Oxygen Reserve Index-Guided Oxygen Titration During Surgery in the Beach Chair Position (ORI-BCP)

The Utility of Oxygen Reserve Index Guidance in Inspiratory Oxygen Titration for Patients Undergoing Surgery in the Beach Chair Position: A Prospective Comparative Study

This study aims to evaluate whether guidance by the Oxygen Reserve Index (ORi) improves inspiratory oxygen fraction (FiO₂) titration compared with conventional pulse oximetry (SpO₂)-guided oxygen administration in adult patients undergoing surgery in the beach chair position.

Oxygen therapy is routinely used during general anesthesia to prevent hypoxemia; however, excessive oxygen administration may result in hyperoxia, which has been associated with adverse cardiovascular and pulmonary effects. Standard pulse oximetry may not adequately detect hyperoxia when oxygen saturation values are high.

In this prospective comparative study, patients will receive oxygen titration guided either by SpO₂ alone or by combined ORi and SpO₂ monitoring. The primary outcome is the incidence of intraoperative hyperoxemia, assessed by arterial blood gas analysis. Secondary outcomes include intraoperative oxygenation parameters and hemodynamic variables.

Study Overview

• Status: Not yet recruiting
• Conditions: Cerebral Oxygenation; Hyperoxemia; Beach Chair Position; Intraoperative Oxygen Therapy
• Intervention / Treatment: Other: ORi-Guided FiO₂ Titration; Other: SpO₂-Guided FiO₂ Titration

Detailed Description

This prospective study will be conducted in adult patients (ASA physical status I-III) undergoing elective orthopedic surgery in the beach chair position under general anesthesia. Following approval by the institutional ethics committee and acquisition of written informed consent, eligible patients will be included in the study.

Standard monitoring will include electrocardiography, noninvasive blood pressure, peripheral oxygen saturation (SpO₂), bispectral index (BIS), perfusion index (PI), pleth variability index (PVI), near-infrared spectroscopy (NIRS), and multiwavelength pulse co-oximetry for Oxygen Reserve Index (ORi) monitoring. Invasive arterial blood pressure monitoring will be established via radial arterial cannulation to allow continuous hemodynamic monitoring and arterial blood gas sampling.

General anesthesia will be induced with intravenous propofol, fentanyl, and rocuronium, followed by orotracheal intubation. Mechanical ventilation will be applied in volume-controlled mode with lung-protective settings. Anesthesia will be maintained using sevoflurane and remifentanil infusion, targeting bispectral index values between 40 and 60.

From anesthesia induction onward, inspiratory oxygen fraction (FiO₂) will be titrated either according to SpO₂ values alone or using combined ORi and SpO₂ guidance. In the ORi-guided group, FiO₂ adjustments will aim to maintain ORi values between 0.2 and 0.5, with reassessment at regular intervals. In the SpO₂-guided group, FiO₂ will be adjusted to maintain SpO₂ values at or above 98%, in accordance with routine clinical practice.

Hemodynamic parameters, oxygenation variables, ORi values, and cerebral oxygenation assessed by NIRS will be recorded at predefined time points during surgery and recovery. Arterial blood gas analysis will be performed to determine PaO₂ and arterial oxygen saturation.

Hyperoxemia will be defined as a PaO₂ value of 100 mmHg or greater and classified as mild or severe. The primary outcome of the study is the incidence of intraoperative severe hyperoxemia. Secondary outcomes include overall oxygenation profiles and intraoperative hemodynamic stability.

The results of this study are expected to provide evidence regarding the utility of ORi-guided oxygen titration in reducing unnecessary hyperoxia during surgery performed in the beach chair position.

