Evaluation of Oxygen Reserve Index (ORi) in Obese and Non-Obese Patients Over 65 Years Old

June 30, 2026 updated by: Çağla TUNCEL, Ankara City Hospital Bilkent

Evaluation of Oxygen Reserve Index (ORi) in Obese and Non-Obese Patients Over 65 Years Old Scheduled for Elective Surgery Under General Anesthesia

After obtaining ethical committee approval, this single-center, prospective, observational study included volunteer patients of both sexes, aged 65 years and older, with ASA II-III risk scores, who were scheduled for elective surgery with endotracheal intubation under general anesthesia (GAA). 90 patients were divided into two groups: those with normal BMI (19 < BMI < 25 kg/m² (GROUP 1)) and those who were obese (30 < BMI < 40 kg/m² (GROUP 2)). In addition to standard ASA monitoring, a finger sensor (Rainbow® SET, Masimo Inc., Irvine, Ca., USA) was implanted for ORi measurement, and baseline values were recorded. Patients were preoxygenated until EtO2 (endtidal oxygen) concentration reached at least 85%. After ORi reached a plateau level, general anesthesia was induced and endotracheal intubation was performed. After confirming the tube's position, the breathing circuit was disconnected from the endotracheal tube, and patients were allowed to be apneic until SpO2 reached 94%. Throughout this process, patients' other vital signs, SpO₂, and ORi were continuously monitored. The time elapsed when ORi triggered an alarm, when SpO2 reached 97%, and when SpO2 reached 94% was recorded. The 'ORi warning time', 'SpO2 warning time', and the 'additional warning time provided by ORi' (the difference between 'ORi warning time' and 'SpO2 warning time') were recorded.

Study Overview

Status

Completed

Conditions

Study Type

Observational

Enrollment (Actual)

90

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Older Adult

Accepts Healthy Volunteers

Yes

Sampling Method

Non-Probability Sample

Study Population

90 patients aged 65 and over, ASA II-III

Description

Inclusion Criteria:

Patients of both sexes aged 65 years and older with ASA II-III risk scores who are scheduled to undergo elective surgical procedures with endotracheal intubation under general anesthesia.

Exclusion Criteria:

  • Patients under 65 years of age
  • Patients with heart and lung disease
  • Patients in situations where the patient is unable to cooperate (e.g., dementia, Alzheimer's)
  • Patients suspected of having airway difficulties

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

Cohorts and Interventions

Group / Cohort
Group 1
Patients with normal BMI (19 < BMI < 25 kg/m²)
Group 2
Obese patients (30 < BMI < 40 kg/m² )

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Oxygen reserve index (ORi) warning time, SpO2 warning time, and added warning time defined as the difference between the two
Time Frame: 15 minutes after preoxygenation
The primary aim of this study was to determine whether ORi provides an early warning of impending desaturation compared to pulse oximetry in both obese (30 < BMI < 40 kg/m²) and normal body mass index (19 < BMI < 25 kg/m²) patients over 65 years of age scheduled for elective surgery will be assesed until SpO2 drops to 94%
15 minutes after preoxygenation

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Oxygen reserve index (ORi) warning time, SpO2 warning time, and added warning time defined as the difference between the two
Time Frame: 15 minutes after preoxygenation
The secondary objective of this study was to compare the additional stimulus duration provided by ORi in obese (30 < BMI < 40 kg/m²) and normal body mass index (19 < BMI < 25 kg/m²) patients over 65 years of age will be assesed until SpO2 drops to 94%
15 minutes after preoxygenation

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Ankara City Hospital Bilkent

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

November 1, 2023

Primary Completion (Actual)

May 1, 2024

Study Completion (Actual)

July 1, 2024

Study Registration Dates

First Submitted

May 2, 2026

First Submitted That Met QC Criteria

June 30, 2026

First Posted (Actual)

July 1, 2026

Study Record Updates

Last Update Posted (Actual)

July 1, 2026

Last Update Submitted That Met QC Criteria

June 30, 2026

Last Verified

June 1, 2026

More Information

Terms related to this study

Additional Relevant MeSH Terms

Other Study ID Numbers

  • AnkaraCHBilkent-AR-CT-01

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

IPD Plan Description

I will share the parameters and results of the study.

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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