An alternative method for determining transpulmonary pressure and optimal positive endexpiratory pressure (PEEP) through a simple PEEP step procedure

• Applicant: Professor Dr. Onnen Mörer
• Subject Area: Anaesthesiology
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 550341680

Acute Respiratory Distress Syndrome (ARDS) is a major cause of mortality and morbidity in critically ill patients. Lung-protective ventilation strategies with low tidal volumes and limited ventilatory pressures as well as appropriate setting of positive end-expiratory pressure (PEEP) can positively influence outcome. PEEP can be used to reopen the unventilated alveoli and to relieve hypoxaemia. On the other hand, high PEEP and thus high transpulmonary pressure increases the risk of over-distension of the lung tissue, causes ventilator induced lung injury and increases mortality. Therefore, it is necessary to find an individual PEEP level that reaches an optimal compromise (avoiding collapse and alveolar cycling, ensure oxygenation decreasing mechanical stress). The PEEP-approach most widely used (ARDSnet PEEP-Table) estimates the necessary PEEP as a function of the required FiO2 to reach a target partial pressure of oxygen (PaO2). However, this method does not consider individual respiratory mechanics. Alternatively PEEP settings can be based on individual respiratory mechanics (e.g. titrating the best respiratory compliance during an incremental or decremental PEEP-Trial). Unfortunately, studies that clearly demonstrate the advantage of a method are lacking and recent international guidelines were unable provide a clear recommendation for a PEEP titration strategy. This means that there is a relevant need for clinical research. The transpulmonary pressure (airway pressure minus esophageal pressure as surrogate for intrapleural pressure) is the effective pressure that expands the lungs during inspiration and prevents lung collapse during expiration. Talmor and colleagues were the first to develop a protocol where PEEP settings were based on a target end-expiratory transpulmonary pressure. Although there are conflicting results, resent data suggests an outcome benefit if the target transpulmonary end-expiratory pressure is kept within narrow limits. Recently a non-invasive method for PEEP titration has been suggested based on the assumption that the change in end-expiratory transpulmonary pressure (ΔPLEE) following a PEEP increase is caused by the PEEP induced increase in end-expiratory lung volume (ΔEELV). The increase in EELV is determined by the size of the PEEP step and the elastic properties of the lung (alone) as ΔPEEP/EL and end-expiratory transpulmonary pressure increases as much as PEEP is increased. This alternative approach of diagnosing the lung elastic properties and finding the PEEP level with the lowest transpulmonary driving pressure by PEEP-steps procedure offers a new perspective being less invasive and easier to apply in the ICU-setting. With the proposed trial we aim at testing if the new PEEP Step method can determine the same transpulmonary pressures as the esophageal pressure measurement based method and if it allows PEEP adjustments comparable to the standard approaches while avoiding alveolar hyperinflation.

• DFG Programme: Clinical Trials