Randomised, sham placebo, parallel study of the effect of Nasal Continuous Positive Airway Pressure (NCPAP) on steering performance in patients with Obstructive Sleep Apnoea (OSA) - interim analysis
Steering a car involves the two visual functions of predicting road curvature and maintaining road position (Nature 1995;377:339-340). OSA patients show substantial impairment in these visual tasks of steering on a simulator, compared to normals (AJRCCM 1998; 157: A50). 38 untreated OSA patients (Epworth sleepiness score > 9, and >10/hr > 4% SaO2 dips) have so far been randomised to receive placebo or real NCPAP. Placebo NCPAP is provided by using a mask pressure <2 cmsH2O (achieved by adjusting the pressure setting to 3 cmsH2O and providing extra air leaks at the mask). All patients performed three simulator drives at entry to the study and at one month following treatment. Each drive involves steering along a road display that bends pseudo-randomly for thirty minutes. Performance is quantified as the standard deviation (SD) of the steering error from the theoretical perfect path (AJRCCM 1996;154:175-81). Results are the mean (SEM) of the standard deviation of steering error for 16 patients on real NCPAP, and 22 on placebo; significance by unpaired T test. Pre Post Pre Post Significance of Real Real Placebo Placebo changes produced by real v placebo mean SD of 0.47 0.28 0.44 0.44 p = 0.038 steering (SEM) 0.07 0.04 0.07 0.07 Compliance over the 4 weeks was 5.6 and 4.7 hrs/night, real and placebo respectively (NS). Compared to the placebo treated group, OSA patients treated with real NCPAP show a significant improvement in the visual tasks of steering.