Mechanical ventilation of healthy rats suppresses peripheral immune function

Area of Science:

• Immunology
• Respiratory Medicine
• Critical Care

Background:

• Mechanical ventilation is crucial for acute respiratory distress syndrome (ARDS) patients.
• High airway pressures during ventilation may cause lung injury and affect systemic immune responses.
• Understanding these effects is vital for optimizing ventilator strategies and patient outcomes.

Purpose of the Study:

• To investigate the impact of injurious mechanical ventilation strategies on peripheral immune function in healthy rats.
• To compare the effects of low vs. high peak inspiratory pressure (PIP) and positive end-expiratory pressure (PEEP) on immune parameters.
• To determine if ventilator-induced lung inflammation correlates with peripheral immune suppression.

Main Methods:

• Rats were subjected to three ventilation strategies: low PIP/PEEP, high PIP/PEEP, and high PIP/zero PEEP (ZEEP).
• A non-ventilated, anesthetized sham-operated group served as a reference.
• Immune function was assessed by measuring macrophage inflammatory protein (MIP)-2, splenic natural killer (NK) cell activity, splenocyte proliferation, and cytokine production (IL-10, interferon-gamma).

Main Results:

• High PIP ventilation, regardless of PEEP, increased MIP-2 levels in the lung and plasma.
• Compared to low PIP/PEEP, high PIP/PEEP ventilation reduced NK cell activity, splenocyte proliferation, MIP-2, and IL-10 production.
• High PIP/ZEEP ventilation caused more pronounced decreases in immune function and also lowered interferon-gamma levels.

Conclusions:

• High positive inspiratory pressure ventilation induces lung inflammation and peripheral immune suppression.
• Ventilator-induced peripheral immune suppression may be a contributing factor to poor outcomes in ARDS.
• Optimizing ventilator settings to minimize lung injury is crucial for preserving immune function.