Obesity Hypoventilation Syndrome (OHS) is diagnosed in obese (body mass index (BMI) >30kg/m2) patients when awake alveolar hypoventilation (PaCO2 >45 mmHg) cannot be attributed to pulmonary parenchymal disease, skeletal restriction, neuromuscular weakness, or pleural pathology . Most patients with OHS present with the signs or symptoms of chronic hypoventilation, although some may develop acute cardiopulmonary compromise that can be fatal if untreated. Application of positive airway pressure is the mainstay of therapy, regardless of the presentation, or the presence or absence of sleep disordered breathing (eg, obstructive sleep apnea).
In this topic review, positive pressure therapy for patients with OHS is discussed. The pathogenesis, clinical manifestations, diagnosis, and treatment of OHS are discussed separately. (See "Clinical manifestations and diagnosis of obesity hypoventilation syndrome" and "Treatment of the obesity hypoventilation syndrome" and "Pathogenesis of obesity hypoventilation syndrome".)
MODES OF NONINVASIVE POSITIVE PRESSURE THERAPY
There are two major categories of noninvasive positive pressure therapy that are used to treat patients with OHS:
- Continuous positive airway pressure (CPAP)
- Noninvasive positive pressure ventilation (NPPV)
Among the available modes of NPPV, there is bilevel positive airway pressure (BPAP) and volume cycled positive pressure ventilation (VCPPV).