Purpose <p>Positive airway pressure (PAP) is the standard therapy for obstructive sleep apnea (OSA), delivered as continuous PAP (CPAP) or auto-adjusting PAP (APAP). While both reduce obstructive events, their impact on sleep continuity during the first PAP night and the role of pressure dynamics remain unclear. This study compared the effects of APAP and CPAP on sleep continuity during the first in-laboratory PAP night in OSA and assessed the influence of PAP dynamics.</p> Methods <p>In this retrospective study, 108 adults with OSA underwent diagnostic polysomnography (PSG) and an in-laboratory PSG with PAP (APAP, <i>n</i> = 54; CPAP, <i>n</i> = 54). Sleep continuity, sleep stages, and respiratory indices were recorded. PAP device data were used to quantify pressure changes, pressure range, and 95th percentile pressure, which were correlated with changes in total sleep time (TST), wake after sleep onset (WASO), and sleep efficiency.</p> Results <p>Baseline characteristics and apnea-hypopnea index (AHI) were similar between groups. Both APAP and CPAP markedly reduced AHI without significant between-group differences. APAP was associated with decreased TST, increased WASO, and reduced sleep efficiency, while these measures remained stable with CPAP. APAP also showed more frequent and wider pressure changes and higher 95th percentile pressures, demonstrating modest correlations with poorer sleep continuity.</p> Conclusion <p>During the first PAP night, APAP and CPAP achieved comparable respiratory control. However, APAP was associated with disrupted sleep continuity and increased wakefulness, which was partly attributable to pressure variability. Limiting the initial pressure ranges and avoiding large pressure fluctuations during initiation of PAP therapy may reduce early sleep disruption.</p>