Hypoxemia During SurgeryNCT07673042
Effect of Preoxygenation Position and Examination Position on Hypoxemia During Painless Gastrointestinal Endoscopy
A study testing Pre-oxygenation Position （left lateral position）, Examination Position（left lateral position ） and Pre-oxygenation Position（ left lateral head elevation in a 30-degree position） in people with Hypoxemia During Surgery, run by General Hospital of Ningxia Medical University at 1 site in China.
Trial summary
To investigate the independent effects and interaction of pre-oxygenation position (left lateral vs left lateral with 30° head-up tilt) and examination position (left lateral vs left lateral with 30° head-up tilt) on hypoxemia during painless gastroscopy and colonoscopy using a 2×2 factorial design. Read more about this study
- Who is it for?
- Ages 18 to 75 years
- Conditions the study is for
- Hypoxemia During Surgery
- What is being tested?
- Pre-oxygenation Position （left lateral position）, Examination Position（left lateral position ） and Pre-oxygenation Position（ left lateral head elevation in a 30-degree position）
- Type of treatment
- Surgery or procedure
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 208 participants
- Where
- 1 siteChina
- Study dates
- 23 Jun 2026to 31 Aug 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 to 75 years
- All sexes
- No healthy volunteers
- Adult, Older adult
Who may be able to join
- Aged 18 to 75 years, regardless of gender
- Body mass index (BMI): 18.5 - 35 kg/m²
- ASA physical status class I, II or III
- Scheduled for painless gastroscopy, painless colonoscopy, or combined painless gastroenteroscopy
- Able to understand the study procedure and provide written informed consent
Who cannot join
- Severe cardiopulmonary diseases, including severe COPD, heart failure, severe arrhythmia and pulmonary hypertension
- Difficult airway identified before anesthesia
- Severe obstructive sleep apnea (OSA)
- Spinal or thoracic deformity
- Preoperative baseline hypoxemia
- Known allergy to any anesthetic drugs used in this study
- Pregnant females
- Unable to cooperate with required intraoperative body position
Trial locations and contacts
1 site in 1 country. Contact the study team or a site near you to ask about taking part.
China1 site
General hospital of Ningxia medical university
Yinchuan, Ningxia, 750001
xiaoyong wei, Master's degree, 86-951-674-3252, weixy9912@126.cm
About this study
Official title: Effect of Preoxygenation Position and Examination Position on Hypoxemia During Painless Gastrointestinal Endoscopy: A 2×2 Factorial Randomized Controlled Trial
To investigate the independent effects and interaction of pre-oxygenation position (left lateral vs left lateral with 30° head-up tilt) and examination position (left lateral vs left lateral with 30° head-up tilt) on hypoxemia during painless gastroscopy and colonoscopy using a 2×2 factorial design.
Read the detailed description
Painless gastroscopy and colonoscopy represent core minimally invasive techniques for colorectal cancer screening and the diagnosis and treatment of gastrointestinal diseases. By utilizing intravenous sedation to ensure a pain-free experience, these procedures are widely adopted in clinical practice. However, perioperative hypoxemia remains the most common and critical safety complication during sedation for endoscopy. It is primarily caused by anesthesia-induced respiratory depression, tongue base collapse, airway obstruction, diaphragmatic compression, and restricted thoracic movement, with significantly elevated risks observed in obese, elderly, snoring, and short-necked patients.
Hypoxemia may trigger bradycardia, arrhythmias, myocardial ischemia, and cerebral hypoxia. In severe cases, it can lead to apnea, laryngospasm, and forced termination of the procedure, making it a key indicator in endoscopic anesthesia quality control.
Pre-oxygenation is a fundamental measure to increase functional residual capacity (FRC) and prolong the safe apneic time prior to induction, thereby preventing hypoxemia. The examination position directly determines airway patency, mandibular relaxation, diaphragmatic position, and thoracic compliance throughout the procedure. Both are critical, controllable factors regulating perioperative oxygenation. Studies have confirmed that the left lateral position reduces the incidence of hypoxemia, while the left lateral position with 30° head elevation effectively relaxes the mandible, alleviates tongue base collapse, reduces abdominal organ pressure on the diaphragm, and improves ventilation and oxygenation by increasing FRC.
Current research largely focuses on either the pre-oxygenation position or the examination position in isolation, presenting notable limitations: first, the interaction between these two positions has not been evaluated, leaving the synergistic or antagonistic effects of combined interventions unclear; second, there is a lack of efficient validation using a factorial design, which is necessary to simultaneously analyze the main effects and interactions of both independent variables.
