Objective: To determine the effect of peak inspiratory pressure (PIP) and positive end-expiratory pressure (PEEP) on the development of bacteremia with Klebsiella pneumoniae after mechanical ventilation of intratracheally inoculated rats.
Design: Prospective, randomized, animal study.
Setting: Experimental intensive care unit of a University.
Subjects: Eighty male Sprague Daw-ley rats.
Interventions: Intratracheal inoculation with 100 µl of saline containing 3.5−5.0×105 colony forming units (CFUs) K. pneumoniae/ml. Pressure-controlled ventilation (frequency 30 bpm; I/E ratio=1:2; FIO2=1.0) for 180 min at the following settings (PIP/PEEP in cmH2O): 13/3 (n=16); 13/0 (n=16); 30/10 (n=16) and 30/0 (n=16), starting 22 h after inoculation. Arterial blood samples were obtained and cultured before and 180 min after mechanical ventilation and immediately before sacrifice in two groups of non-ventilated control animals (n=8 per group). After sacrifice, the lungs were homogenized to determine the number of CFUs K. pneumoniae.
Measurements and results: The number of CFUs recovered from the lungs was comparable in all experimental groups. After 180 min, 11 animals had positive blood cultures for K. pneumoniae in group 30/0, whereas only 2,0 and 2 animals were positive in 13/3,13/0 and 30/10, respectively (p<0.05 group 30/0 versus all other groups).
Conclusions: These data show that 3 h of mechanical ventilation with a PIP of 30 cmH2O without PEEP in rats promotes bacteremia with K. pneumoniae. The use of 10 cmH2O PEEP at such PIP reduces ventilation-induced K. pneumoniae bacteremia.
K. pneumoniaeBacteremia Mechanical ventilation Blood gases Animal Rat
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