ORI-Guided FiO₂ Titration in Prone Spine Surgery: Impact on Postoperative Atelectasis Assessed by Lung Ultrasound

NCT07375173 | Not Yet Recruiting

• 1 other identifier: AEŞH-EK-2025-301
• Study Type: interventional
• Target: 74
• Locations: 0 countries
• Sites: N/A

Brief Summary

Atelectasis is a frequent pulmonary complication after general anesthesia, often triggered by preoxygenation and intraoperative hyperoxia. High inspiratory oxygen fractions (FiO₂) can promote absorption atelectasis, ventilation-perfusion mismatch, hemodynamic alterations, and oxidative injury. This study evaluates the effect of two intraoperative oxygen management strategies-oxygen reserve index (ORI)-guided FiO₂ titration versus fixed 50% FiO₂-on postoperative atelectasis in patients undergoing thoracolumbar spine surgery under general anesthesia. Atelectasis severity will be assessed using lung ultrasonography (LUS), scored across 12 thoracic regions (0-3 per region, total 0-36), while respiratory function changes will be examined via preoperative and 24-hour postoperative spirometry (FVC, FEV₁, FEV₁/FVC). Because postoperative spirometry may be influenced by pain, Numeric Rating Scale (NRS) scores will be recorded to help distinguish true restrictive patterns from pain-limited respiratory effort. The study aims to determine whether ORI-guided FiO₂ titration can reduce postoperative atelectasis and improve respiratory outcomes compared with a fixed FiO₂ approach.

Conditions

Oxygen Reserve Index; Atelectases, Postoperative Pulmonary; Prone Position; Spine Surgery; Lung Ultrasound

Outcome Measures

Primary Outcomes (1)

• Change in Total Lung Ultrasound (LUS) Score

  The primary outcome of the study is the change in the total Lung Ultrasound (LUS) score obtained using a standardized 12-zone lung ultrasound protocol. Each hemithorax was evaluated in six regions-anterior, lateral, and posterior lines, each divided into superior and inferior zones-resulting in a total of 12 assessed areas. Each zone was scored from 0 to 3 based on the degree of aeration, yielding a total score ranging from 0 to 36, with higher scores indicating greater aeration loss and atelectasis. Accordingly, the difference between the preoperative LUS score and the LUS score measured at 30 minutes after extubation was defined as the primary endpoint of the study.

  Baseline (Preoperative) and 30 Minutes After Extubation

Secondary Outcomes (3)

• Change in Forced Vital Capacity (FVC)

  Baseline (Preoperative) and Postoperative 24th Hour

• Change in Forced Expiratory Volume in 1 Second (FEV1)

  Baseline (Preoperative) and Postoperative 24th Hour

• Change in FEV1/FVC Ratio

  Baseline (Preoperative) and Postoperative 24th Hour

Study Arms (2)

Group 1-ORI-Guided FiO₂ Titration Group

ACTIVE COMPARATOR

Patients will receive 80% FiO₂ for 3 minutes before induction. After intubation, FiO₂ will be set to 50% and titrated to keep the Oxygen Reserve Index (ORI) between 0.00-0.05 using the Masimo Rad-97. If ORI ≥0.05 for ≥5 min, FiO₂ will be reduced by 0.05; if ORI stays within 0-0.05 for ≥5 min, FiO₂ will be maintained; if ORI = 0 with SpO₂ \<95%, FiO₂ will be increased by 0.05. The target PaO₂ is 80-120 mmHg. PEEP will be fixed at 5 cmH₂O, and a standard recruitment maneuver will be applied at surgery start. The protocol continues throughout the operation. Only noninvasive methods (ORI, LUS, spirometry) will be used. Both groups will have preoperative LUS and spirometry. Postoperative LUS will be repeated at 30 minutes and spirometry at 24 hours for comparative assessment.

Procedure: Titrated Oxygen

Group 2- Fixed FiO₂

ACTIVE COMPARATOR

Patients will undergo preoxygenation with 80% FiO₂ for 3 minutes prior to induction. After endotracheal intubation, FiO₂ will be maintained at 50% and continued unchanged throughout the surgical procedure. Positive end-expiratory pressure (PEEP) will be set at 5 cmH₂O, and a standard alveolar recruitment maneuver will be applied to all patients at the beginning of surgery. The intervention will be continued throughout the surgical procedure. Only noninvasive monitoring (ORI measurement), lung ultrasonography (LUS), and spirometry will be performed in this study. In both groups, preoperative spirometry and lung ultrasonography will be conducted. Postoperatively, lung ultrasonography will be repeated at the 30th minute, and spirometry will be repeated at the 24th hour to allow for comparative analysis.

