Prediction of oxygenation during sleep in patients with chronic obstructive lung disease

The accuracy of a prediction equation for assessing the lowest arterial oxygen saturation (SaO2) during sleep was determined in 24 consecutive patients with chronic obstructive lung disease referred for assessment for home oxygen therapy. Subjects had a mean (SD) FEV1 of 0.81 (0.31) litre and an FEV1/FVC of 37% (12%). There was reasonable agreement between predicted and measured values (mean difference [predicted-measured] = -2.5%) but the prediction was not precise as the 95% confidence interval for the difference was +8% to -13%. The duration of arterial oxygen desaturation, defined as the percentage of total sleep time spent below a given SaO2, was not predicted accurately. It is concluded that nocturnal arterial oxygen desaturation in individual patients with chronic obstructive lung disease cannot be predicted from "awake" measurements with sufficient accuracy to be clinically useful.