Inspiratory Contribution of Pressure Support-ventilated Patients in Different PMI Conditions

Baseline ventilators were set by the principle of keeping VT/PBW at 6-8ml/kg and RR at 20-30 breaths/min and the decision of the responsible ICU physician. After then the fraction of inspired oxygen (FiO2), positive expiratory end pressure (PEEP), trigger sensitivity, and cycle-off criteria remain unchanged. Upward and downward PS level adjustments were performed from the baseline PS level at a 1cm H2O interval. Every PS level was maintained for 20 minutes and then three end-inspiratory holdings (2-3seconds) and three end-expiratory holdings were performed. PMI mean value was measured and calculated at every PS level. To avoid additional injury to the lung and diaphragm, the airway peak pressure (Ppeak) was limited to 30cmH2O, and titrating PS was stopped until PMI was less than -1cmH2O and more than 3cmH2O.The inspiratory effort is measured as the pressure generated by inspiratory muscles using esophageal pressure monitoring.