We tested the efficacy of nocturnal nasal ventilation (NNV) using the BIPAP
ventilator in patients with restrictive
thoracic diseases by withdrawing them from NNV for an average of 1 wk. One male and five female patients were enrolled in the study; four with restrictive chest wall diseases, and two with
muscular dystrophies. All patients had chronic CO2 retention (PaCO2 greater than 50 mm Hg) and had been improved by using NNV for at least 2 months before the study. Four patients were switched to the BIPAP
ventilator from standard portable volume
ventilators at least 1 month prior to the study without changes in gas exchange or symptoms. After withdrawal of NNV, patients had no deterioration in daytime vital signs, pulmonary functions, maximal inspiratory or expiratory pressures, or arterial blood
gases compared with measures made immediately before withdrawal and 1 wk after resumption. However, patients had more
dyspnea at rest, increased
daytime somnolence, more morning
headaches, less daytime energy, and felt less rested in the morning during withdrawal of NNV. Furthermore, nocturnal monitoring demonstrated greater
tachycardia,
tachypnea,
oxygen desaturation, and
hypoventilation during withdrawal of NNV. We conclude that NNV administered by the BIPAP
ventilator is effective in ameliorating nocturnal
hypoventilation and daytime symptoms in patients with chronic CO2 retention caused by severe restrictive
thoracic diseases. These data also suggest that the efficacy of NNV may depend more on amelioration of nocturnal
hypoventilation than on resting of ventilatory muscles.