Comparison of live bacteria infusions in a porcine model of acute respiratory failure

Acute respiratory failure (ARF) related to sepsis continues to have a high mortality and uncertain pathogenesis. With a reproducible live Pseudomonas aeruginosa infusion pig model, the gas exchange, hemodynamics, and pulmonary clearance of this organism were compared with live Staphylococcus aureus and Escherichia coli. Lightly anesthetized, male, mixed-breed pigs, 15–30 kg, were intubated, allowed to breathe spontaneously, and had femoral artery, central venous, and Swan-Ganz catheterization through cutdowns. After baseline data were collected, approximately 1 × 10 9 organisms/20 kg/min were infused into a central vein for 4 hr with frequent monitoring of the variables. Immediate autopsies were done for related quantitative tissue culture studies. S. aureus pigs maintained a high rate of lung bacterial clearance with pulmonary hypertension, a nonsignificant decrease in P aO 2, and relatively normal lungs at autopsy. Ps. aeruginosa and E. coli animals developed systemic hypotension, pulmonary hypertension, increased pulmonary vascular resistance, hypoxemia, and decreased pulmonary clearance. Their lungs had gross congestion and edema. These studies confirm the suitability of E. coli and Ps. aeruginosa infusion into pigs as a model of sepsis-induced ARF in man. The findings also indicate that neither pulmonary hypertension nor bacterial clearance by the lungs is sufficient to cause ARF.