Addressing these clinical challenges and research gaps, this study employs a 2×2 factorial randomized controlled design. With pre-oxygenation position and examination position serving as the two intervention factors, the study aims to explore the individual and combined effects of both factors on perioperative hypoxemia. The objective is to identify the optimal positional combination, establish standardized and generalizable positioning protocols for painless endoscopy, accurately reduce the incidence of hypoxemia, enhance the precision of anesthesia management, and provide high-level evidence to guide clinical practice.
- Conditions
- Hypoxemia During Surgery
- Being tested
- Pre-oxygenation Position （left lateral position）, Examination Position（left lateral position ）, Pre-oxygenation Position（ left lateral head elevation in a 30-degree position）, Examination Position（left lateral head elevation in a 30-degree position）
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Pre-oxygenation Position （left lateral position）Procedure or surgery
Also called left lateral position
An angle measuring device is placed beside the head of the examination bed to enable precise adjustment of the head position. Pre-oxygenation phase: Administer pure oxygen via a standardized mask with tight fit, at a flow rate of 6 L/min; instruct the patient to take deep breaths while receiving continuous oxygen for 3 minutes, maintaining the same body position throughout. If the position is altered during this phase, discontinue the procedure. Left lateral pre-oxygenation: The patient assumes a left lateral position on a horizontal bed surface with the head elevated at 0°, supported by pillows to maintain a neutral spine position and avoid excessive neck extension or flexion.
Examination Position（left lateral position ）Procedure or surgery
Also called Left lateral position
Examination Phase: From the initiation of anesthesia and endoscope insertion until completion of the procedure, the patient's position and head-of-bed angle must remain fixed throughout; any adjustments are prohibited during this phase. If the position is altered midway through the examination, the patient will be excluded from the study. Left lateral position examination: The patient assumes a 90-degree left lateral position on a horizontal bed surface with the head of the bed elevated to 0°, supported by pillows to maintain a neutral spinal alignment, avoiding excessive neck extension or flexion.
Pre-oxygenation Position（ left lateral head elevation in a 30-degree position）Procedure or surgery
Also called left lateral head elevation in a 30-degree position
An angle measuring device is placed beside the head of the examination bed to allow precise adjustment of the head position. Pre-oxygenation phase: The patient receives pure oxygen via a standardized mask with tight fit, at a flow rate of 6 L/min; they are instructed to take deep breaths while receiving continuous oxygen for 3 minutes, maintaining the same body position throughout. If the position is altered during this phase, the procedure is discontinued. Left-sided head elevation (30°): During pre-oxygenation, the patient lies in a left lateral position on a horizontal bed surface with the head elevated by 30°, supported by pillows to maintain a neutral spinal alignment and prevent excessive neck extension or flexion.
Examination Position（left lateral head elevation in a 30-degree position）Procedure or surgery
Also called left lateral head elevation in a 30-degree position
Examination Phase: From the initiation of anesthesia and endoscope insertion until completion of the procedure, the patient's position and head-of-bed angle must remain fixed throughout; any adjustments are prohibited during this phase. If the position is altered midway through the examination, the patient will be excluded from the study. Left lateral decubitus examination: The patient assumes a left lateral position on a horizontal bed surface with the head elevated at 30°, supported by a pillow to maintain a neutral spinal alignment, avoiding excessive neck extension or flexion.
| Study group | Role | What they receive |
|---|---|---|
| Group A1B1 (traditional conventional group) | Active comparator | Pre-oxygenated left lateral position + examination in left lateral position Receives: Procedure: Pre-oxygenation Position （left lateral position）; Procedure: Examination Position（left lateral position ） |
| Group A1B2 (improved examination group) | Experimental | Left lateral position with pre-oxygenation + left head elevated 30° during examination Receives: Procedure: Pre-oxygenation Position （left lateral position）; Procedure: Examination Position（left lateral head elevation in a 30-degree position） |
| Group A2B1 (pre-oxygenation improvement group) | Experimental | Left-sided head position at 30°, pre-oxygenated air administration + examination in left lateral decubitus position Receives: Procedure: Examination Position（left lateral position ）; Procedure: Pre-oxygenation Position（ left lateral head elevation in a 30-degree position） |
| Group A2B2 (double-position improvement group) | Experimental | Left-sided head height at 30 weeks: pre-oxygenated condition + left-sided head height at 30 weeks examination Receives: Procedure: Pre-oxygenation Position（ left lateral head elevation in a 30-degree position）; Procedure: Examination Position（left lateral head elevation in a 30-degree position） |
What is being measured
The primary outcome is the main question the study is designed to answer.
Incidence of hypoxemia
Incidence of SpO₂ ≤ 90% for >10 seconds during the examination.
