Protective Ventilation vs. Hypercapnia for the Attenuation of Ventilator-Associated Lung Injury

Abstract

Mechanically ventilated patients are at risk of developing Ventilator-Associated Lung Injury (VALI). Improved ventilation strategies by lung-protective settings may cause hypercapnia. This study investigated whether attenuation of VALI is attributed to protective ventilation with low tidal volume (VT) or hypercapnia. Lung injury was induced in rats by instillation of 1.25M HCl. Ten rats each were ventilated for 4 hours with: Conventional Normocapnia (highVT), Lung-Protective Ventilation (VT¬ 8mL/Kg), Injurious Normocapnia (highVT, added dead space), Conventional Hypercapnia (highVT, inhaled CO2), Protective Hypercapnia (VT 8mL/Kg, inhaled CO2) and Permissive Hypercapnia (VT 8mL/Kg, hypoventilation). Lung-Protective Ventilation reduced pulmonary edema compared to Conventional and Injurious Normocapnia. Therapeutic hypercapnia reduced alveolar damage and inflammation by reducing IL-6 and MCP-1 in the lung, and IL-1? and TNF-? systemically. Therapeutic hypercapnia may be more effective in attenuating some of the biomarkers of VALI and protecting the lung than protective ventilation alone.