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

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

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

Interventions

PROCEDURE

Titrated Oxygen

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.

PROCEDURE

Fixed oxygen

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.

Sponsors & Collaborators

• Ankara Etlik City Hospital

  lead OTHER_GOV

Principal Investigators

• Derya Özkan, Professor · Ankara Etlik City Hospital

Study Design

Allocation

RANDOMIZED

Purpose

SCREENING

Masking

NONE

Model

PARALLEL

Eligibility

Min Age

18 Years

Max Age

80 Years

Sex

ALL

Healthy Volunteers

No

Timeline & Regulatory

Start

2026-03-15

Primary Completion

2026-09-30

Completion

2026-11-30