This randomized controlled trial compares volume-controlled ventilation (VCV) and pressure-controlled ventilation (PCV) in adult patients undergoing elective laparoscopic cholecystectomy under general anesthesia. The study evaluates the effects of both ventilation modes on static lung compliance and end-tidal carbon dioxide (EtCO₂) at predefined intraoperative time points. The objective is to determine whether pressure-controlled ventilation provides improved respiratory mechanics and more effective ventilation compared with volume-controlled ventilation during laparoscopic surgery.

Laparoscopic cholecystectomy is one of the most commonly performed surgical procedures under general anesthesia. Creation of carbon dioxide pneumoperitoneum during laparoscopic surgery increases intra-abdominal pressure, resulting in reduced functional residual capacity, decreased lung compliance, increased airway pressures, and alterations in carbon dioxide elimination. These physiological changes may impair respiratory mechanics and increase the risk of perioperative pulmonary complications. Therefore, selection of an appropriate mechanical ventilation strategy is essential to maintain adequate ventilation and optimize respiratory function during laparoscopic surgery. The objective of this randomized controlled trial is to compare the effects of volume-controlled ventilation and pressure-controlled ventilation on static lung compliance and end-tidal carbon dioxide (EtCO₂) in adult patients undergoing elective laparoscopic cholecystectomy under general anesthesia. The study aims to determine whether pressure-controlled ventilation provides superior intraoperative respiratory mechanics compared with volume-controlled ventilation while maintaining adequate ventilation throughout the surgical procedure.

This is a prospective, single-center, randomized controlled trial conducted in the Department of Anaesthesia, Nishtar Hospital, Multan. A total of 60 adult patients aged 25-50 years, of either sex, classified as American Society of Anesthesiologists (ASA) physical status I or II and scheduled for elective laparoscopic cholecystectomy, will be enrolled after obtaining written informed consent. Patients with uncontrolled cardiopulmonary disease, diabetes mellitus, significant renal or hepatic impairment, chronic systemic illness, body mass index below 18.5 kg/m² or above 24.9 kg/m², or recent respiratory tract infection within the preceding three weeks will be excluded.

Participants will be allocated in a 1:1 ratio using computer-generated randomization by an independent third party into one of two study groups. Group A will receive volume-controlled ventilation, while Group B will receive pressure-controlled ventilation. Allocation concealment will be maintained until initiation of mechanical ventilation. Baseline demographic variables including age, sex, and body mass index will be recorded before induction of anesthesia.

A standardized anesthetic technique will be used for all participants. Mechanical ventilation settings will include a tidal volume of 8 mL/kg (with inspiratory pressure adjusted in the PCV group to achieve the target tidal volume), respiratory rate initially set at 12 breaths per minute and subsequently adjusted to maintain an end-tidal carbon dioxide concentration between 32 and 38 mmHg, inspiratory-to-expiratory ratio of 1:2, fraction of inspired oxygen (FiO₂) of 0.40, positive end-expiratory pressure (PEEP) of 5 cmH₂O, and oxygen saturation maintained above 95%. Carbon dioxide pneumoperitoneum will be maintained with an intra-abdominal pressure of 12-15 mmHg throughout the procedure.

Static lung compliance and end-tidal carbon dioxide will be recorded at three predefined intraoperative time points: five minutes after induction of anesthesia, fifteen minutes after carbon dioxide insufflation in the reverse Trendelenburg position, and ten minutes after carbon dioxide desufflation. Measurements will be recorded using the integrated monitoring systems of the anesthesia workstation by a trained anesthesiologist who is not involved in group allocation. Blinding of the anesthesia provider is not feasible because of the nature of the interventions; however, the primary outcome measures are objective monitor-derived variables, minimizing the risk of measurement bias.

The primary outcome measures are static lung compliance and end-tidal carbon dioxide measured at the predefined intraoperative time points. Data will be analyzed using SPSS version 26. Continuous variables will be summarized as mean ± standard deviation or median with interquartile range according to data distribution, while categorical variables will be expressed as frequencies and percentages. Between-group comparisons will be performed using the independent t-test or Mann-Whitney U test as appropriate, with stratification for age, sex, and body mass index where indicated.

This study is expected to provide evidence regarding the optimal ventilation strategy during laparoscopic cholecystectomy and may contribute to improved intraoperative respiratory management and enhanced patient safety in routine anesthetic practice.

Inclusion Criteria:

• Adult patients aged 25-50 years.
• Either sex.
• ASA physical status I or II.
• Scheduled for elective laparoscopic cholecystectomy under general anaesthesia.
• Written informed consent obtained.

Exclusion Criteria:

• ASA physical status III or IV.
• Body mass index (BMI) greater than 35 kg/m².
• Significant pulmonary disease (e.g., COPD, asthma, restrictive lung disease).
• Significant cardiovascular disease.
• Pregnancy.
• Previous upper abdominal surgery.
• Conversion to open cholecystectomy.
• Refusal to participate.

Individual participant data will not be shared because no formal data-sharing plan has been established. Participant confidentiality and institutional ethical requirements will be maintained.

Participants are unaware of the assigned ventilation mode. Outcome measurements are objective monitor-derived parameters recorded using the anesthesia workstation, minimizing measurement bias. Care providers are not blinded because of the nature of the intervention.