Chronic Obstructive Pulmonary Disease and Sleep Disordered Breathing - The Overlap Syndrome: An Evolving Clinical Phenotype
Sleep disturbances are common in chronic obstructive pulmonary disease (COPD) and are often associated with sleep disordered breathing in the form of nocturnal oxygen desaturation, obstructive sleep apnea (OSA), and hypoventilation. The respiratory changes during sleep in COPD have profound effects on sleep quality and quality of life. In addition, the physiologic alterations that result from the disordered breathing likely aggravate certain COPD-related complications, such as pulmonary hypertension, and possibly may increase mortality. Recently, the focus on specific clinical phenotypes such as upper lobe predominant emphysema, frequent exacerbators, and presence of peripheral muscle dysfunction have advanced the approaches to therapy that are affecting outcomes. It is likely that patients with coexistent COPD and sleep disordered breathing (the overlap syndrome) define another clinical phenotype that have a significant impact on the natural history of the disease. Studies have shown a high prevalence of OSA among patients with COPD and that such patients have a higher mortality despite treatment. This effect could perhaps be mediated via mechanisms involving comorbidities, including cardiovascular disease and metabolic syndromes. Current interventions, like supplemental oxygen, positive airway pressure support, and lung volume reduction improve the well being and survival of some patients with COPD, but the optimal therapy for the COPD overlap phenotype remains to be determined.
Keywords: Overlap syndrome, chronic obstructive pulmonary disease, sleep apnea, chronic bronchitis, emphysema, hypoventilation
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