989: Palicc-2 and Berlin Perform Similarly in a Cohort of Adolescents and Young Adults With Ards

Introduction: Pediatric (PALICC-2) and adult (Berlin) acute respiratory distress syndrome (ARDS) guidelines differ, leaving uncertainty for the diagnosis and management of ARDS in adolescents and young adults (AYA). We sought to evaluate both definitions in this population admitted to pediatric and adult ICUs with ARDS. Methods: This is a retrospective cohort study of AYAs aged 15-25 years admitted to the ICU in a pediatric hospital or two adult hospitals from 2023 through 2025. Intubated AYAs were evaluated for meeting PALICC-2 and Berlin definitions of ARDS. Markers of oxygenation for ARDS severity in the 3 days after diagnosis were obtained. Examined outcomes include mortality, duration of mechanical ventilation and length of stay. Results: One hundred ninety-two AYAs were included with 91 (47%) admitted to the pediatric ICU and 101 (53%) to adult ICUs. All patients met PALICC-2 criteria and 109 (57%) met Berlin criteria. When SpO2:FiO2 was used, 171 (89%) met modified Berlin criteria. Over the course of 72 hours post-ARDS diagnosis, 139 (72%) eventually met Berlin criteria and 173 (90%) met modified Berlin criteria. At diagnosis severe ARDS was present in 107 (56%) by PALICC-2, 47 (25%) by traditional Berlin, and 116 (60%) by modified Berlin criteria. Mortality was similar regardless of ARDS definition used and remained similar for severe ARDS across definition groups. There was no difference in the ability to discriminate mortality based on severity of ARDS in PALICC-2 or Berlin at diagnosis: PALICC-2 AUC=0.55 (95% CI 0.46-0.64) vs Berlin AUC=0.51 (95% CI 0.44-0.58), p=0.39. There was no difference in duration of mechanical ventilation (6 [IQR:3,11] vs. 8 [IQR:4,12] days), ventilator free days at 28 days (19 [IQR:0,24] vs. 17 [IQR:0,22] days), length of ICU stay (10 [IQR:5,19] vs. 12 [IQR:6,20] days) or hospital length of stay (19 [IQR:9,31] vs. 21 [IQR:11,33] days) using PALICC-2 or Berlin, respectively. Conclusions: All AYAs in this cohort met PALICC-2 criteria at ARDS onset, while 90% of patients eventually met Berlin or modified Berlin criteria within 3 days of onset. Though PALICC-2 captured more patients and diagnosed them sooner, there were no differences in clinical outcomes between definitions. There remains uncertainty whether one criterion may perform better in this age group.