Usefulness of pressure-controlled ventilation at high inspiratory pressures to induce acute lung injury in mice

Acute lung injury (ALI), as occurs with prolonged mechanical ventilation, contributes to morbidity and mortality of critical illness, and studies on novel genetic or pharmacological targets are areas of intense investigation. Here, we systematically tested a murine model of ALI by using pressure-controlled ventilation to induce ventilator-induced lung injury. For this purpose, C57BL/6 or Sv129 mice were anesthetized and underwent tracheotomy followed by induction of ALI via mechanical ventilation. Mice were ventilated in a pressure-controlled setting at different inspiratory pressure levels (15–45 mbar) and over different times (0–90 min, 100% oxygen). As outcome parameters, we assessed pulmonary edema (wet-to-dry ratios), bronchoalveolar fluid albumin content, pulmonary myeloperoxidase activity, macrophage inflammatory protein-2, and pulmonary gas exchange. These studies revealed maximal differences in severity of lung injury between different mouse strains after 90 min of ventilation time at 45 mbar. Use of lower concentrations of inspired oxygen did not alter disease severity. Increases of CD73 transcript (5′-ectonucleotidase, pacemaker of extracellular adenosine production) or total pulmonary adenosine levels with mechanical ventilation were less pronounced in C57BL/6 mice, suggesting attenuated adenosine protection in C57BL/6 mice. Together, these studies demonstrate feasibility of this model to induce murine ALI.