title: Extracorporeal gas exchange and spontaneous breathing for the treatment of acute respiratory distress syndrome: an alternative to mechanical ventilation?*.
abstract: OBJECTIVE
  Venovenous extracorporeal gas exchange is increasingly used in awake, spontaneously breathing patients as a bridge to lung transplantation. Limited data are available on a similar use of extracorporeal gas exchange in patients with acute respiratory distress syndrome. The aim of this study was to investigate the use of extracorporeal gas exchange in awake, spontaneously breathing sheep with healthy lungs and with acute respiratory distress syndrome and describe the interactions between the native lung (healthy and diseased) and the artificial lung (extracorporeal gas exchange) in this setting.
  
  
  METHODS
  Laboratory investigation.
  
  
  METHODS
  Animal ICU of a governmental laboratory.
  
  
  METHODS
  Eleven awake, spontaneously breathing sheep on extracorporeal gas exchange.
  
  
  METHODS
  Sheep were studied before (healthy lungs) and after the induction of acute respiratory distress syndrome via IV injection of oleic acid. Six gas flow settings (1-10 L/min), resulting in different amounts of extracorporeal CO2 removal (20-100% of total CO2 production), were tested in each animal before and after the injury.
  
  
  RESULTS
  Respiratory variables and gas exchange were measured for every gas flow setting. Both healthy and injured sheep reduced minute ventilation according to the amount of extracorporeal CO2 removal, up to complete apnea. However, compared with healthy sheep, sheep with acute respiratory distress syndrome presented significantly increased esophageal pressure variations (25 ± 9 vs 6 ± 3 cm H2O; p < 0.001), which could be reduced only with very high amounts of CO2 removal (> 80% of total CO2 production).
  
  
  CONCLUSIONS
  Spontaneous ventilation of both healthy sheep and sheep with acute respiratory distress syndrome can be controlled via extracorporeal gas exchange. If this holds true in humans, extracorporeal gas exchange could be used in awake, spontaneously breathing patients with acute respiratory distress syndrome to support gas exchange. A deeper understanding of the pathophysiology of spontaneous breathing during acute respiratory distress syndrome is however warranted in order to be able to propose extracorporeal gas exchange as a safe and valuable alternative to mechanical ventilation for the treatment of patients with acute respiratory distress syndrome.
authors.affiliation: 1Comprehensive Intensive Care Research Task Area, United States Army Institute of Surgical Research, Fort Sam Houston, San Antonio, TX. 2Dipartimento di Fisiopatologia Medico-Chirurgica e dei Trapianti, Università degli Studi di Milano, Milan, Italy. 3National Research Council, National Academies, Washington, DC. 4School of Medicine, Università degli Studi di Milano, Milan, Italy. 5Department of Surgery, San Antonio Military Medical Center, San Antonio, TX. 6Uniformed Services University of the Health Sciences, Bethesda, MD. 7Dipartimento di Anestesia, Rianimazione (Intensiva e Sub-intensiva) e Terapia del Dolore, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico di Milano, Milan, Italy.
authors.forename: Thomas
authors.initials: T
authors.lastname: Langer
authors.forename: Vittoria
authors.initials: V
authors.lastname: Vecchi
authors.forename: Slava M
authors.initials: SM
authors.lastname: Belenkiy
authors.forename: Jeremy W
authors.initials: JW
authors.lastname: Cannon
authors.forename: Kevin K
authors.initials: KK
authors.lastname: Chung
authors.forename: Leopoldo C
authors.initials: LC
authors.lastname: Cancio
authors.forename: Luciano
authors.initials: L
authors.lastname: Gattinoni
authors.forename: Andriy I
authors.initials: AI
authors.lastname: Batchinsky
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D004195:Disease Models, Animal; D015199:Extracorporeal Membrane Oxygenation / Q000379:methods* / Q000401:mortality; D005260:Female; D016014:Linear Models; D011659:Pulmonary Gas Exchange; D011897:Random Allocation; D020127:Recovery of Function / Q000502:physiology; D012016:Reference Values; D012119:Respiration; D012121:Respiration, Artificial / Q000379:methods* / Q000401:mortality; D012128:Respiratory Distress Syndrome / Q000175:diagnosis / Q000401:mortality* / Q000628:therapy*; D018570:Risk Assessment; D012720:Severity of Illness Index; D012756:Sheep; D015996:Survival Rate