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Experimental and clinical studies have shown beneficial effects of recruitment maneuvers (RMs) (sustained inflation (SI) or SIGH) on ventilatory and gas exchange parameters. In this study we investigated the effect of different RMs on bacterial translocation from lung to blood.
Thirty-two rats were anesthetized, after tracheotomy was performed ventilation was started with 10 cmH2O Paw, 0 cmH2O PEEP, 60 breaths/minute, I/E: 1/2 on pressure-controlled ventilation (PCV) mode. After cannulation of the carotid artery was performed, a baseline blood gas sample was taken. Subsequently 0.5 ml of 105 cfu/ml Pseudomonas aeruginosa was inoculated through the tracheotomy tube and PEEP was increased to 3 cmH2O and ventilated for 30 minutes before randomization. Then rats were randomized into four groups: G1; SI was performed as 40 cmH2O PEEP and 0 Paw for 20 seconds, four times in an hour (15-minute intervals), G2; SI was performed as 20 cmH2O PEEP and 0 Paw for 40 seconds, four times in an hour (15-minute intervals), G3; SIGH was performed four times in 1 hour (15-minute intervals) as 40 cmH2O Paw, 3 mH2O PEEP for 60 seconds, G4; control group that was ventilated with Paw 10 cmH2O, PEEP 3cmH2O during the study period. Multiplication of pressure and pressure performing time for each study group were equal. Blood cultures were taken at baseline, 15 minutes after randomization, which is after each RM for the first hour, and last blood culture was taken after 60 minutes from the fourth RM. Then rats were sacrificed with intra-arterial sodium thiopental, and the lungs were extirpated; the left lung was taken for measurement of the wet weight/dry weight ratio (WW/DW).
There were no differences in baseline pH, PaO2, PaCO2, MAP, HR among groups. But PaO2 were decreased in groups G1, G2, and G3, but only in G3 was statistically significant to compared baseline values. The WW/DW ratio was found higher in G3 when compared with G1, and G2, but this difference was not significant. The amount of positive blood culture was higher in G3 at early study periods.
SIGH as a recruitment maneuver causes a high probability of bacterial translocation from the lung to the bloodstream.