Titration of PS Guided by FI : A Pilot Study

The goal of this single-center, pilot, randomized controlled trial is to evaluate the feasibility and preliminary efficacy of using the Flow Index (FI) to guide Pressure Support (PS) titration in adult patients receiving Pressure Support Ventilation (PSV) who are expected to require invasive mechanical ventilation for more than 48 hours.

The main questions it aims to answer are:

* Is FI-guided PS titration feasible and safe in a clinical ICU setting, as assessed by the proportion of failed safety assessments and the emergency termination rate? * Does FI-guided PS titration result in a greater proportion of data collection points with respiratory muscle pressure (Pmus) within the normal range (5-10 cmH₂O) compared to conventional PS titration based on tidal volume and respiratory rate? Researchers will compare the FI-guided PS titration group to the conventional PS titration group to see if FI-guided adjustment improves the proportion of assessments with adequate inspiratory effort (avoiding both excessive and insufficient support), and whether it leads to differences in clinical outcomes including duration of mechanical ventilation, extubation failure rate, tracheostomy rate, length of ICU and hospital stay, and in-hospital all-cause mortality.

Participants will:

* Be randomly assigned in a 1:1 ratio to receive either conventional PS titration (adjusting PS to achieve tidal volume of 6-8 mL/kg predicted body weight and respiratory rate of 20-30 breaths/min) or FI-guided PS titration (adjusting PS to maintain FI between 2.6 and 4.5) * Complete an intervention period with PS adjustments performed twice daily (at 8:00 AM and 8:00 PM) according to the assigned protocol * Have Pmus assessed at each data collection point to determine whether inspiratory effort falls within the target range * Undergo a 2-minute safety assessment after each PS adjustment to ensure adequate ventilation and avoid excessive airway pressures or respiratory distress * Be followed for up to 28 days after enrollment or until ICU discharge, with extended follow-up to hospital discharge or death for clinical outcome evaluation