Procedure: Fixed oxygen

Interventions

Titrated Oxygen PROCEDURE

This intervention is distinguished by the use of real-time Oxygen Reserve Index (ORI) monitoring to guide individualized intraoperative FiO₂ titration. Unlike fixed-FiO₂ strategies commonly used in anesthesia practice, this protocol continuously adjusts FiO₂ based on ORI values measured with the Masimo Rad-97 device. FiO₂ is increased or decreased in increments of 0.05 according to predefined ORI thresholds to maintain patients within a targeted normoxemic range. The intervention is entirely noninvasive and integrates standardized lung ultrasound (LUS) assessments and spirometry to evaluate postoperative aeration loss and respiratory function. This dynamic, physiology-based oxygen management approach differentiates the intervention from routine fixed-oxygen administration used in other clinical studies.

Also known as: Oxygen Reserve Index-Guided Oxygen Titration

Group 1-ORI-Guided FiO₂ Titration Group

Fixed oxygen PROCEDURE

This intervention uses a standard, non-individualized oxygen administration approach in which FiO₂ is maintained at a constant 50% throughout the entire surgical procedure. After preoxygenation with 80% FiO₂ for 3 minutes, the FiO₂ is set at 0.50 immediately after intubation and is not modified in response to patient physiology or ORI measurements. PEEP is fixed at 5 cmH₂O, and a standardized alveolar recruitment maneuver is applied at the beginning of surgery. This fixed-FiO₂ strategy differs from the ORI-guided titration group by avoiding dynamic oxygen adjustments and reflects conventional intraoperative oxygen management commonly used in clinical practice.

Also known as: fixed 50:50 oxygen and air combination

Group 2- Fixed FiO₂

Eligibility Criteria

• Age: 18 Years - 80 Years
• Sex: all
• Healthy Volunteers: No
• Age Groups: Adult (18-64), Older Adult (65+)

You may qualify if:

• Adults aged 18 to 80 years
• Patients with an ASA physical status of I, II, or III
• Individuals with a body mass index (BMI) between 18 and 35 kg/m²

You may not qualify if:

• History of or active upper or lower respiratory tract infection within the past month
• Pulmonary emphysematous/bullous disease or COPD
• Pre-existing significant atelectasis or consolidation (Preoperative LUS showing a score of 3 consolidation or ≥2 regions with a score ≥2)
• Severe obstructive sleep apnea requiring CPAP therapy
• NYHA class III-IV heart failure, EF \<35%, or severe valvular disease
• Severe arrhythmia or hemodynamic instability requiring high-dose vasopressors
• Body mass index (BMI) \>35 kg/m²
• Severe anemia (Hb \<9 g/dL) or polycythemia (Hb \>18 g/dL)
• Non-diagnostic or unclear preoperative lung ultrasound images
• Preoperative SpO₂ ≤ 94%
• Inability to apply the sensor due to finger deformity, or inadequate signal caused by digital hypoperfusion

Sponsors & Collaborators

• Ankara Etlik City Hospital: lead

MeSH Terms

Conditions

Pulmonary Atelectasis

Interventions

Oxygen

Condition Hierarchy (Ancestors)

Lung Diseases; Respiratory Tract Diseases

Intervention Hierarchy (Ancestors)

Chalcogens; Elements; Inorganic Chemicals; Gases

Study Officials

• Derya Özkan, Professor

  Ankara Etlik City Hospital

  STUDY DIRECTOR

Central Study Contacts

Sıla Soytaş, MD

CONTACT

+905352035289; silasoytas@hotmail.com

Derya Özkan, Professor

CONTACT

+90542 584 36 38; derya_z@yahoo.com

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: NONE
• Purpose: SCREENING
• Intervention Model: PARALLEL
• Sponsor Type: OTHER GOV
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Principal Investigator

Study Record Dates

• First Submitted: November 19, 2025
• First Posted: January 29, 2026
• Study Start: March 15, 2026
• Primary Completion (Estimated): September 30, 2026
• Study Completion (Estimated): November 30, 2026
• Last Updated: January 29, 2026

Record last verified: 2026-01

Data Sharing

• IPD Sharing: Will not share