Apneic OxygenationNCT07415161
Oxygen Reserve Index (ORi) in Identifying Desaturation
A study testing oxygen monitoring techniques in people with Apneic Oxygenation and Endolarengeal Surgery, run by Istanbul University at 1 site in Turkey (Türkiye).
Trial summary
This randomized clinical trial investigates whether Oxygen Reserve Index (ORi) monitoring enables earlier detection of impending hypoxemia compared with conventional pulse oximetry during apneic intermittent ventilation in adult patients undergoing endolaryngeal surgery under general anesthesia. Read more about this study
- Who is it for?
- Ages 18 years and olderHealthy volunteers can take part
- Conditions the study is for
- Apneic Oxygenation, Endolarengeal Surgery, Oxygen Reserve Index
- What is being tested?
- oxygen monitoring techniques
- Type of treatment
- Surgery or procedure
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 80 participants
- Where
- 1 siteTurkey (Türkiye)
- Study dates
- 27 Jan 2026to 25 Mar 2026
- Phase
- Interventional
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 years and older
- All sexes
- Healthy volunteers accepted
- Adult, Older adult
Who may be able to join
- Age 18 years or older
- Scheduled for elective endolaryngeal surgery
- Planned general anesthesia with apneic intermittent ventilation
- American Society of Anesthesiologists (ASA) physical status I-III
- Ability to provide written informed consent
Who cannot join
- Age under 18 years
- Preoperative chronic hypoxemia (baseline SpO₂ < 95%)
- Patients transferred from the intensive care unit
- ASA physical status IV or higher
- Refusal or inability to provide informed consent
Trial locations and contacts
1 site in 1 country. Contact the study team or a site near you to ask about taking part.
Turkey (Türkiye)1 site
Istanbul University, Department of anesthesiology
Istanbul, Fatih, 34093
demet altun, prof, 00905326811767, drdemetaltun@hotmail.com
About this study
Official title: The Role of Oxygen Reserve Index (ORi) in Identifying Early Desaturation During Endolaryngeal Surgery: A Randomized Clinical Trial
This randomized clinical trial investigates whether Oxygen Reserve Index (ORi) monitoring enables earlier detection of impending hypoxemia compared with conventional pulse oximetry during apneic intermittent ventilation in adult patients undergoing endolaryngeal surgery under general anesthesia. By providing continuous, noninvasive assessment of oxygen reserve in the hyperoxic range, ORi may offer an earlier warning of oxygen depletion before peripheral oxygen saturation declines. The study compares time to reventilation thresholds, arterial blood gas parameters, and perioperative respiratory outcomes between ORi-guided and standard SpO₂-guided monitoring strategies.
Read the detailed description
This prospective, single-center, randomized clinical trial was designed to evaluate the role of the Oxygen Reserve Index (ORi) in the early detection of hypoxemia during apneic intermittent ventilation in adult patients undergoing elective endolaryngeal surgery under general anesthesia. Endolaryngeal procedures require shared airway management and frequently involve apneic periods, during which conventional pulse oximetry may fail to provide timely warning of declining oxygen reserves due to the plateau phase of the oxyhemoglobin dissociation curve. Eligible patients aged 18 years and older with ASA physical status I-III were randomly assigned to either an ORi-monitored group or a control group monitored with standard peripheral oxygen saturation (SpO₂). All patients underwent standardized anesthesia induction, preoxygenation, and apneic intermittent ventilation. In the ORi group, the threshold for resuming ventilation was defined as ORi reaching zero, whereas in the control group ventilation was resumed when SpO₂ decreased to 90%. The primary outcome was the time from the onset of apnea to the predefined reventilation threshold. Secondary outcomes included arterial blood gas parameters (pH, PaO₂, PaCO₂) at the time of reventilation, end-tidal carbon dioxide levels, perioperative lung ultrasound findings, post-anesthesia care unit length of stay, and postoperative respiratory outcomes. This study aims to determine whether ORi monitoring provides earlier and clinically meaningful warning of oxygen reserve depletion compared with conventional pulse oximetry, potentially improving patient safety during shared-airway surgery.
