Obesity hypoventilation syndrome (OHS) is defined as a combination of obesity (body mass index Ն 30 kg/m2 ), daytime hypercapnia (partial arterial carbon dioxide concentration Ն45 mm Hg) and sleepdisordered breathing after ruling out other disorders that may cause alveolar hypoventilation. Through the prism of the International Classification of Functioning, OHS is a chronic condition associated with respiratory, metabolic, hormonal and cardiovascular impairments, leading to a decrease in daily life activities, a lack of social participation and high risk of hospitalization and death. Despite its severity, OHS is largely underdiagnosed and the health-related costs are higher than those of apnoeic or obese eucapnic patients. The present review discusses the definition, epidemiology, physiopathology and treatment modalities of OHS. Although nocturnal positive airway pressure therapies represent first-line treatment and are effective in improving patient outcomes, there is a need to offer combined treatment strategies and to assess the effect of multimodal therapeutic strategies on morbidity and mortality.The Authors: Jean-Christian Borel, PhD, is the Head of the Research and Development Department at 'AGIR à dom', a non-profit home care provider. He has developed an expertise in the field of non-invasive ventilation, home-based training programmes and integrated care. He carried out his PhD thesis at the Hypoxia Pathophysiology Laboratory (HP2) on the clinical and cardiovascular consequences of the obesity hypoventilation syndrome, followed by a postdoctoral fellowship on the pathophysiology of the sleep apnoea syndrome in Dr Frederic Series' team at the Quebec Heart and Lung Institute.Anne-Laure Borel, MD, PhD from Grenoble University Hospital, France, has completed a postdoctoral fellowship in Quebec, Canada in Dr Jean-Pierre Despres' team of the Quebec Heart and Lung Institute. She is an endocrinologist with a clinical activity focused on obesity and type 2 diabetes. Her research interests are in the field of the cardiometabolic complications of an excess visceral adiposity and more specifically, the association between sleep-disordered breathing, excess visceral fat and metabolic abnormalities.Denis Monneret, MSc, PhD, is a pharmacist with a diploma of medical biology from Lille Faculty of Pharmacy, France. His MSc and PhD degrees specialized in biology of obstructive sleep apnoea and obesity hypoventilation syndrome. After working as Assistant Professor in the Biochemistry and Hormonology Unit at Grenoble University Hospital, he joined the HP2 Laboratory where he works on oxidative stress and metabolic biomarkers of obstructive sleep apnoea, and obesity hypoventilation syndrome.Renaud Tamisier, MD, PhD, is an Associate Professor of Physiology at Grenoble University School of Medicine, France. He works in the HP2 Laboratory and has been involved in both research and clinical studies in sleep-disordered breathing for the last 15 years. His research interests are mainly on the cardiovascular consequence...
