Identifying and Applying Best PEEP in Ventilated Critically Ill Patients

Positive end-expiratory pressure is an essential, life-saving component of the management of the acute respiratory distress syndrome (ARDS). After many years of experimental and clinical research, the best method to set PEEP is still debated. Typically, ARDS can be considered as having three compartments from non-dependent to dependent lung regions in a gravitational direction: aerated lung available for ventilation, recruitable lung, and non-recruitable lung. This chapter describes the different methods proposed to titrate PEEP at the bedside, and we discuss which ones may best assess this distribution. Compliance of the respiratory system has been frequently used but can be misleading in several situations. A mechanical assessment of the different compartment of the lungs seems necessary using either mechanical maneuvers to directly estimate lung recruitability or imaging techniques such as electrical impedance tomography or both. On top of this, the clinician must use a global integrated approach taking into account hemodynamics and gas exchange including CO2 elimination.