Measured: During procedure
Secondary outcomes (12)
Safe duration of pre-oxygenation
Time from cessation of oxygen administration (start of anesthesia induction) to first SpO₂ <92% for ≥3 seconds. If no desaturation occurs, the value equals the duration from oxygen cessation to end of procedure (right-censored).
Measured: During procedure
Incidence of subclinical respiratory depression
Defined as the proportion of participants experiencing SpO₂ between 90% and 95% (inclusive) at any time during the examination.
Measured: During procedure
Requirement for jaw thrust
Number of participants requiring manual jaw thrust to relieve airway obstruction during the examination.
Measured: During procedure
Requirement for nasal cannula oxygen
Number of participants requiring oxygen supplementation via nasal cannula during the examination.
Measured: During procedure
Requirement for increased oxygen flow
Number of participants requiring an increase in oxygen flow rate during the examination.
Measured: During procedure
Requirement for mask ventilation
Number of participants requiring bag-mask ventilation during the examination.
Measured: During procedure
Requirement for endotracheal intubation
Number of participants requiring endotracheal intubation during the examination.
Measured: During procedure
Incidence of airway intervention
Proportion of participants requiring any airway intervention (jaw thrust, nasal cannula, increased flow, mask ventilation, or intubation)
Measured: During procedure
Severity of coughing
Assessed using a 4-grade scale: Grade I (none), Grade II (single mild episode), Grade III (multiple episodes <15s), Grade IV (continuous >15s)
Measured: During procedure
Length of stay in recovery room
Time from arrival to discharge from the recovery room (maximum observation 30 minutes)
Measured: Up to 30 minutes post-anesthesia care unit (PACU) admission
Endoscopist satisfaction score
Assessed using a Numerical Rating Scale (NRS) ranging from 0 to 10, with higher scores indicating greater satisfaction.
Measured: During procedure
Incidence of postoperative nausea, vomiting, headache, and dizziness
Proportion of participants experiencing nausea, vomiting, headache, or dizziness after awakening in the recovery room.
Measured: Up to 30 minutes post-anesthesia care unit (PACU) admission
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted29 Jun 2026
- Study start23 Jun 2026 (estimated)
- Primary completion31 Jul 2026 (estimated)
- Study completion31 Aug 2026 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Hypoxemia During SurgeryStudies of the same condition, open and under way.
- 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
- Prevention
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Single blind
- Who is masked
- Participant
- Enrolment
- 208 participants (estimated)
Sponsor and investigators
- Lead sponsor
- General Hospital of Ningxia Medical University
- Sponsor type
- University, hospital or other
- Responsible party
- Sponsor
- Investigators
- Xinli Ni, Doctoral, Study chair, General Hospital of Ningxia Medical University
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07673042
- Sponsor's protocol ID
- dywe0003
- Status last verified
- Jun 2026
- First submitted
- 15 Jun 2026
- Last updated
- 29 Jun 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No
Study at a glance
From the registry record, last updated by the sponsor on 29 Jun 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Effect of Preoxygenation Position and Examination Position on Hypoxemia During Painless Gastrointestinal Endoscopy: A 2×2 Factorial Randomized Controlled Trial
- ClinicalTrials.gov ID
- NCT07673042
- Acronym / sponsor ID
- dywe0003
- Conditions
- Hypoxemia During Surgery
- Study type
- Interventional
- Recruitment status
- Not yet recruiting
- Enrolment
- 208 participants (estimated)
- Lead sponsor
- General Hospital of Ningxia Medical UniversityUniversity, hospital or other
- Study start
- 23 Jun 2026 (estimated)
- Primary completion
- 31 Jul 2026 (estimated)
- Study completion
- 31 Aug 2026 (estimated)
- First posted
- 29 Jun 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.
To investigate the independent effects and interaction of pre-oxygenation position (left lateral vs left lateral with 30° head-up tilt) and examination position (left lateral vs left lateral with 30° head-up tilt) on hypoxemia during painless gastroscopy and colonoscopy using a 2×2 factorial design.
Detailed description
Painless gastroscopy and colonoscopy represent core minimally invasive techniques for colorectal cancer screening and the diagnosis and treatment of gastrointestinal diseases. By utilizing intravenous sedation to ensure a pain-free experience, these procedures are widely adopted in clinical practice. However, perioperative hypoxemia remains the most common and critical safety complication during sedation for endoscopy. It is primarily caused by anesthesia-induced respiratory depression, tongue base collapse, airway obstruction, diaphragmatic compression, and restricted thoracic movement, with significantly elevated risks observed in obese, elderly, snoring, and short-necked patients.
