Effect of Ventilation Mode in the Pupillary Light Reflex: A Crossover Study
Trial statusNot yet recruiting
Trial phaseNot applicable
Trial typeInterventional
Biological sexAll
Age18+
SponsorEvangelismos Hospital
About this trial
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.
Eligibility criteria
This trial does not accept healthy volunteersQualifiers
Adult patients (≥18 years old)
Receiving positive-pressure mechanical ventilation
Under light or no sedation (e.g., RASS score between -2 and 0)
Clinically assessed by the treating physician as not yet ready for weaning from mechanical ventilation
Disqualifiers
Acute or chronic neurological disease affecting brainstem function or pupillary responses
Dyssynchrony with the ventilator or need for high ventilatory support adjustments
Facial injuries, edema, or conditions precluding accurate pupillometry
Use of neuromuscular blocking agents within the prior 6 hours
Trial design
Design model
Crossover
Treatments tested in this trial
Volume Control Ventilation
Other interventionStandard mode of mechanical ventilation delivering a preset tidal volume. Commonly used in ICU patients requiring controlled ventilation.
Pressure Control Ventilation
Other interventionPressure-targeted ventilation mode that delivers breaths at a fixed pressure. Commonly used in critically ill patients.
Pressure-Regulated Volume Control (PRVC)
Other interventionHybrid ventilation mode that automatically adjusts inspiratory pressure to achieve a preset tidal volume.
Treatment groups
36 Participants
are divided into 6 treatment groups6
Treatment groupsSee each treatment group below.
Group A: Sequence A: VC → PC → PRVCExperimental treatment 3 interventions
Group B: Sequence B: VC → PRVC → PCOther 3 interventions
Group C: Sequence C: PC → VC → PRVCOther 3 interventions
Group D: Sequence D: PC → PRVC → VCOther 3 interventions
Group E: Sequence E: PRVC → VC → PCOther 3 interventions
Group F: Sequence F: PRVC → PC → VCOther 3 interventions
Trial outcomes
Primary outcomes
1
Maximum Pupillary Constriction Velocity
Change in maximum pupillary constriction velocity (mm/s) in response to standardized light stimulus, as measured by the NPi-200 pupillometer, under three modes of mechanical ventilation: Volume Control (VC), Pressure Control (PC), and Pressure-Regulated Volume Control (PRVC).
Time frame
At 30 minutes after each ventilation mode initiation (VC, PC, PRVC).Secondary outcomes
1
Neurological Pupil Index (NPi)
Change in NPi value recorded under each ventilation mode, reflecting pupillary reactivity and brainstem function.
Time frame
At 30 minutes after each ventilation mode initiation (VC, PC, PRVC).2
Constriction Latency
Change in latency to onset of pupil constriction (seconds), measured using the NPi-200.
Time frame
At 30 minutes after each ventilation mode initiation (VC, PC, PRVC).3
Dilation Velocity
Change in maximum dilation velocity (mm/s) following light stimulus, measured with the NPi-200.
Time frame
At 30 minutes after each ventilation mode initiation (VC, PC, PRVC).4
Maximum Pupil Diameter
Change in maximum pupil diameter (mm) measured before light stimulation under each ventilation mode.
Time frame
At 30 minutes after each ventilation mode initiation (VC, PC, PRVC).Other outcomes
1
Exploratory Outcome Measure - Heart Rate Variability (HRV)
HRV derived from ECG to explore autonomic nervous system modulation across ventilation modes (optional, if data acquisition becomes feasible).
Time frame
Time interval between 15-30 minutes after the initiation of each ventilation mode (VC, PC, PRVC)2
Systolic Blood Pressure (mmHg)
Systolic blood pressure will be recorded during each ventilation mode to assess cardiovascular stability.
Time frame
At 30 minutes after each ventilation mode initiation (VC, PC, PRVC).3
Diastolic Blood Pressure (mmHg)
Diastolic blood pressure will be recorded during each ventilation mode to assess cardiovascular stability.
Time frame
At 30 minutes after each ventilation mode initiation (VC, PC, PRVC).4
Mean Arterial Pressure (mmHg)
Mean arterial pressure (MAP) will be recorded to evaluate overall hemodynamic stability.
Time frame
At 30 minutes after each ventilation mode initiation (VC, PC, PRVC).Sponsors and contacts
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Source ClinicalTrials.gov
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