Influence of mechanical ventilation on intestinal microcirculation and inflammation in septic rats

Introduction

Although the adverse effects of mechanical ventilation on circulation and intestinal organ perfusion are well known, the influence of assisted breathing versus controlled ventilation has not been investigated. We hypothesized that pressure support ventilation causes less decrease in gut perfusion and less neutrophil adhesion than controlled ventilation.

Methods

Male SD rats (n = 40) were anesthetized and tracheotomized and 10 animals each ventilated in pressure support (PSV) or pressure controlled (PCV) mode. PCV animals were paralyzed. After 5 hours of ventilation, intravital microscopy was performed. Endotoxin (15 mg/kg lipopolysaccharide) was given to 20 rats, 20 animals served as controls.

Results

There were no differences in baseline hemodynamics or gas exchange. Animals were stable over the whole observation period with minimal changes in blood pressure and oxygenation. In PCV, the percentage of functional capillaries in the longitudinal mucosal layer was lower (57 ± 39%) than in PSV (87 ± 33%). In sepsis, there was a further decrease in PCV and a major decrease in PSV. Leukocyte adhesion in the intestinal submocosal venules (for example, V1 venules) was higher in PCV (228 ± 119) than in PSV (93 ± 65) in controls, but not in septic animals.

Conclusions

In septic rats with preserved macrohemodynamic stability, intestinal perfusion was impaired after LPS infusion. Pressure-controlled ventilation had a significant influence on microcirculation and neutrophil adhesion in controls. In septic animals, pressure support ventilation did not attenuate these adverse effects as compared with PCV.