title: Gas exchange and lung mechanics in patients with acute respiratory distress syndrome: comparison of three different strategies of positive end expiratory pressure selection.
abstract: OBJECTIVE
  The purpose of the study was to compare gas exchange and lung mechanics between different strategies to select positive end-expiratory pressure (PEEP) in acute respiratory distress syndrome (ARDS).
  
  
  METHODS
  In 20 consecutive ARDS patients, 3 PEEP selection strategies were evaluated. One strategy was based on oxygenation using the ARDS network PEEP/fraction of inspired oxygen (Fio2) table; and two were based on lung mechanics, either PEEP titrated to reach a plateau pressure of 28 to 30 cm H2O as in the ExPress trial or best respiratory compliance method during a derecruitment maneuver. Gas exchange, airway pressures, stress index (SI), and end-expiratory transpulmonary pressure (P(tpe)) and end-inspiratory transpulmonary pressure (P(tpi)) values were assessed. Data are expressed as median (interquartile range [IQR]).
  
  
  RESULTS
  Lower total PEEP levels were observed with the use of the PEEP/Fio2 table (8.7 [6-10] cm H2O); intermediate PEEP levels, with the Best Compliance approach (13.0 [10.2-13.8] cm H2O); and higher PEEP levels, with the ExPress strategy (16.5 [15.0-18.5] cm H2O) (P < .01). Pao2/Fio2 ratio was lower with the PEEP/Fio2 table. Oxygenation with Best Compliance approach and ExPress strategy was not different with lower plateau pressure in the former (23 [20-25] vs 30 [29-30] cm H2O; P < .01). Paco2 was slightly higher with the ExPress method than the others 2 strategies. Negative P(tpe) was observed in 35% of the patients with the PEEP/Fio2 table, in 15% applying the Best Compliance, and in only 1 case with the ExPress method. Higher SI and P(tpi), with lower lung compliance, were obtained with ExPress strategy.
  
  
  CONCLUSIONS
  Using a best respiratory compliance approach resulted in better oxygenation levels without risk of overdistension according to SI and P(tpi), achieving a mild risk of lung collapse according to P(tpe).
authors.affiliation: Intensive Care Unit, Department of Medicine Instituto Universitario "Centro de Educación Médica e Investigaciones Clínicas" (CEMIC), Buenos Aires, Argentina. Electronic address: rvalentini@cemic.edu.ar.
authors.forename: Ricardo
authors.initials: R
authors.lastname: Valentini
authors.affiliation: Intensive Care Unit, Department of Medicine Instituto Universitario "Centro de Educación Médica e Investigaciones Clínicas" (CEMIC), Buenos Aires, Argentina.
authors.forename: José
authors.initials: J
authors.lastname: Aquino-Esperanza
authors.affiliation: Intensive Care Unit, Department of Medicine Instituto Universitario "Centro de Educación Médica e Investigaciones Clínicas" (CEMIC), Buenos Aires, Argentina.
authors.forename: Ignacio
authors.initials: I
authors.lastname: Bonelli
authors.affiliation: Intensive Care Unit, Department of Medicine Instituto Universitario "Centro de Educación Médica e Investigaciones Clínicas" (CEMIC), Buenos Aires, Argentina.
authors.forename: Patricio
authors.initials: P
authors.lastname: Maskin
authors.affiliation: Intensive Care Unit, Department of Medicine Instituto Universitario "Centro de Educación Médica e Investigaciones Clínicas" (CEMIC), Buenos Aires, Argentina.
authors.forename: Mariano
authors.initials: M
authors.lastname: Setten
authors.affiliation: Intensive Care Unit, Department of Medicine Instituto Universitario "Centro de Educación Médica e Investigaciones Clínicas" (CEMIC), Buenos Aires, Argentina.
authors.forename: Florencia
authors.initials: F
authors.lastname: Danze
authors.affiliation: Intensive Care Unit, Department of Medicine Instituto Universitario "Centro de Educación Médica e Investigaciones Clínicas" (CEMIC), Buenos Aires, Argentina.
authors.forename: Shiry
authors.initials: S
authors.lastname: Attie
authors.affiliation: Intensive Care Unit, Department of Medicine Instituto Universitario "Centro de Educación Médica e Investigaciones Clínicas" (CEMIC), Buenos Aires, Argentina.
authors.forename: Pablo O
authors.initials: PO
authors.lastname: Rodriguez
mesh_terms: D000368:Aged; D001784:Blood Gas Analysis; D005260:Female; D006801:Humans; D008168:Lung / Q000503:physiopathology*; D008170:Lung Compliance / Q000502:physiology; D008297:Male; D008875:Middle Aged; D011175:Positive-Pressure Respiration / Q000379:methods*; D011312:Pressure; D011659:Pulmonary Gas Exchange / Q000502:physiology*; D012128:Respiratory Distress Syndrome / Q000503:physiopathology / Q000628:therapy*; D015656:Respiratory Mechanics / Q000502:physiology*
keywords: ARDS; Lung mechanics; Mechanical ventilation; PEEP selection; Transpulmonary pressure