title: Dynamics of end expiratory lung volume after changing positive end-expiratory pressure in acute respiratory distress syndrome patients.
abstract: BACKGROUND
  Lung recruitment maneuvers followed by an individually titrated positive end-expiratory pressure (PEEP) are the key components of the open lung ventilation strategy in acute respiratory distress syndrome (ARDS). The staircase recruitment maneuver is a step-by-step increase in PEEP followed by a decremental PEEP trial. The duration of each step is usually 2 minutes without physiologic rationale.
  
  
  METHODS
  In this prospective study, we measured the dynamic end-expiratory lung volume changes (ΔEELV) during an increase and decrease in PEEP to determine the optimal duration for each step. PEEP was progressively increased from 5 to 40 cmH2O and then decreased from 40 to 5 cmH2O in steps of 5 cmH2O every 2.5 minutes. The dynamic of ΔEELV was measured by direct spirometry as the difference between inspiratory and expiratory tidal volumes over 2.5 minutes following each increase and decrease in PEEP. ΔEELV was separated between the expected increased volume, calculated as the product of the respiratory system compliance by the change in PEEP, and the additional volume.
  
  
  RESULTS
  Twenty-six early onset moderate or severe ARDS patients were included. Data are expressed as median [25th-75th quartiles]. During the increase in PEEP, the expected increased volume was achieved within 2[2-2] breaths. During the decrease in PEEP, the expected decreased volume was achieved within 1 [1-1] breath, and 95 % of the additional decreased volume was achieved within 8 [2-15] breaths. Completion of volume changes in 99 % of both increase and decrease in PEEP events required 29 breaths.
  
  
  CONCLUSIONS
  In early ARDS, most of the ΔEELV occurs within the first minute, and change is completed within 2 minutes, following an increase or decrease in PEEP.
authors.affiliation: Service de réanimation polyvalente, Hôpital Sainte Musse, 54 Avenue Henri Sainte Claire Deville, 83056, Toulon, France. aude.garnero@gmail.com.|Australian and New Zealand Intensive Care Research Centre, Department of Epidemiology and Preventive Medicine, Monash University, The Alfred Centre, 99 Commercial Road, Melbourne, VIC, 3004, Australia. aude.garnero@gmail.com.
authors.forename: Aude
authors.initials: A
authors.lastname: Garnero
authors.affiliation: Department of Intensive Care and Hyperbaric Medicine, Alfred Hospital, 55 Commercial Road, PO Box 315, Prahan, VIC, 3181, Australia. dtuxen1@bigpond.com.
authors.forename: David
authors.initials: D
authors.lastname: Tuxen
authors.affiliation: Service de réanimation polyvalente, Hôpital Sainte Musse, 54 Avenue Henri Sainte Claire Deville, 83056, Toulon, France. gaelle.corno@ch-toulon.fr.
authors.forename: Gaëlle
authors.initials: G
authors.lastname: Corno
authors.affiliation: Service de réanimation polyvalente, Hôpital Sainte Musse, 54 Avenue Henri Sainte Claire Deville, 83056, Toulon, France. jacques.durand-gasselin@ch-toulon.fr.
authors.forename: Jacques
authors.initials: J
authors.lastname: Durand-Gasselin
authors.affiliation: Australian and New Zealand Intensive Care Research Centre, Department of Epidemiology and Preventive Medicine, Monash University, The Alfred Centre, 99 Commercial Road, Melbourne, VIC, 3004, Australia. carol.hodgson@monash.edu.
authors.forename: Carol
authors.initials: C
authors.lastname: Hodgson
authors.affiliation: Service de réanimation polyvalente, Hôpital Sainte Musse, 54 Avenue Henri Sainte Claire Deville, 83056, Toulon, France. jean-michel@arnal.org.|Medical Research, Hamilton Medical, 8 Via Crusch, 7402, Bonaduz, Switzerland. jean-michel@arnal.org.
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Arnal
mesh_terms: D000368:Aged; D005260:Female; D006801:Humans; D008168:Lung / Q000503:physiopathology; D008176:Lung Volume Measurements; D008297:Male; D011175:Positive-Pressure Respiration / Q000379:methods; D011446:Prospective Studies; D012128:Respiratory Distress Syndrome / Q000503:physiopathology / Q000628:therapy*; D013997:Time Factors