Auto-adjusting positive airway pressure: the fine line between engineering and medicine

Auto-adjusting positive airway pressure (APAP), unlike continuous PAP (CPAP), dynamically adjusts treatment pressure in response to events detected automatically from a derived flow signal. Introduced in the 90's, APAP quickly became a key tool in sleep clinics, initially serving as a faster alternative to manual titration for patients with obstructive sleep apnea (OSA), and later also as a long-term treatment option to expedite follow-up visits. APAP and CPAP are overall comparable in terms of adherence, efficacy and control of symptoms. However, concern remains that APAP offers less control of chronic health outcomes, such as blood pressure, kidney function and glycemic values. Other APAP-related challenges entail engineering aspects. A major issue is that APAP algorithms-which govern event detection/identification and pressure adjustments-are proprietary of and vary among manufacturers, making them poorly understood by clinicians. Furthermore, APAP algorithms do not always match-up well when compared to both manual titration or manually scored polysomnography, particularly in the presence of unintentional leak. Variability in event detection, leak compensation, and pressure adjustment algorithms among devices adds another layer of complexity to clinical decision-making. All this complicates the management of OSA patients, who could be left with substantial residual disordered breathing, high leak, and a wide pressure range.This review aims to bridge the gap between the clinical and engineering perspectives of APAP, providing an up-to-date overview of current knowledge and existing challenges that sleep clinicians should consider when managing OSA patients with PAP therapy.