| Characteristic | Before nCPAP | After nCPAP | p-value |
| Subjects n | 29 | 29 | |
| AHI | 27±3 | 4±2 | <0.0001 |
| Arousal index# | 14±2 | 10±1 | <0.05 |
| Sleep efficiency % | 76±2 | 81±4 | <0.05 |
| Stage wake min | 103±9 | 66±9 | <0.01 |
| Total sleep time min | 316±8 | 349±17 | <0.01 |
| Sleep stage 1 % of total sleep time | 10.9±2.9 | 5.6±1,7 | 0.16 |
| Sleep stage 2 % of total sleep time | 57.6±3.2 | 52.6±3.1 | 0.35 |
| Delta sleep stage 3+4, % of total sleep time | 19.9±2.1 | 27.6±2.8 | <0.05 |
| Sleep stage REM % of total sleep time | 11.6±1.4 | 14.2±1.4 | 0.17 |
| Minimum nocturnal Sa,O2 % | 77±2 | 86±1 | <0.0001 |
| Mean nocturnal Sa,O2 % | 93±0 | 94±0 | <0.0001 |
| Sa,O2 <90% % | 19±4 | 4±1 | <0.0001 |
| ODI | 26±3 | 0±0 | <0.0001 |
| Change of reflective index¶ during the night % of awake value | 10±3 | 6±4 | <0.05 |
Data are presented as mean±sem, unless otherwise stated. AHI: apnoea/hypopnoea index (mean number of episodes of apnoea and hypopnoea per hour of sleep); REM: rapid eye movement; Sa,O2: arterial oxygen saturation; ODI: oxygen desaturation index. #: the arousal index is the mean number of arousal reactions per hour of sleep; ¶: reflective index at 05.00 h is given as percentage of the reflective index of the patient awake in the lying position before the start of the polysomnography.