Positive end-expiratory pressure (PEEP) is routinely utilized during mechanical ventilation to improve alveolar recruitment and combat cyclic trauma from repeated deflation/expansion of the alveolar unit which can lead to stimulate the inflammatory cascade (“atelectrauma”). As a cardiac anesthesiologist, most of my patients’ respiratory mechanics are affected during and immediately after sternotomies and thoracotomies due to changes in their chest wall compliance, lung resection, opening the pleural space, chest tubes on suction, etc. As an intensivist, I’m faced with different challenges ventilating patients with advanced pulmonary fibrosis, acute respiratory distress syndrome (ARDS), etc. One point of debate in both settings is how much PEEP is “just right” for each patient.
PEEP is often titrated based on FiO2 (ARDSnet), driving pressures, pressure-volume loop inflexions, and esophageal balloons (estimates intrapleural pressure to determine transpulmonary pressure). For heterogeneous pathologies like ARDS, my colleagues and I tend to agree with low tidal volume practices (~6 cc/kg of ideal body weight), low driving pressures (ratio of tidal volume to static compliance), and low FiO2; however the PEEP we dial in often varies considerably. Even “best PEEP trials” are confounded by the fact that many intraoperative and ICU pulmonary states evolve change based on things like abdominal insufflation, one lung ventilation, evolving infection/ARDS, growing extrapulmonary fluid collections, etc. In the OR cases I’m involved with, the “best PEEP” will change often over the course of a single case!
In general, I start with low tidal volume ventilation using a pressure-regulated, volume control mode tweaking PEEP and monitoring mean airway pressures till I reach a minimal driving pressure with acceptable ventilation (sometimes requiring permissive hypercapnea).
What do you consider when determining PEEP requirements? I’m especially curious to hear opinions from respiratory therapists and intensivists about how they approach this topic, so drop me a comment below! 🙂
