During general anesthesia, particularly in patients undergoing spine surgery in the prone (face-down) position, increased intrathoracic and abdominal pressure may reduce lung compliance and promote the development of atelectasis (partial lung collapse). Atelectasis can impair intraoperative oxygenation and may increase the risk of postoperative pulmonary complications. Alveolar recruitment maneuvers (ARM) are routinely used in anesthesia practice to reopen collapsed lung regions; however, it remains unclear whether periodic application of ARM throughout surgery provides additional benefit compared with standard single-time application.
This prospective, randomized controlled clinical study aims to evaluate whether periodic alveolar recruitment maneuvers applied during elective spine surgery in the prone position reduce intraoperative atelectasis and improve respiratory mechanics compared with the standard approach of performing ARM only after positioning and before extubation. Adult patients undergoing elective spine surgery under general anesthesia will be randomly assigned to either a periodic ARM group or a standard ARM group.
Lung aeration will be assessed using lung ultrasound, a non-invasive and radiation-free bedside imaging method. The primary outcome is the incidence of intraoperative atelectasis assessed before extubation. Secondary outcomes include lung ultrasound aeration scores, respiratory mechanics parameters (such as airway pressures and compliance), oxygenation indices, and the occurrence of transient intraoperative respiratory or hemodynamic events.
The findings of this study may help optimize intraoperative ventilation strategies in prone spine surgery and contribute to improved perioperative respiratory safety.
Adults aged 18 to 65 years
Scheduled for elective lumbar spine surgery under general anesthesia
Surgery planned to be performed in the prone position
Expected surgical duration of at least 2 hours
Body mass index (BMI) greater than 30 kg/m²
History of thoracic surgery
Known or suspected chronic pulmonary disease (e.g., chronic obstructive pulmonary disease, restrictive lung disease)
Clinically significant cardiac disease
Parallel
Alveolar Recruitment Maneuver
Procedure/SurgeryAlveolar recruitment maneuvers will be performed under general anesthesia using standard mechanical ventilation techniques within routine clinical safety limits. After prone positioning, a baseline recruitment maneuver will be applied by stepwise increasing positive end-expiratory pressure (PEEP) from 8 cmH₂O to 10 cmH₂O and 15 cmH₂O while maintaining an upper airway pressure limit of ≤30 cmH₂O for approximately 10 seconds. Following the maneuver, mechanical ventilation will continue with a PEEP level of approximately 8 cmH₂O according to routine clinical practice. In the periodic recruitment group, additional recruitment maneuvers will be repeated approximately once per hour during the intraoperative period. In the standard recruitment group, no additional intraoperative maneuvers will be applied apart from a final recruitment maneuver performed before extubation as part of routine anesthetic care.
Incidence of Significant Intraoperative Atelectasis Assessed by Lung Ultrasound
Significant intraoperative atelectasis will be defined as the presence of significant loss of lung aeration identified by transthoracic lung ultrasound, corresponding to a regional score of 2 or higher in at least one predefined lung region using a standardized 12-region semi-quantitative lung ultrasound aeration scoring system. In this system, each region is scored from 0 to 3, with higher scores indicating greater loss of lung aeration. Lung ultrasound examinations will be performed according to a predefined scanning protocol, and image interpretation will be conducted by an assessor blinded to group allocation.
Peak Inspiratory Pressure
Peak inspiratory pressure will be recorded from the anesthesia ventilator during mechanical ventilation and documented prospectively to characterize intraoperative respiratory mechanics.
Dynamic Lung Compliance
Dynamic lung compliance will be calculated from ventilator-derived tidal volume and airway pressure measurements during mechanical ventilation and documented prospectively to characterize respiratory system mechanics under general anesthesia.
Peripheral Oxygen Saturation
Peripheral oxygen saturation (SpO2) will be recorded using standard pulse oximetry at predefined intraoperative study time points for analysis. Peripheral oxygen saturation (SpO₂) will be continuously monitored using standard pulse oximetry during general anesthesia and early postoperative recovery. Recorded values will be documented at predefined time points for analysis.
Incidence of Oxygen Desaturation
Oxygen desaturation will be defined as any documented episode of peripheral oxygen saturation (SpO2) below 95 percent measured by pulse oximetry during intraoperative monitoring or within 30 minutes after arrival in the post-anesthesia care unit (PACU).
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