Mechanical ventilation induces inflammation, lung injury, and extra-pulmonary organ dysfunction in experimental...

Area of Science:

• Pulmonary Medicine
• Critical Care Medicine
• Infectious Disease

Background:

• Mechanical ventilation (MV) is crucial for respiratory failure but linked to ventilator-associated pneumonia (VAP).
• Staphylococcus aureus is a key pathogen in VAP.
• MV may contribute to acute lung injury (ALI) and acute respiratory distress syndrome (ARDS).

Purpose of the Study:

• To investigate if MV exacerbates ALI and systemic inflammation during Staphylococcus aureus pulmonary infection.
• To determine MV's role in the pathogenesis of ALI and multiple organ dysfunction syndrome (MODS).

Main Methods:

• Induced Staphylococcus aureus pulmonary infection in spontaneously breathing and mechanically ventilated mice.
• Analyzed bronchoalveolar lavage fluid (BALF) for neutrophil influx and inflammatory cytokines.
• Assessed protein permeability across the alveolar-capillary barrier.
• Measured peripheral blood cytokine expression and extrapulmonary organ function (liver, kidney).

Main Results:

• MV combined with bacteria significantly increased neutrophil influx and pro-inflammatory cytokines (KC, MIP-2, TNF-alpha, IL-6) in BALF.
• MV augmented alveolar-capillary permeability to proteins.
• MV induced systemic inflammation, evidenced by increased cytokines in peripheral blood and hepatic/renal dysfunction.
• Bacterial clearance and dissemination were unaffected by MV.

Conclusions:

• Mechanical ventilation exacerbates pulmonary and systemic inflammation during S. aureus infection.
• MV contributes to the pathogenesis of ALI and MODS.
• MV's detrimental effects occur independently of its impact on bacterial clearance or dissemination.