General anesthesia and mechanical ventilation promotes atelectasis and airway closure. The open-lung approach (OLA) strategy restores the functional residual capacity. Pulse oximetry hemoglobin saturation (SpO2) using room air can diagnose shunt induced by lung collapse during general anesthesia and the SpO2 breathing air was useful to detect the lung´s opening and closing pressure during a recruitment maneuver (RM) in morbidly obese anesthetized patients.

Investigators hypothesized that the SpO2 breathing air can personalize the open-lung approach.

Increase in airway pressure until the SpO2 reaches 97% (lung´s opening pressure) during the incremental positive end-expiratory (PEEP) limb. Decrease in the PEEP level until the SpO2 decreases bellow 97% (lung´s closing pressure)

Inclusion Criteria:

• Non-obese patients with ASA physical status I-III undergoing elective abdominal laparoscopic surgery with an expected operating time of less than 2 hours were included.

Exclusion Criteria:

• age of <18 years,
• preoperative SpO2 ≤97% while breathing room air, and
• patients with previous known cardiac or respiratory disease.

The study included all patients with ASA status I-III scheduled for elective abdominal laparoscopic surgery.

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