Title: Individualized lung recruitment maneuver guide by pulse-oximetry in anesthetized non-obese patients undergoing laparoscopy. 
Authors: Abigail Villena, Ana Jurado, Juan Carrizo, Alejandro Duca, Marina Soro, Carlos Ferrando.
Background and Goal of Study: General anesthesia and mechanical ventilation promote atelectasis which negatively affects the lung function1 and may promote postoperative pulmonary complications. The open-lung approach (OLA) is aimed at restoring the functional lung volume2. In a recent study pulse oximetry hemoglobin saturation (SpO2) under low FIO2 was useful to monitor the lung´s opening and closing pressure in morbidly obese anesthetized patients3. Our goal was to test whether SpO2 can personalize the implementation of an open-lung approach during laparoscopy. 
Methods: Thirty patients with SpO2 ≥97% on room-air before anesthesia were studied. After anesthesia induction and capnoperitoneum the FIO2 was reduced to 0.21. Those patients whose SpO2 decreased below 97% complete the following phases: 1) First recruitment maneuver (RM), until reaching lung´s opening pressure, defined as the inspiratory pressure level yielding a SpO2 ≥97%; 2) a positive end-expiratory (PEEP) titration trial until reaching lung´s closing pressure defined as the PEEP level yielding a SpO2 <97%; 3) a second RM was performed and, 4) ongoing ventilation with PEEP adjusted above the detected closing pressure. 
Results: Breathing air, 24 of 30 patients (80%) showed SpO2 <97% together PaO2/FIO2 ˂400mmHg. The mean opening pressures were found at 40(6) and 33(4) cmH2O during the first and second RM, respectively. The closing pressure was 11(5) cmH2O. This SpO2-guide approach reached an open-lung condition (table 1). SpO2 discriminates the lung’s opening and closing pressures with accuracy taking the reference PaO2/FIO2 (area under the receiver-operating-curve of 0.88, 95%CI: 0.80 – 0.97). 
Conclusion: The non-invasive SpO2 value can easily individualize an open-lung approach.
References
1.	Hedenstierna G, et al. Airway closure and distribution of inspired gas in extremely obese, breathing spontaneously and during anesthesia with intermittent positive pressure ventilation. Acta Anesthesiol Scand 1976; 20:334-42. 
2.	Futier E, et al. Intraoperative recruitment maneuver reverses detrimental pneumoperitoneum-induced respiratory effects in healthy weight and obese patients undergoing laparoscopy. Anesthesiology 2010; 113:1310-9.
3.	Tusman G, et al. Noninvasive monitoring of lung recruitment maneuvers in morbidly obese patients: the role of pulse oximetry and volumetric capnography. Anesth Analg 2014; 118:137-44.