- Being tested
- oxygen monitoring techniques
- Keywords
- oxygen reserve index, pulse oximetry, apneic ventilation
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
oxygen monitoring techniquesProcedure or surgery
to determine whether ORi monitoring provides earlier and clinically meaningful warning of oxygen reserve depletion compared with conventional pulse oximetry, potentially improving patient safety during shared-airway surgery.
| Study group | Role | What they receive |
|---|---|---|
| Oxygen Reserve Index | Experimental | Participants in this arm will undergo continuous Oxygen Reserve Index (ORi) monitoring in addition to standard anesthesia monitoring during general anesthesia with apneic intermittent ventilation for endolaryngeal surgery. ORi values will be used to guide the timing of reventilation, with reventilation initiated when ORi reaches zero, indicating depletion of oxygen reserve. Standard clinical care and anesthesia management will otherwise be identical to the control group. Receives: Procedure: oxygen monitoring techniques |
| Peripheral oxygen saturation | No intervention | Participants in this arm will receive standard anesthesia monitoring, including continuous peripheral oxygen saturation (SpO₂) monitoring, during general anesthesia with apneic intermittent ventilation for endolaryngeal surgery. The timing of reventilation will be guided by SpO₂ values, with reventilation initiated when SpO₂ decreases to 90%. All other aspects of anesthesia care and perioperative management will be identical to the experimental arm. |
What is being measured
The primary outcome is the main question the study is designed to answer.
Time to Reventilation Threshold
Time from the onset of apnea to the predefined reventilation threshold, defined as Oxygen Reserve Index (ORi) reaching zero in the ORi group and peripheral oxygen saturation (SpO₂) decreasing to 90% in the control group, measured in seconds.
Measured: From the onset of apnea until the predefined reventilation threshold is reached during the intraoperative period (within minutes).
Secondary outcomes (4)
Arterial Blood Gas Parameters at Reventilation
Arterial blood gas values including pH, partial pressure of oxygen (PaO₂), and partial pressure of carbon dioxide (PaCO₂) measured at the time of reventilation.
Measured: From the onset of apnea until the predefined reventilation threshold is reached during the intraoperative period (within minutes).
Perioperative Lung Ultrasound Findings
Change in lung ultrasound (LUS) B-line count between preoperative and postoperative assessments.
Measured: Preoperatively (before anesthesia induction) and postoperatively in the post-anesthesia care unit (within 1 hour after surgery).
Postoperative Oxygenation
Lowest peripheral oxygen saturation (SpO₂) recorded during PACU stay.
Measured: postoperatively in the post-anesthesia care unit (within 1 hour after surgery).
End-Tidal Carbon Dioxide (EtCO₂) Level
First recorded EtCO₂ value during apnea prior to reventilation.
Measured: During the apneic period, measured at the time of reventilation during surgery.
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted17 Feb 2026
- Study start27 Jan 2026 (estimated)
- Primary completion15 Mar 2026 (estimated)
- Study completion25 Mar 2026 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Publications (2)Papers the sponsor has linked to this study.
- Other trials for Apneic OxygenationStudies of the same condition, open and under way.
- More trials run by Istanbul UniversityThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Model description
- Model Description
- Masking
- Single blind
- Who is masked
- Participant
- Enrolment
- 80 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Istanbul University
- Sponsor type
- University, hospital or other
- Responsible party
- Principal investigator, Demet Altun, Istanbul University
- Investigators
- ece naz demir, resident, Principal investigator, Istanbul Universitydemet altun, prof, Study director, Istanbul University
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07415161
- Sponsor's protocol ID
- 2024/1568
- Status last verified
- Jan 2026
- First submitted
- 27 Jan 2026
- Last updated
- 17 Feb 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
Publications
Fleming NW, Singh A, Lee L, Applegate RL 2nd. Oxygen Reserve Index: Utility as an Early Warning for Desaturation in High-Risk Surgical Patients. Anesth Analg. 2021 Mar 1;132(3):770-776. doi: 10.1213/ANE.0000000000005109.
