Individualized vs Standard PEEP and Oxygen Reserve Index in Laparoscopic Hernia Surgery

General anesthesia combined with pneumoperitoneum and Trendelenburg positioning significantly alters respiratory mechanics. These changes can reduce functional residual capacity (FRC), promote atelectasis, and impair gas exchange - particularly in laparoscopic surgery.

Individualized PEEP, determined through a recruitment maneuver followed by PEEP titration, has been shown to reduce driving pressure and improve dynamic lung compliance compared to fixed PEEP strategies.

The Oxygen Reserve Index (ORI) is a novel non-invasive monitoring parameter that continuously tracks partial oxygen pressure changes in the 100-200 mmHg range, providing early warning of desaturation before SpO2 drops.

In this prospective observational study, 60 adult patients (ASA I-III, aged 18-75) scheduled for elective laparoscopic unilateral inguinal hernia repair under general anesthesia will be enrolled. Patients will receive either standard PEEP (5 cmH₂O) or individualized PEEP based on the attending anesthesiologist's routine clinical preference.

Hemodynamic and respiratory parameters including ORI, SpO2, airway pressures, tidal volume, dynamic compliance, and BIS will be recorded at six time points: before anesthesia (T0), 5 minutes post-intubation (T1), 10 minutes post-Trendelenburg (T2), 20 minutes post-Trendelenburg (T3), after desufflation (T4), and at postoperative 20 minutes (T5).

Lung ultrasound scoring (0-3 per zone, 12-zone protocol) will be performed preoperatively and postoperatively to assess atelectasis. Arterial blood gas analysis will provide additional oxygenation data.

The primary outcome is the effect of individualized versus standard PEEP on perioperative oxygenation as measured by ORI. The secondary outcome is the comparison of atelectasis prevention efficacy between the two PEEP strategies assessed by lung ultrasound score.

Inclusion criteria

• Aged 18-75 years
• ASA physical status I-III
• Scheduled for elective laparoscopic unilateral inguinal hernia repair under general anesthesia
• Body mass index (BMI) < 35 kg/m²
• Written informed consent obtained

Exclusion criteria

• Age below 18 or above 75 years
• ASA physical status IV-V
• Emergency surgical procedure
• Severe chronic or restrictive pulmonary disease
• Pulmonary hypertension
• Obstructive sleep apnea syndrome
• Preoperative peripheral oxygen saturation < 94% on room air
• Respiratory tract infection within the last two weeks
• Severe cardiac failure (NYHA III-IV)
• Pregnancy
• Communication difficulties preventing NRS assessment
• Surgical complications during the procedure
• Operation duration exceeding 3 hours
• Refusal to provide informed consent