OSA phatophysiological traits in Milan and Monza-Brianza

<b>Rationale:</b> 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. <b>Methods:</b> 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&gt;90%, if the AHI &gt; 40/h and if the CPAP pressure &gt; 8; b) high LG if central events &gt; 20%, if there was periodic breathing and if there weren’t REM-related events; c) low AT if AHI&lt;30/h, desaturation nadir &gt;82% and the ratio hypopneas\apneas &gt; 58.3%. MR was not evaluated. <b>Results:</b> 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. <b>Conclusions:</b> 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.