B80-1-17 Airway Opening Pressure and End-Expiratory Transpulmonary Pressure in an Obese Patient: Two Sides of the Same Coin?

Abstract Rationale Preventing ventilation-induced lung injury (VILI) during mechanical ventilation improves survival. Individualized positive end-expiratory pressure (PEEP) titration can optimize lung mechanics and gas exchange. PEEP requirements can be assessed by different techniques. These include analysis of pressure-time curves to identify critical airway opening pressure (AOP) or measurement of transpulmonary pressure via an esophageal catheter, each with distinct physiological bases. We present a clinical case where both methods were used concurrently, highlighting their correlation and potential clinical implications. Methods We simultaneously applied both PEEP titration methods in a 58-year-old morbidly obese patient (BMI 45 kg/m²) who developed severe oxygenation impairment from hydrostatic pulmonary edema following emergent repair of a ruptured abdominal aortic aneurysm. AOP was determined using a low-flow inflation maneuver (5 L/min, 5 breaths/min, PEEP 5 cmH2O) by identifying the lower inflection point on the airway pressure-time curve. Concurrently, end-expiratory transpulmonary pressure was measured via an esophageal balloon catheter to guide PEEP. Results PEEP levels below the identified AOP resulted in a negative end-expiratory transpulmonary pressure, indicating airway closure and atelectasis. In contrast, at PEEP levels at or above AOP, end-expiratory transpulmonary pressure remained positive, signifying alveolar patency and reduced risk of collapse. This relationship was observed consistently at multiple time points, demonstrating a strong correlation between the AOP and transpulmonary pressure measurements. Conclusions In this case, titrating PEEP to the AOP maintained a positive end-expiratory transpulmonary pressure. This finding suggests that both the low-flow pressure curve and esophageal manometry methods can identify adequate PEEP to avoid alveolar collapse. These approaches may converge when chest wall mechanics are near normal and airway pressure curves accurately reflect transpulmonary pressure. Identifying the AOP pinpoints the threshold for alveolar recruitment (the lower inflection point), while esophageal manometry provides insight into pleural pressure and lung-chest wall mechanics. Due to hysteresis, AOP is typically higher than the critical closing pressure, but it offers a practical estimate of the minimum PEEP needed to prevent end-expiratory collapse. Regular assessment of AOP and using it as a PEEP target could help minimize derecruitment in settings where esophageal pressure monitoring is not available. However, this maneuver reflects global respiratory mechanics and may be less accurate in the presence of significant regional lung disease. This case highlights the potential of AOP as a surrogate for transpulmonary pressure-guided PEEP titration in resource-limited scenarios. It also underscores the need for further investigation to validate this strategy. This abstract is funded by: N/A