway pressure (CPAP) therapy on lung function in a series of unselected patients with overlap syndrome, and we determined whether there were differences in the response induced by CPAP between hypercapnic (PaCO2 > or =45 mm Hg) and eucapnic patients with overlap syndrome. The study population included 55 unselected patients (48 men, mean age of 58.5 +/- 10.5 years) with a concurrent diagnosis of chronic obstructive pulmonary disease (COPD) and obstructive sleep apnea-hypopnea syndrome (OSAHS) who had been referred to the Department of Pulmonology of our hospital over 2 consecutive years and in whom work-up studies resulted in the prescription of nasal CPAP therapy. An apnea-hypopnea index (AHI) greater than or equal to 10 in the cardiorespiratory polygraphy was required for the diagnosis of OSAHS. ⋯ After 6 months of CPAP therapy, there were statistically significant increases in PaO2, FEV1, and FVC, accompanied by significant decreases in PaCO2, serum bicarbonate levels, and alveolar-arterial oxygen difference. Response of overlap syndrome patients to CPAP therapy was superior in the hypercapnic group, particularly in relation to improvement of arterial blood gases. However, statistically significant differences in all parameters for the comparison between 6 and 18 months were not recorded.