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Official Journal of the Italian Society of Thoracic Endoscopy
Indexed/Abstracted in: EMBASE, Scopus
Department of Pulmonary Medicine and Multidisciplinary Sleep Disorders Centre, Antwerp University Hospital and University of Antwerp, Edegem, Belgium
Obesity hypoventilation and overlap syndrome are a growing health concern, owing to the worldwide obesity and COPD epidemy and related morbidities. These disorders constitute the end points of a spectrum with distinct yet interrelated mechanisms that lead to substantial burden. The pathophysiology of obesity hypoventilation results from complex interactions, among which are respiratory mechanics, ventilatory control, sleep-disordered breathing and neurohormonal disturbances, such as leptine resitance, with only some morbidly obese patients that develop awake hypoventilation. This respiratory embarrassment takes place when compensatory mechanisms fail or become overwhelmed. The coexistence of obstructive sleep apnea and COPD, defined as overlap syndrome, seems to occur by chance, but can mutually contribute to worsened symptoms and oxygenation at night, leading to disrupted sleep architecture and decreased sleep quality. Alveolar hypoventilation, ventilation-perfusion mismatch and intermittent hypercapnic events resulting from apneas and hypopneas contribute to the final clinical picture, which is quite different from “usual” COPD. Although a unifying concept for the pathogenesis of both disorders is lacking, it seems that these patients are in a vicious cycle. This review outlines the major mechanisms believed to contribute to the development of these specific clinical entities. Knowledge of common mechanisms in obesity hypoventilation and overlap syndrome may help to identify these patients and guide therapy.