• Study Type: Interventional
• Enrollment (Estimated): 80
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: cagla sancak, md; Phone Number: +90216 578 30 +905064381002; Email: caglasancakk@gmail.com

Study Locations

• Turkey (Türkiye)
  • Istanbul, Turkey (Türkiye), 34000
    • Istanbul Provincial Health Directorate Fatih Sultan Mehmet Training and Research Hospital
    • Contact: cansu ofluoglu, md; Phone Number: +905358640564; Email: cansuakin.iu@gmail.com
    • Contact: cagla sancak, MD; Phone Number: +90 506 438 10 02; Email: caglasancakk@gmail.com

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Adult patients aged 18 to 65 years
• American Society of Anesthesiologists (ASA) physical status I-III
• Scheduled for elective orthopedic surgery in the beach chair position
• Body mass index (BMI) <35 kg/m²
• Ability to provide written informed consent

Exclusion Criteria:

• Age <18 or ≥65 years
• Finger deformities preventing the use of Oxygen Reserve Index (ORi) monitoring
• Severe anemia (hemoglobin <8 g/dL)
• Pregnancy
• Refusal or inability to provide informed consent
• History of stroke or significant vascular pathology
• Severe cardiac or respiratory disease

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Prevention
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: None (Open Label)

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: ORi-Guided FiO₂ Titration; Inspiratory oxygen fraction (FiO₂) will be titrated using combined Oxygen Reserve Index (ORi) and peripheral oxygen saturation (SpO₂) monitoring throughout surgery.	Other: ORi-Guided FiO₂ Titration; Inspiratory oxygen fraction (FiO₂) will be adjusted throughout surgery using combined Oxygen Reserve Index (ORi) and peripheral oxygen saturation (SpO₂) monitoring. FiO₂ will be titrated to maintain ORi values between 0.2 and 0.5, with reassessment every 2-3 minutes.
Active Comparator: SpO₂-Guided Oxygen Titration; Inspiratory oxygen fraction (FiO₂) will be titrated based on peripheral oxygen saturation (SpO₂) values according to routine clinical practice.	Other: SpO₂-Guided FiO₂ Titration; FiO₂ will be adjusted to maintain SpO₂ at or above 98% throughout surgery.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Incidence of Intraoperative Severe Hyperoxemia	Severe hyperoxemia will be defined as an arterial partial pressure of oxygen (PaO2) ≥200 mmHg, measured by arterial blood gas analysis at predefined intraoperative time points.	Perioperative/Periprocedural

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Mean Peripheral Oxygen Saturation (SpO2) During Surgery	Peripheral oxygen saturation (SpO2) measured continuously during surgery using standard pulse oximetry.	Perioperative/Periprocedural
Mean Oxygen Reserve Index (ORi) During Surgery	Oxygen Reserve Index (ORi) values recorded intraoperatively to evaluate oxygenation status.	Perioperative/Periprocedural
Mean Fraction of Inspired Oxygen (FiO₂) During Surgery	Mean fraction of inspired oxygen (FiO₂) expressed as percentage (%), averaged over the surgical period.	Perioperative/Periprocedural
Mean Cerebral Oxygen Saturation Measured by Near-Infrared Spectroscopy During Surgery	Cerebral regional oxygen saturation values measured intraoperatively using near-infrared spectroscopy.	Intraoperative period (from induction of anesthesia to end of surgery)

Collaborators and Investigators

• Sponsor: Fatih Sultan Mehmet Training and Research Hospital
• Investigators: Principal Investigator: cagla sancak, MD, Istanbul Provincial Health Directorate Fatih Sultan Mehmet Training and Research Hospital

Study record dates

Study Major Dates

• Study Start (Estimated): February 15, 2026
• Primary Completion (Estimated): June 30, 2026
• Study Completion (Estimated): July 31, 2026

Study Registration Dates

• First Submitted: January 18, 2026
• First Submitted That Met QC Criteria: February 9, 2026
• First Posted (Actual): February 11, 2026

Study Record Updates

• Last Update Posted (Actual): February 11, 2026
• Last Update Submitted That Met QC Criteria: February 9, 2026
• Last Verified: January 1, 2026

More Information

Terms related to this study

• Keywords: Arterial blood gas; Oxygen Reserve Index; Hyperoxia; Near-infrared spectroscopy; General anesthesia; Pulse oximetry; Orthopedic surgery; Beach chair position; ORİ; FiO2 titration
• Additional Relevant MeSH Terms: Signs and Symptoms, Respiratory; Pathological Conditions, Signs and Symptoms; Signs and Symptoms; Hyperoxia
• Other Study ID Numbers: ORI-FIO2-BCP-2025; 2025/234 (Other Identifier: Sancaktepe Şehit Prof. Dr. İlhan Varank education and research hospital Ethics Committee Approval Number)

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No