Major Differences in the Pathological Course of Smoke and Burn Injury among Different Modes of Ventilation

Abstract

The physiological consequences of different modes of ventilation for animals with acute respiratory distress syndrome (ARDS) are well characterized. There is much less information available on the microscopic and molecular pathology. We hypothesized that differences in pathology of acute ARDS would be present after different modes of ventilation, and that those differences could be used to further refine ventilatory strategies. Female Merino sheep (30–40 kg) were subjected to 48 breaths of cotton smoke and a 40% body surface area full-thickness burn. The animals were then randomly treated with either low tidal volume ventilation (LTV), arteriovenous removal of CO2 (AVCO2R), or high frequency percussive ventilation (HFPV) after reaching a PaO2/FiO2 value of 200 and subsequently sacrificed at 72 h post-injury. Laser scanning microscopy was performed with a Zeiss LSM UV META confocal microscope. Myeloperoxidase in lung tissue was measured by a spectrophotometric method using diaminobenzidine as a substrate. Il-8 was determined with a sandwich ELISA. Type II alveolar epithelial cells were identified with anti-thyroid transcription factor-1, and type I alveolar epithelial cells were identified with anti-aquaporin-5 or Lysopericum esculentum lectin.