OBJECTIVE

To the evaluate chemo-responsiveness in patients with obesity hypoventilation syndrome (OHS) and respiratory failure (RF).

METHODS

A total of 14 OHS and RF patients with a mean body mass index (BMI) of (34.3 ± 2.68) kg/m(2) hospitalized between January 2009 to December 2011 were recruited. Lung function test (LFT), polysomnograghy (PSG), arterial blood gases (ABG) before and after voluntary hyperventilation maneuver and respiratory responses to hypoxia (ΔVE/ΔSpO(2)) and hypercapnia (ΔVE/ΔPaCO(2)) were measured. Ten of them received bi-level positive airway pressure (BiPAP) for 1 week and pre and post-treatment ABG were compared.

RESULTS

All of them fulfilled the criteria of type II respiratory failure. PSG sleep study indicated a mean sleep apnea hypopnea index of (66.6 ± 30.1) times/h and LFT revealed a predicted FEV(1)/FVC% over 70%, excluding chronic obstruction pulmonary disease. Voluntary hyperventilation maneuver induced significant improvements in PaO(2) (52.5 ± 7.6 vs 81.3 ± 11.1 mmHg (1 mmHg = 0.133 kPa, P = 0.001) and PaCO(2) (50.4 ± 5.3 vs 43.2 ± 1.9 mmHg, P = 0.001). RF was reversed in all patients. As compared with normal controls, all patients had decreased ΔVE/ΔSpO(2) ((-0.11 ± 0.08) vs (-0.38 ± 0.04) L×min(-1)×%SpO(2)(-1), P < 0.001) and ΔVE/ΔPaCO(2) (0.31(0.18, 0.66) vs 1.20 (0.82, 1.50) L×min(-1)×mmHg(-1), P < 0.001). One-week BiPAP therapy induced significant improvement of sleep disordered breathing and daytime ABGs without any change of BMI in 10 patients. And PaCO(2) was normalized in 8/10 patients.

CONCLUSIONS

OHS patients have sleep disordered breathing and depressed chemo-responsiveness. Voluntary hyperventilation maneuver may reverse the "unwilling breathing" type of RF. Non-invasive ventilation treatment may improve nocturnal sleep apnea and daytime ABG abnormality.