Effect of Intraoperative Salbutamol Administration on Mechanical Power and Respiratory Mechanics in Obese Patients Undergoing Laparoscopic Bariatric Surgery

Mechanical power will be measured directly by the ventilator/respiratory monitoring device using ventilator parameters (tidal volume, respiratory rate, peak and plateau pressures, driving pressure, and compliance) at T0, T1, and T2. The primary outcome is the difference in mechanical power between the Salbutamol and placebo groups over time.

Peak airway pressure will be measured directly by the ventilator/respiratory monitoring device at T0, T1, and T2 to assess intraoperative respiratory mechanics.

Plateau pressure will be measured by the ventilator device at T0, T1, and T2 to evaluate changes in lung mechanics.

Driving pressure (Pplat minus PEEP) will be measured via the ventilator device at all intraoperative time points to assess lung stress.

Airway resistance will be recorded from the ventilator/monitoring device at each time point to evaluate intraoperative airway changes.

Lung compliance will be measured by the ventilator at T0, T1, and T2 to assess changes in respiratory mechanics.

Lung elastance will be measured directly by the ventilator/monitoring device at each intraoperative time point (T0, T1, T2) to evaluate the stiffness of the respiratory system and its changes due to pneumoperitoneum and Ventolin/SF administration.

Heart rate will be monitored continuously and recorded at T0, T1, and T2 to evaluate intraoperative hemodynamic stability and potential effects of pneumoperitoneum and Ventolin/SF administration.

Mean arterial pressure will be monitored continuously and recorded at T0, T1, and T2 to assess intraoperative hemodynamic stability and the effects of pneumoperitoneum and Ventolin/SF administration.

Incidence of postoperative pulmonary complications will be assessed using the Melbourne Group Scale (MGS). A score greater than 4 indicates the presence of a postoperative pulmonary complication. Criteria include:

Temperature >38°C

White cell count >11.2 ×10⁹/L or use of respiratory antibiotics

Physician diagnosis of pneumonia or chest infection

Chest X-ray findings of atelectasis or consolidation

Production of purulent (yellow/green) sputum different from preoperative sputum

Positive microbiological analysis of sputum

SpO₂ <90% in ambient air

Re-admission to or prolonged stay (>36 h) in ICU/high dependency unit for respiratory problems

Patients meeting ≥4 of these criteria at any assessment point will be recorded as having a postoperative pulmonary complication.