The purpose of this clinical trial is to investigate the effects of laparoscopic surgery in the Trendelenburg and Reverse Trendelenburg positions, and variable tidal volume ventilation (V-VCV), pressure-regulated volume-controlled ventilation (PRVC), conventional volume-controlled ventilation (C-VCV), and pressure-controlled ventilation (PCV) on esophageal pressure, airway pressure, tidal volume, intracranial pressure, and cerebral blood flow.
The study aims to address the following primary questions:Does laparoscopic surgery in the Trendelenburg or Reverse Trendelenburg position increase esophageal pressure, airway pressure, and intracranial pressure, and decrease tidal volume and cerebral blood flow? Do variable tidal volume ventilation (V-VCV), pressure-regulated volume-controlled ventilation (PRVC), conventional volume-controlled ventilation (C-VCV), or pressure-controlled ventilation (PCV) increase esophageal pressure, airway pressure, and intracranial pressure, and decrease tidal volume and cerebral blood flow? The investigators will compare variable tidal volume ventilation (V-VCV), pressure-regulated volume-controlled ventilation (PRVC), conventional volume-controlled ventilation (C-VCV), and pressure-controlled ventilation (PCV) to determine which ventilation mode results in the least physiological disturbance for patients.
Participant Procedures:
Participants will: Be positioned according to the surgical requirements.Be randomly assigned to mechanical ventilation with either variable tidal volume ventilation (V-VCV), pressure-regulated volume-controlled ventilation (PRVC), conventional volume-controlled ventilation (C-VCV), or pressure-controlled ventilation (PCV).
Undergo assessments at the following time points: immediately after endotracheal intubation, immediately after pneumoperitoneum, immediately after position change (Trendelenburg or Reverse Trendelenburg), 30 minutes after position change, and 1 hour after position change.
Have their esophageal pressure, airway pressure, intracranial pressure, tidal volume, and internal jugular vein blood flow recorded at each assessment time point.
Age: Unrestricted
American Society of Anesthesiologists (ASA) Physical Status: Class I-III
Surgical Position: Requires the use of either the Trendelenburg position or the Reverse Trendelenburg position during the procedure.
Ventilation: Planned mechanical ventilation is required during the procedure, with suitability for one of the following modes: pressure-regulated volume-controlled ventilation (PRVC), conventional volume-controlled ventilation (C-VCV), or pressure-controlled ventilation (PCV).
Intracranial Disease
Severe Coagulopathy or Current Anticoagulant Therapy
Presence of Psychiatric Illness, Cognitive Impairment, or other condition that precludes the ability to understand or comply with the study.
Parallel
Variable tidal volume ventilation (V-VCV)
Other interventionVariable tidal volume ventilation (V-VCV) ：The initial tidal volume is set at 6-8 ml/kg IBW according to the Ideal Body Weight (IBW), and the maximum tidal volume (Vt\_max) and minimum tidal volume (Vt\_min) are set at 10-20% of the base tidal volume (Vt\_base). Respiratory Rate 12. Inspiratory Flow Rate (IFR) 60L/min, Inspiration to Expiration Ratio (IER) 1:2, Positive End-Expiratory Pressure (PEEP) 5 cm water column, and Inhaled Oxygen Concentration (FiO2) 41%.
Pressure-regulated volume-controlled ventilation (PRVC)
Other interventionPressure-regulated volume-controlled ventilation (PRVC) ：Initial tidal volume is set at 6-8 ml/kg IBW based on Ideal Body Weight (IBW), peak inspiratory pressure is capped at 30 cmH2O, maximum tidal volume (Vt\_max), and minimum tidal volume (Vt\_min) is set at 10-20% of basal tidal volume (Vt\_base). Respiratory Rate (RR) 12, Inspiratory Breathing Ratio (IBR) 1:2, Positive End-Expiratory Pressure (PEEP) 5 cm water column, and Inhaled Oxygen Concentration (FiO2) 98%.
Conventional volume-controlled ventilation (C-VCV)
Other interventionConventional volume-controlled ventilation (C-VCV) ：The initial tidal volume is set at 6-8 ml/kg IBW based on Ideal Body Weight (IBW), and the maximum tidal volume (Vt\_max) and minimum tidal volume (Vt\_min) are set at 10-20% of the basal tidal volume (Vt\_base). Respiratory Rate 12. Inspiratory Flow Rate (IFR) 60L/min, Inspiration to Expiration Ratio (IER) 1:2, Positive End-Expiratory Pressure (PEEP) 5cm water column, FiO2 98%.
Pressure-controlled ventilation (PCV)
Other interventionPressure-controlled ventilation (PCV)：Set inspiratory pressure level, usually 20 cmH2O initial value, Respiratory Rate 12, Inspiratory to Expiratory Ratio 1:2, Positive End-Expiratory Pressure (PEEP) 5 cm water column, Inhaled Oxygen Concentration (FiO2) 98%.
Trendelenburg position
Other interventionTrendelenburg position：Lower the head of the bed by 30 degrees with no more than 15 degrees of lateral tilt.
Reverse Trendelenburg position
Other interventionReverse Trendelenburg position：Elevate the head of the bed by 30 degrees with no more than 15 degrees of lateral tilt.
8
Treatment groupsSee each treatment group below.
esophageal pressure
airway pressure
intracranial pressure
tidal volume
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