Rationale: Key pathophysiological traits or endotypes, that contribute to the development of obstructive sleep apnea (OSA) include an anatomically collapsible upper airway (UAC), a reduced dilator muscle responsiveness (MR), a reduced arousal threshold (AT) and an over-sensitive respiratory control system or loop gain (LG). Endotypes evaluation will permit to categorize OSA patient paving the way for a precision medicine. In Italy home respiratory polygraphy (HRP) are used for OSA routine evaluation. The aim of this research was to simply and indirectly evaluate OSA endotype from HRP reports.

Methods: This was a retrospective analysis of HRP reports using an ad-hoc software to extrapolate OSA endotypes. We analyzed reports of routine HRP performed at two Institutes in Milano and in Monza-Brianza between 2014 and 2022 including only HRP with an apnea-hypopnea index (AHI)?5/h. The software automatically categorized each HRP as having: a) high UAC if obstructive events>90%, if the AHI > 40/h and if the CPAP pressure > 8; b) high LG if central events > 20%, if there was periodic breathing and if there weren?t REM-related events; c) low AT if AHI<30/h, desaturation nadir >82% and the ratio hypopneas\apneas > 58.3%. MR was not evaluated.

Results: HRP?s reports of 9068 patients were studied. 72% were males, the median [Q1-Q3] age was 60 [50-71] years and the BMI was 28 [25-32] kg\m2. Regarding endotypes: 9% presented a high UAC, 62% a low AT and 33% a high LG.

Conclusions: OSA main endotype in our population was AT. We propose a simple method to automatically evaluate UAC, LG and AT from HRP?s reports, that could be applied in the routine clinical practice of sleep specialists helping to a future personalized OSA therapy.