[Obesity and obesity hypoventilation syndrome]

Some patients with obesity show chronic hypercapnia while awake. Such patients are referred to as obesity hypoventilation syndrome(OHS). Particularly, patients with profound obesity who have clinical features of sleep disordered breathing, hypersomnolence, cor pulmonale and so on represent the Pickwickian syndrome. The mechanisms of hypoventilation in OHS are multifactorial. The level of the blunted chemosensitivity, mechanical impairments of the respiratory system, the severity of the sleep-disordered breathing, and chronic hypoxemia may be important determinants of chronic hypoventilation. In this paper, the characteristics of pulmonary functions in obesity and the possible mechanisms of hypoventilation in patients with OHS were reviewed. Furthermore, the definition of OHS and descriptions of thr severity of OHS as recommended by Respiratory Failure Research Committee of Japanese Ministry of Health and Welfare are introduced.