The effect and mechanism of PA colonization on PA VAP-induced lung injury has not been clearly defined. Ranieri et al. previously demonstrated that in patients using controlled mechanical ventilation with a respiratory rate of 10–15/min and a tidal volume targeted to maintain the PaCO2 between 35 and 40 mmHg, a significant increase of IL-1β, IL-6, and IL-1 receptor agonist in BALF was observed at 24 h after ventilation [26]. Here, IL1B is linked to ventilator-associated pneumonia.