• Takeshi Yoshida, AmatoMarcelo B PMBP4 Divisao de Pneumologia and., Domenico Luca Grieco, Lu Chen, Cristhiano A S Lima, Rollin Roldan, MoraisCaio C ACCA4 Divisao de Pneumologia and., Susimeire Gomes, CostaEduardo L VELV4 Divisao de Pneumologia and., Paulo F G Cardoso, Emmanuel Charbonney, RichardJean-Christophe MJM6 Cardiac Arrest and Ventilation International Association for Research, Laboratoire d'anatomie, Université du Québec à Trois-Rivières et Centre Intégré Universitaire de Santé et de Services Sociaux de la Mauricie-et-du-Centre-du, Laurent Brochard, and Brian P Kavanagh.
• 1 Keenan Research Centre, Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Ontario, Canada.
• Am. J. Respir. Crit. Care Med. 2018 Apr 15; 197 (8): 1018-1026.

RationaleEsophageal manometry is the clinically available method to estimate pleural pressure, thus enabling calculation of transpulmonary pressure (Pl). However, many concerns make it uncertain in which lung region esophageal manometry reflects local Pl.ObjectivesTo determine the accuracy of esophageal pressure (Pes) and in which regions esophageal manometry reflects pleural pressure (Ppl) and Pl; to assess whether lung stress in nondependent regions can be estimated at end-inspiration from Pl.MethodsIn lung-injured pigs (n = 6) and human cadavers (n = 3), Pes was measured across a range of positive end-expiratory pressure, together with directly measured Ppl in nondependent and dependent pleural regions. All measurements were obtained with minimal nonstressed volumes in the pleural sensors and esophageal balloons. Expiratory and inspiratory Pl was calculated by subtracting local Ppl or Pes from airway pressure; inspiratory Pl was also estimated by subtracting Ppl (calculated from chest wall and respiratory system elastance) from the airway plateau pressure.Measurements And Main ResultsIn pigs and human cadavers, expiratory and inspiratory Pl using Pes closely reflected values in dependent to middle lung (adjacent to the esophagus). Inspiratory Pl estimated from elastance ratio reflected the directly measured nondependent values.ConclusionsThese data support the use of esophageal manometry in acute respiratory distress syndrome. Assuming correct calibration, expiratory Pl derived from Pes reflects Pl in dependent to middle lung, where atelectasis usually predominates; inspiratory Pl estimated from elastance ratio may indicate the highest level of lung stress in nondependent "baby" lung, where it is vulnerable to ventilator-induced lung injury.

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