Relationship between PALM Scale endotypes and surgical outcomes in Maxillomandibular Advancement for Obstructive Sleep Apnea: the AOUP experience.

Obstructive Sleep Apnea Syndrome (OSAS) is a respiratory disorder characterized by recurrent upper airway obstructions, significantly impacting health. The PALM scale is a classification system for obstructive sleep apnea (OSA) that focuses on pathophysiological traits, stratifying patients based on four primary determinants of airway collapsibility and ventilatory control, which influence the severity and treatment response of OSA. The PALM classification helps tailor therapeutic strategies beyond anatomical considerations, guiding personalized approaches such as PAP therapy, myofunctional therapy, surgical interventions, or pharmacological treatments, based on the dominant trait of each patient. While it offers a personalized approach to OSAS treatment, its impact on bimaxillary advancement surgery outcomes has not been fully explored. Study Objective - The objective of this study was to investigate the potential relationship between the post-operative AHI (Apnea-Hypopnea Index) following bimaxillary advancement surgery and the PALM classification. Specifically, we aimed to evaluate whether different PALM phenotypes could predict surgical outcomes in patients with OSA. This study assessed the effectiveness of surgical treatment in patients classified as PALM 1 and PALM 2, analyzing results in percentage terms to eliminate the influence of baseline Apnea-Hypopnea Index (AHI) values. Materials and Methods - The study included 59 patients (55 males and 4 females) aged between 24 and 72 years, with a BMI ranging from 18.9 to 36. Patients were selected based on the evaluation of their preoperative AHI index (pre-AHI) and the CPAP therapeutic pressure to which they were subjected prior to bimaxillary advancement surgery. Patients who had never undergone CPAP therapy before surgery were excluded. The PALM score was then assigned, considering that patients with AHI > 40 and CPAP > 6 cmH2O were classified as PALM 1; AHI < 40 but CPAP > 6 were classified as PALM 2, and patients with AHI < 40 and CPAP < 6 were classified as PALM 3. Results - Based on this classification, 43 patients were included in the PALM 1 group and 16 in the PALM 2 group. The collected data were analyzed using an independent T-test to assess the statistical significance of the percentage reduction in AHI. Subsequently, chi-square tests were used to observe the distribution of patients, setting the healing threshold for AHI first at 15, then at 10, and finally at 5. The results show a statistically significant reduction in AHI in both groups, with a particularly marked improvement in PALM 1 patients (p<0.0001), who had a higher baseline AHI compared to PALM 2 patients. The analysis of pre- and post-treatment AHI reveals a significant reduction within each group. Furthermore, using a cutoff of 5, which represents true post-treatment recovery, a significantly higher frequency of fully recovered patients was observed in the PALM 1 group compared to the PALM 2 group (44.19% vs. 12.50%), with statistical significance. Discussion and Conclusions - The PALM classification system is useful for guiding therapeutic decisions in Obstructive Sleep Apnea Syndrome (OSAS). Our study suggests that a personalized therapeutic approach, tailored to each patient's PALM phenotype, may lead to optimized outcomes. This implies that by considering specific physiological traits of each patient, such as airway collapsibility, arousal threshold, ventilatory control, and muscle responsiveness, more effective and targeted treatment plans can be developed. However, further studies with a larger and more diverse patient cohort are needed to confirm these preliminary results. Such preliminary findings support the idea that a deeper understanding of these pathophysiological traits may improve the success of proposed treatments for patients with OSAS.