Shoulder pain is common after laparoscopic surgeries. multiple maneuvers are in use to decrease its incidence with variable results. This study aims to investigate the effect of mild hyperventilation to an End-tidal CO2 level of 30-32 mmHg on the occurrence of postoperative shoulder pain. This is carried out through a comparison of the incidence of postoperative shoulder pain an intervention group to that in a control one with a normal End Tidal CO2 35-40 mmHg). controlling for all other variables.

This novel technique is based on the theory that shoulder pain is caused by diaphragmatic irritation by CO2 during laparoscopic surgery. The investigators postulate that lowering the CO2 level in the plasma, will lower tissue CO2 level in the diaphragm and decrease the hypothesized irritation. In this study, patients will be divided into an interventional group which will receive mild intraoperative hyperventilation determined by an End-Tidal CO2 level of 30-32 mm Hg and a control group in which End Tidal CO2 is kept at normal levels (35-40 mmHg). All other intraoperative factors will be standardized for all patients. Patients will be followed up postoperatively and asked whether the participants developed shoulder pain as a primary study outcome. The pain will be recorded in terms of severity, site, and position, and any associations (Nausea and vomiting). Appropriate statistical tests will be used to check for any significant effects of the technique.

Inclusion Criteria:

• 18 years old
• No mental illnesses
• American Society of Anesthesiologists (ASA) class I&II,
• Patients undergoing laparoscopic sleeve gastrectomy.
• No previous intrabdominal surgeries.

Exclusion Criteria:

• ASA class >II,
• previous abdominal surgeries.
• mental illnesses.

Only the anesthetist administering the anesthesia and mechanical ventilation is Awarem of the arm.