Objectives: To determine the incidence of sleep-related breathing disorders and nocturnal hypoxaemia in patients discharged from ICU following prolonged mechanical ventilation.
Design: Prospective, consecutive patient observational study.
Setting: The medical and surgical wards of a University Hospital.
Patients and participants: Fifteen consecutive, adult patients discharged from the ICU who had received more than 48 h of mechanical ventilation were studied. Ten healthy volunteers acted as controls.
Measurements and results: Overnight, multi-channel pneumographic studies were performed on all patients and controls. Chest and abdominal wall movement, air flow, oxygen saturation and snoring were continuously recorded. Data was analysed by both visual inspection of the traces and by computer-based algorithms. An apnoea/hypopnoea index was calculated for each patient and volunteer. Volunteers had an apnoea/hypopnoea index of less than 5 and had no episodes of nocturnal oxygen desaturation (SaO2 < 90%). Despite oxygen therapy 13/15 patients had episodes of desaturation and 9/15 spent more than 2 h with an SaO2 < 90%. Eleven patients had an abnormal apnoea/hypopnoea index (range 5-34 events/h). Four patients had predominantly obstructive events while 7 primarily had hypopnoeas.
Conclusions: Significant overnight oxygen desaturation is common in patients discharged from ICU who have received prolonged mechanical ventilation. This group also has a significant incidence of sleep-related breathing disorders and this mechanism is likely to be important in the pathogenesis of the hypoxaemia.