PubMed 32815872Szmuk P, Steiner JW, Olomu PN, Ploski RP, Sessler DI, Ezri T. Oxygen Reserve Index: A Novel Noninvasive Measure of Oxygen Reserve--A Pilot Study. Anesthesiology. 2016 Apr;124(4):779-84. doi: 10.1097/ALN.0000000000001009.
PubMed 26978143
Study at a glance
From the registry record, last updated by the sponsor on 17 Feb 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- The Role of Oxygen Reserve Index (ORi) in Identifying Early Desaturation During Endolaryngeal Surgery: A Randomized Clinical Trial
- ClinicalTrials.gov ID
- NCT07415161
- Acronym / sponsor ID
- 2024/1568
- Keywords
- oxygen reserve index, pulse oximetry, apneic ventilation
- Study type
- Interventional
- Recruitment status
- Not yet recruiting
- Enrolment
- 80 participants (estimated)
- Lead sponsor
- Istanbul UniversityUniversity, hospital or other
- Study start
- 27 Jan 2026 (estimated)
- Primary completion
- 15 Mar 2026 (estimated)
- Study completion
- 25 Mar 2026 (estimated)
- First posted
- 17 Feb 2026 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
This randomized clinical trial investigates whether Oxygen Reserve Index (ORi) monitoring enables earlier detection of impending hypoxemia compared with conventional pulse oximetry during apneic intermittent ventilation in adult patients undergoing endolaryngeal surgery under general anesthesia. By providing continuous, noninvasive assessment of oxygen reserve in the hyperoxic range, ORi may offer an earlier warning of oxygen depletion before peripheral oxygen saturation declines. The study compares time to reventilation thresholds, arterial blood gas parameters, and perioperative respiratory outcomes between ORi-guided and standard SpO₂-guided monitoring strategies.
Detailed description
This prospective, single-center, randomized clinical trial was designed to evaluate the role of the Oxygen Reserve Index (ORi) in the early detection of hypoxemia during apneic intermittent ventilation in adult patients undergoing elective endolaryngeal surgery under general anesthesia. Endolaryngeal procedures require shared airway management and frequently involve apneic periods, during which conventional pulse oximetry may fail to provide timely warning of declining oxygen reserves due to the plateau phase of the oxyhemoglobin dissociation curve. Eligible patients aged 18 years and older with ASA physical status I-III were randomly assigned to either an ORi-monitored group or a control group monitored with standard peripheral oxygen saturation (SpO₂). All patients underwent standardized anesthesia induction, preoxygenation, and apneic intermittent ventilation. In the ORi group, the threshold for resuming ventilation was defined as ORi reaching zero, whereas in the control group ventilation was resumed when SpO₂ decreased to 90%. The primary outcome was the time from the onset of apnea to the predefined reventilation threshold. Secondary outcomes included arterial blood gas parameters (pH, PaO₂, PaCO₂) at the time of reventilation, end-tidal carbon dioxide levels, perioperative lung ultrasound findings, post-anesthesia care unit length of stay, and postoperative respiratory outcomes. This study aims to determine whether ORi monitoring provides earlier and clinically meaningful warning of oxygen reserve depletion compared with conventional pulse oximetry, potentially improving patient safety during shared-airway surgery.
