title: Pleural pressure and optimal positive end-expiratory pressure based on esophageal pressure versus chest wall elastance: incompatible results*.
abstract: OBJECTIVE
  1) To compare two published methods for estimating pleural pressure, one based on directly measured esophageal pressure and the other based on chest wall elastance. 2) To evaluate the agreement between two published positive end-expiratory pressure optimization strategies based on these methods, one targeting an end-expiratory esophageal pressure-based transpulmonary pressure of 0 cm H2O and the other targeting an end-inspiratory elastance-based transpulmonary pressure of 26 cm H2O.
  
  
  METHODS
  Retrospective study using clinical data.
  
  
  METHODS
  Medical and surgical ICUs.
  
  
  METHODS
  Sixty-four patients mechanically ventilated for acute respiratory failure with esophageal balloons placed for clinical management.
  
  
  METHODS
  Esophageal pressure and chest wall elastance-based methods for estimating pleural pressure and setting positive end-expiratory pressure were retrospectively applied to each of the 64 patients. In patients who were ventilated at two positive end-expiratory pressure levels, chest wall and respiratory system elastances were calculated at each positive end-expiratory pressure level.
  
  
  RESULTS
  The pleural pressure estimates using both methods were discordant and differed by as much as 10 cm H2O for a given patient. The two positive end-expiratory pressure optimization strategies recommended positive end-expiratory pressure changes in opposite directions in 33% of patients. The ideal positive end-expiratory pressure levels recommended by the two methods for each patient were discordant and uncorrelated (R = 0.05). Chest wall and respiratory system elastances grew with increases in positive end-expiratory pressure in patients with positive end-expiratory esophageal pressure-based transpulmonary pressures (p < 0.05).
  
  
  CONCLUSIONS
  Esophageal pressure and chest wall elastance-based methods for estimating pleural pressure do not yield similar results. The strategies of targeting an end-expiratory esophageal pressure-based transpulmonary pressure of 0 cm H2O and targeting an end-inspiratory elastance-based transpulmonary pressure of 26 cm H2O cannot be considered interchangeable. Finally, chest wall and respiratory system elastances may vary unpredictably with changes in positive end-expiratory pressure.
authors.affiliation: Department of Anesthesia, Critical Care and Pain Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA, USA.
authors.forename: Gaurav
authors.initials: G
authors.lastname: Gulati
authors.forename: Aileen
authors.initials: A
authors.lastname: Novero
authors.forename: Stephen H
authors.initials: SH
authors.lastname: Loring
authors.forename: Daniel
authors.initials: D
authors.lastname: Talmor
mesh_terms: D004947:Esophagus / Q000503:physiopathology*; D005260:Female; D006801:Humans; D007362:Intensive Care Units; D008168:Lung / Q000503:physiopathology*; D008170:Lung Compliance / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D011175:Positive-Pressure Respiration; D012131:Respiratory Insufficiency / Q000503:physiopathology / Q000628:therapy*; D012189:Retrospective Studies