Objectives: 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.
Design: Laboratory investigation.
Setting: Animal ICU of a governmental laboratory.
Subjects: Eleven awake, spontaneously breathing sheep on extracorporeal gas exchange.
Interventions: 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.
Measurements and Main 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.
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.
* See also p. 758.
This work was performed at the Comprehensive Intensive Care Research Task Area, US Army Institute of Surgical Research, Fort Sam Houston, TX.
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Supported, in part, by the Comprehensive Intensive Care Research Task Area, U.S. Army Institute of Surgical Research, Fort Sam Houston, TX.
Dr. Cannon received support for travel from Maquet Cardiovascular (funded travel to evaluate Cardiohelp in Wayne, NJ). Dr. Cannon’s institution received grant support from the Department of Defense (Defense Medical Research and Development Program Research Funding). Dr. Chung’s institution received grant support from the American Burn Association (grant to support multicenter study in septic shock in burns). Dr. Chung and his institution disclosed a patent: Burn decision support (Patent co-owned with Department of Defense). Dr. Cancio disclosed that this was government work. Dr. Gattinoni served as a board member for GRIFOLS, lectured for KCI, BBRAUN, BAXTER, and GRIFOLS (lectures and service on speakers bureau). Dr. Batchinsky served as board member for the Society for Complex Acute Illness and received support for travel from Maquet Cardiovascular. The opinions or assertions contained herein are the private views of the authors and are not to be construed as official or as reflecting the views of the Department of the Army or the Department of Defense. The remaining authors have disclosed that they do not have any potential conflicts of interest.
Address requests for reprints to: Thomas Langer, MD, Dipartimento di Fisiopatologia Medico-Chirurgica e dei Trapianti, Università degli Studi di Milano, Via F. Sforza 35, 20122 Milano, Italy. E-mail: firstname.lastname@example.org