Background: The obesity-hypoventilation syndrome (OHS), commonly defined as a combination of obesity and diurnal hypercapnia, is efficiently treated using nasal positive pressure ventilation (NPPV). The present study aimed to determine whether nocturnal polysomnography allows detection of respiratory disturbances occurring in patients with OHS treated with NPPV that may interfere with the quality of sleep and of ventilatory support, and are not detected by nocturnal pulse oximetry and capnography.
Methods: Twenty OHS patients in stable clinical condition treated by NPPV for at least 3 months with a bilevel pressure support ventilator were studied. All patients underwent single-night polysomnography under NPPV including transcutaneous measurement of Pco(2) (TcPco(2)). Four types of respiratory events were defined and quantified: patient/ventilator desynchronization, periodic breathing (PB), autotriggering, and apnea-hypopneas.
Results: Eleven patients (55%) exhibited desynchronization occurring mostly in slow-wave sleep and rapid eye movement sleep and associated with arousals but not inducing significant changes in TcPco(2) or oxygen saturation using pulse oximetry (Spo(2)). Eight patients (40%) showed a high index of PB, mostly occurring in light sleep and associated with more severe nocturnal hypoxemia. Autotriggering was sporadic and usually limited to one or two breaths, although prolonged and asymptomatic autotriggering occurred in one patient during 10.6% of total sleep time.
Conclusions: Patient/ventilatory asynchrony and PB are respiratory patterns occurring frequently in OHS patients treated using NPPV. Nocturnal monitoring of Spo(2) and TcPco(2), commonly used to assess the efficacy of ventilatory support, do not adequately explore this aspect of therapy that might influence its efficacy as well as sleep quality.