Abstract
Mechanical ventilation (MV) of mice is widely used in experimental studies. However, conditions for ventilation of mice producing stable lung mechanics, blood pressure and heart rate over several hours are not well defined. In the present study, for the first time, MV with and without recruitment manoeuvres (RM) was compared in healthy mice. The effects of RM on a variety of physiological parameters and pulmonary inflammation were studied over 6h.
C57BL/6 mice were ventilated for 6h at low-VT=8mL/kg, f=180min-1 or high-VT=16mL/kg, f=90min-1 and 3% inspiratory CO2. FiO2 was 0.5 and PEEP 2cmH2O. RM were performed with 30cmH2O for 1s every 5min, 60min or not at all. Lung mechanics were followed by the forced oscillation technique. Blood pressure (BP), ECG, heart frequency (HF), oxygen saturation and body temperature were monitored. Blood gases, histopathology, neutrophil recruitment, microvascular permeability and pro-inflammatory cytokines were examined.
MV with recurrent RM resulted in stable respiratory mechanics. Ventilation without RM worsened lung functions due to alveolar collapse, leading to impaired gas exchange. HF and BP were not affected. Microvascular permeability was highest in atelectatic lungs, whereas neutrophil recruitment and structural changes were strongest in lungs ventilated with high VT. Although IL-6 and KC were markedly elevated in all ventilated mice, levels were clearly reduced by recurrent RM. In contrast, TNF-α and IP-10 remained at baseline, indicating that only moderate lung injury was induced.
We conclude that recurrent RM are required to prevent atelectasis and resulting lung injury during mechanical ventilation of healthy mice.
- © 2011 ERS