Study design
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Single blind (participant)
- Number of arms
- 2
- Model description
- Model Description
| Arm | Type | Receives |
|---|---|---|
| Oxygen Reserve Index | Experimental | Procedure: oxygen monitoring techniquesParticipants in this arm will undergo continuous Oxygen Reserve Index (ORi) monitoring in addition to standard anesthesia monitoring during general anesthesia with apneic intermittent ventilation for endolaryngeal surgery. ORi values will be used to guide the timing of reventilation, with reventilation initiated when ORi reaches zero, indicating depletion of oxygen reserve. Standard clinical care and anesthesia management will otherwise be identical to the control group. |
| Peripheral oxygen saturation | No intervention | –Participants in this arm will receive standard anesthesia monitoring, including continuous peripheral oxygen saturation (SpO₂) monitoring, during general anesthesia with apneic intermittent ventilation for endolaryngeal surgery. The timing of reventilation will be guided by SpO₂ values, with reventilation initiated when SpO₂ decreases to 90%. All other aspects of anesthesia care and perioperative management will be identical to the experimental arm. |
Who may qualify
- Ages
- 18 years and older
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (5 listed)
- Age 18 years or older
- Scheduled for elective endolaryngeal surgery
- Planned general anesthesia with apneic intermittent ventilation
- American Society of Anesthesiologists (ASA) physical status I-III
- Ability to provide written informed consent
Key exclusion criteria (5 listed)
- Age under 18 years
- Preoperative chronic hypoxemia (baseline SpO₂ < 95%)
- Patients transferred from the intensive care unit
- ASA physical status IV or higher
- Refusal or inability to provide informed consent
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| oxygen monitoring techniquesto determine whether ORi monitoring provides earlier and clinically meaningful warning of oxygen reserve depletion compared with conventional pulse oximetry, potentially improving patient safety during shared-airway surgery. | Procedure or surgery | Oxygen Reserve Index |
Primary outcome
Time to Reventilation Threshold
Time frame: From the onset of apnea until the predefined reventilation threshold is reached during the intraoperative period (within minutes).
Time from the onset of apnea to the predefined reventilation threshold, defined as Oxygen Reserve Index (ORi) reaching zero in the ORi group and peripheral oxygen saturation (SpO₂) decreasing to 90% in the control group, measured in seconds.
4 secondary outcomes
Arterial Blood Gas Parameters at Reventilation
Time frame: From the onset of apnea until the predefined reventilation threshold is reached during the intraoperative period (within minutes).
Perioperative Lung Ultrasound Findings
Time frame: Preoperatively (before anesthesia induction) and postoperatively in the post-anesthesia care unit (within 1 hour after surgery).
Postoperative Oxygenation
Time frame: postoperatively in the post-anesthesia care unit (within 1 hour after surgery).
End-Tidal Carbon Dioxide (EtCO₂) Level
Time frame: During the apneic period, measured at the time of reventilation during surgery.
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 17 Feb 2026.
- Results publication: PubMed 32815872Fleming NW, Singh A, Lee L, Applegate RL 2nd. Oxygen Reserve Index: Utility as an Early Warning for Desaturation in High-Risk Surgical Patients. Anesth Analg. 2021 Mar 1;132(3):770-776. doi: 10.1213/ANE.0000000000005109.
- Results publication: PubMed 26978143Szmuk P, Steiner JW, Olomu PN, Ploski RP, Sessler DI, Ezri T. Oxygen Reserve Index: A Novel Noninvasive Measure of Oxygen Reserve--A Pilot Study. Anesthesiology. 2016 Apr;124(4):779-84. doi: 10.1097/ALN.0000000000001009.
Related trials for Apneic Oxygenation
Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
ece naz demir, resident principal investigator
Istanbul University
demet altun, prof study director
Istanbul University
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing oxygen monitoring techniques in people with Apneic Oxygenation and Endolarengeal Surgery, run by Istanbul University at 1 site in Turkey (Türkiye).
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 5 inclusion and 5 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: opening soon, as of the sponsor's last update on 17 Feb 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in Turkey (Türkiye). Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Demet Altun, Prof (00905326811767, drdemetaltun@hotmail.com), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Time to Reventilation Threshold (time frame: From the onset of apnea until the predefined reventilation threshold is reached during the intraoperative period (within minutes).). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
On the ClinicalTrials.gov record for NCT07415161, which also lists 2 linked publications.
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 17 Feb 2026; AzTrials last refreshed its copy on 6 Nov 2026.