scholarly journals Regional Lung Derecruitment and Inflammation during 16 Hours of Mechanical Ventilation in Supine Healthy Sheep

2013 ◽  
Vol 119 (1) ◽  
pp. 156-165 ◽  
Author(s):  
Mauro R. Tucci ◽  
Eduardo L. V. Costa ◽  
Tyler J. Wellman ◽  
Guido Musch ◽  
Tilo Winkler ◽  
...  
Keyword(s):  
Mechanical Ventilation ◽  
Hypoxic Pulmonary Vasoconstriction ◽  
Regions Of Interest ◽  
Positive End Expiratory Pressure ◽  
18F Fluorodeoxyglucose ◽  
Positron Emission ◽  
Lung Dysfunction ◽  
Regional Lung ◽  
Net Uptake ◽  
Normal Lungs

Abstract Background: Lung derecruitment is common during general anesthesia. Mechanical ventilation with physiological tidal volumes could magnify derecruitment, and produce lung dysfunction and inflammation. The authors used positron emission tomography to study the process of derecruitment in normal lungs ventilated for 16 h and the corresponding changes in regional lung perfusion and inflammation. Methods: Six anesthetized supine sheep were ventilated with VT = 8 ml/kg and positive end-expiratory pressure = 0. Transmission scans were performed at 2-h intervals to assess regional aeration. Emission scans were acquired at baseline and after 16 h for the following tracers: (1) 18F-fluorodeoxyglucose to evaluate lung inflammation and (2) 13NN to calculate regional perfusion and shunt fraction. Results: Gas fraction decreased from baseline to 16 h in dorsal (0.31 ± 0.13 to 0.14 ± 0.12, P < 0.01), but not in ventral regions (0.61 ± 0.03 to 0.63 ± 0.07, P = nonsignificant), with time constants of 1.5–44.6 h. Although the vertical distribution of relative perfusion did not change from baseline to 16 h, shunt increased in dorsal regions (0.34 ± 0.23 to 0.63 ± 0.35, P < 0.01). The average pulmonary net 18F-fluorodeoxyglucose uptake rate in six regions of interest along the ventral–dorsal direction increased from 3.4 ± 1.4 at baseline to 4.1 ± 1.5⋅10−3/min after 16 h (P < 0.01), and the corresponding average regions of interest 18F-fluorodeoxyglucose phosphorylation rate increased from 2.0 ± 0.2 to 2.5 ± 0.2⋅10−2/min (P < 0.01). Conclusions: When normal lungs are mechanically ventilated without positive end-expiratory pressure, loss of aeration occurs continuously for several hours and is preferentially localized to dorsal regions. Progressive lung derecruitment was associated with increased regional shunt, implying an insufficient hypoxic pulmonary vasoconstriction. The increased pulmonary net uptake and phosphorylation rates of 18F-fluorodeoxyglucose suggest an incipient inflammation in these initially normal lungs.

Positive End-expiratory Pressure Redistributes Regional Blood Flow and Ventilation Differently in Supine and Prone Humans

2010 ◽  
Vol 113 (6) ◽  
pp. 1361-1369 ◽  
Author(s):  
Johan Petersson ◽  
Malin Ax ◽  
Joana Frey ◽  
Alejandro Sánchez-Crespo ◽  
Sten G. E. Lindahl ◽  
...  
Keyword(s):  
Mechanical Ventilation ◽  
Blood Flow ◽  
Single Photon ◽  
Regional Blood Flow ◽  
Photon Emission ◽  
Normal Subjects ◽  
Emission Computed Tomography ◽  
Positive End Expiratory Pressure ◽  
Regional Lung ◽  
Lung Blood Flow

Background Animal studies have demonstrated an interaction between posture and the effect of positive end-expiratory pressure (PEEP) on regional ventilation and lung blood flow. The aim of this study was to explore this interaction in humans. Methods Regional lung blood flow and ventilation were compared between mechanical ventilation with and without PEEP in the supine and prone postures. Six normal subjects were studied in each posture. Regional lung blood flow was marked with In-labeled macroaggregates and ventilation with Technegas (Tc). Radiotracer distributions were mapped using quantitative single-photon emission computed tomography. Results In supine subjects, PEEP caused a similar redistribution of both ventilation and blood flow toward dependent (dorsal) lung regions, resulting in little change in the V/Q correlation. In contrast, in prone subjects, the redistribution toward dependent (ventral) regions was much greater for blood flow than for ventilation, causing increased V/Q mismatch. Without PEEP, the vertical ventilation-to-perfusion gradient was less in prone postures than in supine, but with PEEP, the gradient was similar. Conclusions During mechanical ventilation of healthy volunteers, the addition of PEEP, 10 cm H2O, causes redistribution of both lung blood flow and ventilation, and the effect is different between the supine and prone postures. Our results suggest that the addition of PEEP in prone might be less beneficial than in supine and that optimal use of the prone posture requires reevaluation of the applied PEEP.

Early surfactant administration protects against lung dysfunction in a mouse model of ARDS

2003 ◽  
Vol 284 (5) ◽  
pp. L783-L790 ◽  
Author(s):  
Vijay P. A. Rasaiah ◽  
Jaret L. Malloy ◽  
James F. Lewis ◽  
Ruud A. W. Veldhuizen
Keyword(s):  
Mechanical Ventilation ◽  
Mouse Model ◽  
Protective Effect ◽  
Ex Vivo ◽  
Cecal Ligation ◽  
Exogenous Surfactant ◽  
Positive End Expiratory Pressure ◽  
Lung Dysfunction ◽  
Surfactant Administration ◽  
Significant Protective Effect

Sepsis can predispose the lung to insults such as mechanical ventilation (MV). It was hypothesized that treating the lung with exogenous surfactant early in the development of sepsis will reduce the lung dysfunction associated with MV 18 h later. Mice underwent sham or cecal ligation and perforation (CLP) surgery. Immediately after surgery, mice were either untreated or given 100 mg/kg of bovine lipid extract surfactant intratracheally. Eighteen hours later, the lungs were removed and analyzed either immediately or following ventilation ex vivo for 2 h by an “injurious” mode of ventilation (20 ml/kg, 0 cm positive end-expiratory pressure). In nonventilated lungs, exogenous surfactant had no impact on compliance or IL-6 concentrations in the lungs. In the ventilated groups, the administered surfactant had a significant protective effect on the lung dysfunction induced by MV, but only in the CLP lungs. We conclude that administration of exogenous surfactant at the time of a systemic insult can protect the lung from the damaging effects of MV 18 h later.

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