Previous studies have addressed the efficacy of aCPAP devices in home therapy of OSAS over several weeks. A randomized study14 including eight patients treated for 3 weeks with the Morphée autoCPAP device (Pierre Medical; Verrieres le Buisson, France) in automatic mode and eight patients in constant mode revealed a better compliance in the aCPAP group of 6.5 h per night vs 5.1 h per night in the cCPAP group. In 1997, Sériès and Mark13 demonstrated in a small (n = 10) cross-over study a similar AHI when patients were treated with the Morphée aCPAP device compared to manually titrated cCPAP. In a single-blind parallel study, Konermann et al9 found better compliance, sleep quality, and lower treatment pressures with aCPAP with the Horizon machine (De Vilbiss; Somerset, PA) compared to cCPAP. However, no data on daytime vigilance were available for this cohort.9 A similar parallel study31 using the Somnosmart device (Weinmann; Hamburg, Germany) also reported lower treatment pressures and higher preference for aCPAP, but no objective data about daytime vigilance were available either. In a randomized cross-over study,12 44 patients selected according to their requirements for a high therapeutic pressure ≥ 10 cm of H2O were treated with AutoSet T or with manually titrated fixed pressure over 6 weeks each. The AutoSet T (ResMed; North Ryde, Australia) mode was superior in sleep symptom scores, SF-36 vitality, and mental health scores. Moreover, median treatment pressures were lower and adherence per night was significantly better with the autoadjusting device, but objective vigilance was not assessed. In a randomized trial,10 of two aCPAP devices vs cCPAP addressing objective and subjective sleepiness, nocturnal breathing disturbances, treatment adherence, and quality of life, no differences between cCPAP and aCPAP by the two tested devices (AutoAdjust LT; DeVilbiss; AutoSet T; ResMed) were found.