Should we titrate positive end-expiratory pressure based on an end-expiratory transpulmonary pressure?

Abstract

Arguments continue to swirl regarding the need for and best method of positive end-expiratory pressure (PEEP) titration. An appropriately conducted decremental method that uses modest peak pressures for the recruiting maneuver (RM), a lung protective tidal excursion, relatively small PEEP increments and appropriate timing intervals is currently the most logical and attractive option, particularly when the esophageal balloon pressure (Pes) is used to calculate transpulmonary driving pressures relevant to the lung. The setting of PEEP by the Pes-guided end-expiratory pressure at the 'polarity transition' point of the transmural end-expiratory pressure is quite relevant to the locale of the esophageal balloon catheter. Its desirability, however, is limited by its tendency to encourage PEEP levels that are higher than most other PEEP titration methods. These Pes-set PEEP values promote higher mean airway pressures and are likely to be unnecessary when small tidal driving pressures are in use. Because high airway pressures increase global lung stress and risk hemodynamic compromise, the Pes-determined PEEP would seem associated with a relatively high hazard to benefit ratio for many patients.

Keywords: Recruitment; esophageal pressure; mechanical ventilation; open lung, transpulmonary pressure; positive end-expiratory pressure (PEEP); recruiting maneuver (RM).

Figure 1

Concept of transpulmonary pressure estimated by the esophageal balloon catheter. PEEP, positive end-expiratory pressure; FRC, functional residual capacity; Pes, esophageal pressure.

Figure 2

Modified staircase type of decremental positive end-expiratory pressure (PEEP) setting. The driving pressure used is similar to that used in practice and theoretically should be the transpulmonary value [∆(Palv-Pes)].

Figure 3

Left panel: an appropriately filled flaccid, high capacity balloon immersed in water collapses in the regions of higher hydrostatic forces and transmits to its lumen a pressure that reflects the lower pressures in its environment. Right panel: a well-placed esophageal balloon transmits pressure primarily from the luminal holes in a relatively caudal region that is free from artifact due to cardiac compression.