Flow-controlled expiration: a novel ventilation mode to attenuate experimental porcine lung injury.
BACKGROUND
Whereas the effects of various inspiratory ventilatory modifications in lung injury have extensively been studied, those of expiratory ventilatory modifications are less well known. We hypothesized that the newly developed flow-controlled expiration (FLEX) mode provides a means of attenuating experimental lung injury.


METHODS
Experimental acute respiratory distress syndrome was induced by i.v. injection of oleic acid in 15 anaesthetized and mechanically ventilated pigs. After established lung injury ([Formula: see text]ratio <27 kPa), animals were randomized to either a control group receiving volume-controlled ventilation (VCV) or a treatment group receiving VCV with additional FLEX (VCV+FLEX). At predefined times, lung mechanics and oxygenation were assessed. At the end of the experiment, the pigs were killed, and bronchoalveolar fluid and lung biopsies were taken. Expression of inflammatory cytokines was analysed in lung tissue and bronchoalveolar fluid. Lung injury score was determined on the basis of stained tissue samples.


RESULTS
Compared with the control group (VCV; n=8), the VCV+FLEX group (n=7) demonstrated greater dynamic lung compliance and required less PEEP at comparable [Formula: see text] (both P<0.05), had lower regional lung wet-to-dry ratios and lung injury scores (both P<0.001), and showed less thickening of alveolar walls (an indicator of interstitial oedema) and de novo migration of macrophages into lung tissue (both P<0.001).


CONCLUSIONS
The newly developed FLEX mode is able to attenuate experimental lung injury. FLEX could provide a novel means of lung-protective ventilation.
Division for Experimental Anaesthesiology, Department of Anaesthesiology, University Medical Centre Freiburg, Freiburg, Germany.
U
U
Goebel
Experimental Surgery, CEMT-FR, University Medical Centre Freiburg, Freiburg, Germany.
J
J
Haberstroh
Department of Cardiovascular Surgery, University Medical Centre Freiburg, Freiburg, Germany.
K
K
Foerster
Division for Experimental Anaesthesiology, Department of Anaesthesiology, University Medical Centre Freiburg, Freiburg, Germany.
C
C
Dassow
Division for Experimental Anaesthesiology, Department of Anaesthesiology, University Medical Centre Freiburg, Freiburg, Germany.
H-J
HJ
Priebe
Division for Experimental Anaesthesiology, Department of Anaesthesiology, University Medical Centre Freiburg, Freiburg, Germany.
J
J
Guttmann
Division for Experimental Anaesthesiology, Department of Anaesthesiology, University Medical Centre Freiburg, Freiburg, Germany stefan.schumann@uniklinik-freiburg.de.
S
S
Schumann
D000818:Animals; D001706:Biopsy; D001992:Bronchoalveolar Lavage Fluid; D016207:Cytokines / Q000378:metabolism; D004195:Disease Models, Animal; D045853:Exhalation / Q000502:physiology*; D005260:Female; D008168:Lung / Q000378:metabolism / Q000473:pathology; D008170:Lung Compliance / Q000502:physiology; D055370:Lung Injury / Q000209:etiology / Q000378:metabolism / Q000503:physiopathology* / Q000517:prevention & control*; D008297:Male; D019301:Oleic Acid; D011175:Positive-Pressure Respiration / Q000379:methods; D011650:Pulmonary Alveoli / Q000378:metabolism / Q000473:pathology; D011659:Pulmonary Gas Exchange / Q000502:physiology; D012121:Respiration, Artificial / Q000009:adverse effects / Q000379:methods*; D012128:Respiratory Distress Syndrome / Q000139:chemically induced / Q000473:pathology / Q000503:physiopathology* / Q000628:therapy*; D012720:Severity of Illness Index; D013552:Swine
D016207:Cytokines; D019301:Oleic Acid
acute respiratory distress syndrome; oleic acid; positive pressure ventilation; pulmonary oedema