Surgical site infections (SSI) are the most common healthcare-associated infections and sources of morbidity and over-mortality. Factors that have been proven to reduce SSI include antimicrobial prophylaxis, maintenance of perioperative normothermia, avoidance of hyperglycemia, proper surgical techniques, and adequate pain relief postoperatively

In 2016, a systematic review and meta-analysis assessing the effects of systematic high FiO2 (80%) compared with standard FiO2 (30%) concluded that high FiO2 was associated with a reduction of SSI in patients undergoing surgery under general anesthesia. Consequently, the WHO recommended that "adult patients undergoing general anesthesia should receive an 80% FiO2 intra-operatively to reduce the risk of SSI".These recommendations have sparked a large debate on the benefits and harms of hyperoxemia. From the theoretical point-of-view, several pro (prevention of hypoxemia, SSI, and postoperative nausea and vomiting) and con (respiratory adverse events, increased production of harmful "reactive oxygen species") arguments have been raised by believers and detractors of high FiO2. Accordingly, and despite these recommendations, anesthetists still used a wide range of intraoperative FiO2 in daily practice and frequently changed FiO2 settings during surgery unrelated to patients' PaO2 or SpO2.

The PROXI study, the largest multicenter randomized controlled trial specifically designed to assess the role of high vs. low intraoperative FiO2 on SSI, did not report any reduction of the incidence of SSI with the administration of 80% FiO2 during colorectal surgery. Similarly, the recent multicenter randomized iPROVE-O2 trial that included 740 patients undergoing major abdominal surgery, ventilated intraoperatively with an evidence-based protective strategy, reported a similar SSI rate between the 30% and 80% FiO2 groups.

Inclusion Criteria:

• - BMI of <35 kg/m2
• scheduled for elective abdominal laparotomy/ laparoscopy under general anesthesia with an expected surgical time longer than 2 h.
• ASA I and II

Exclusion Criteria:

• - Patients undergoing minor procedures, where the expected duration of surgery will be less than 1 hour.
• emergency surgeries for bowel obstruction.
• abdominal surgery for vascular or plastic indications.
• patients with a recent history of fever,
• patients with uncontrolled diabetes mellitus,
• patient with known immunological dysfunction (on steroids, decompensated liver disease, HIV, etc.).