Effect of Ventilation Mode in the Pupillary Light Reflex: A Crossover Study

The goal of this clinical trial is to explore whether different modes of mechanical ventilation affect pupillary constriction velocities in critically ill patients without brain injury. The study aims to determine whether the type of mechanical ventilation (volume control, pressure control, or pressure-regulated volume control) influences the maximum and mean constriction velocity measured by automated pupillometry. The trial also investigates whether changes in pupil dynamics reflect subtle alterations in brainstem-autonomic interaction induced by ventilation mode. The comparison involves volume control, pressure control, and pressure-regulated volume control in a randomized crossover design to assess whether ventilation mode has a measurable effect on pupil response. Eligible participants will be intubated ICU patients receiving assist control ventilation who are not yet ready for spontaneous breathing trials. Serial pupillometry measurements will be conducted while participants are ventilated with each mode for at least 15 minutes. Sedation and lighting conditions will remain consistent throughout the protocol. Participants with acute or chronic neurologic conditions or ventilator dyssynchrony will be excluded.