Dynamics of lung collapse and recruitment during prolonged breathing in porcine lung injury.
Oleic acid (OA) injection, lung lavage, and endotoxin infusion are three commonly used methods to induce experimental lung injury. The dynamics of lung collapse and recruitment in these models have not been studied, although knowledge of this is desirable to establish ventilatory techniques that keep the lungs open. We measured lung density by computed tomography during breath-holding procedures. Lung injury was induced with OA, lung lavage, or endotoxin in groups of six mechanically ventilated pigs. After a stabilization period, repetitive computed tomography scans of the same slice were obtained during prolonged expirations with and without positive end-expiratory pressure and during prolonged inspirations after 5 and 30 s of expiration. Lung collapse and recruitment occurred mainly within the first 4 s of breath-holding procedures in all three lung injury models, and some collapse and recruitment occurred even within 0.6 s. OA-injured lungs were significantly more unstable than lungs injured by bronchoalveolar lavage or endotoxin infusion. In this experimental setting, expiration times <0.6 s are required to avoid cyclic alveolar collapse during mechanical ventilation without extrinsic positive end-expiratory pressure.
Department of Clinical Physiology, University of Uppsala, Uppsala 75185, Sweden.
P
P
Neumann
J E
JE
Berglund
E
E
Fernández Mondéjar
A
A
Magnusson
G
G
Hedenstierna
D000818:Animals; D001049:Apnea; D001794:Blood Pressure; D002302:Cardiac Output; D004731:Endotoxins / Q000633:toxicity; D004926:Escherichia coli; D006439:Hemodynamics / Q000502:physiology*; D008070:Lipopolysaccharides / Q000633:toxicity; D008168:Lung / Q000000981:diagnostic imaging / Q000503:physiopathology; D055370:Lung Injury; D019301:Oleic Acid / Q000633:toxicity; D010100:Oxygen / Q000097:blood; D011175:Positive-Pressure Respiration; D001261:Pulmonary Atelectasis / Q000503:physiopathology*; D011654:Pulmonary Edema / Q000139:chemically induced / Q000503:physiopathology*; D011669:Pulmonary Wedge Pressure; D015656:Respiratory Mechanics / Q000502:physiology*; D013552:Swine; D007507:Therapeutic Irrigation; D014057:Tomography, X-Ray Computed; D014655:Vascular Resistance
D004731:Endotoxins; D008070:Lipopolysaccharides; D019301:Oleic Acid; D010100:Oxygen