[Obesity hypoventilation syndrome--serious but reversible providing weight is lost]

Obesity hypoventilation syndrome (OHS) is a condition in which obesity and chronic hypoventilation during waking hours are combined. Patients with OHS are more likely to be hospitalized and to require intensive-care monitoring compared with patients with similar degrees of obesity without hypoventilation. Treatment with chronic non-invasive positive pressure ventilation (NPPV) is associated with a lower morbidity and mortality. We present 2 cases of OHS; in the first case, a 56-year-old woman, we show that it is very important to diagnose and treat OHS at an early stage in order to avoid severe morbidity. In the second case, a 31-year-old man, we show that if a patient with OHS and chronic NPPV looses a significant amount of weight NPPV can be discontinued. Patients with OHS should be treated in a multidisciplinary team in order to achieve significant weight loss, so NPPV could be a temporary treatment or even be avoided.