Hypoxemia may trigger bradycardia, arrhythmias, myocardial ischemia, and cerebral hypoxia. In severe cases, it can lead to apnea, laryngospasm, and forced termination of the procedure, making it a key indicator in endoscopic anesthesia quality control.
Pre-oxygenation is a fundamental measure to increase functional residual capacity (FRC) and prolong the safe apneic time prior to induction, thereby preventing hypoxemia. The examination position directly determines airway patency, mandibular relaxation, diaphragmatic position, and thoracic compliance throughout the procedure. Both are critical, controllable factors regulating perioperative oxygenation. Studies have confirmed that the left lateral position reduces the incidence of hypoxemia, while the left lateral position with 30° head elevation effectively relaxes the mandible, alleviates tongue base collapse, reduces abdominal organ pressure on the diaphragm, and improves ventilation and oxygenation by increasing FRC.
Current research largely focuses on either the pre-oxygenation position or the examination position in isolation, presenting notable limitations: first, the interaction between these two positions has not been evaluated, leaving the synergistic or antagonistic effects of combined interventions unclear; second, there is a lack of efficient validation using a factorial design, which is necessary to simultaneously analyze the main effects and interactions of both independent variables.
Addressing these clinical challenges and research gaps, this study employs a 2×2 factorial randomized controlled design. With pre-oxygenation position and examination position serving as the two intervention factors, the study aims to explore the individual and combined effects of both factors on perioperative hypoxemia. The objective is to identify the optimal positional combination, establish standardized and generalizable positioning protocols for painless endoscopy, accurately reduce the incidence of hypoxemia, enhance the precision of anesthesia management, and provide high-level evidence to guide clinical practice.
Study design
- Primary purpose
- Prevention
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Single blind (participant)
- Number of arms
- 4
| Arm | Type | Receives |
|---|---|---|
| Group A1B1 (traditional conventional group) | Active comparator | Procedure: Pre-oxygenation Position （left lateral position）, Procedure: Examination Position（left lateral position ）Pre-oxygenated left lateral position + examination in left lateral position |
| Group A1B2 (improved examination group) | Experimental | Procedure: Pre-oxygenation Position （left lateral position）, Procedure: Examination Position（left lateral head elevation in a 30-degree position）Left lateral position with pre-oxygenation + left head elevated 30° during examination |
| Group A2B1 (pre-oxygenation improvement group) | Experimental | Procedure: Examination Position（left lateral position ）, Procedure: Pre-oxygenation Position（ left lateral head elevation in a 30-degree position）Left-sided head position at 30°, pre-oxygenated air administration + examination in left lateral decubitus position |
| Group A2B2 (double-position improvement group) | Experimental | Procedure: Pre-oxygenation Position（ left lateral head elevation in a 30-degree position）, Procedure: Examination Position（left lateral head elevation in a 30-degree position）Left-sided head height at 30 weeks: pre-oxygenated condition + left-sided head height at 30 weeks examination |
Who may qualify
- Ages
- 18 to 75 years
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (5 listed)
- Aged 18 to 75 years, regardless of gender
- Body mass index (BMI): 18.5 - 35 kg/m²
- ASA physical status class I, II or III
- Scheduled for painless gastroscopy, painless colonoscopy, or combined painless gastroenteroscopy
- Able to understand the study procedure and provide written informed consent
Key exclusion criteria (8 listed)
- Severe cardiopulmonary diseases, including severe COPD, heart failure, severe arrhythmia and pulmonary hypertension
- Difficult airway identified before anesthesia
- Severe obstructive sleep apnea (OSA)
- Spinal or thoracic deformity
- Preoperative baseline hypoxemia
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 |
|---|---|---|
| Pre-oxygenation Position （left lateral position）Also: left lateral positionAn angle measuring device is placed beside the head of the examination bed to enable precise adjustment of the head position. Pre-oxygenation phase: Administer pure oxygen via a standardized mask with tight fit, at a flow rate of 6 L/min; instruct the patient to take deep breaths while receiving continuous oxygen for 3 minutes, maintaining the same body position throughout. If the position is altered during this phase, discontinue the procedure. Left lateral pre-oxygenation: The patient assumes a left lateral position on a horizontal bed surface with the head elevated at 0°, supported by pillows to maintain a neutral spine position and avoid excessive neck extension or flexion. | Procedure or surgery | Group A1B1 (traditional conventional group), Group A1B2 (improved examination group) |
| Examination Position（left lateral position ）Also: Left lateral positionExamination Phase: From the initiation of anesthesia and endoscope insertion until completion of the procedure, the patient's position and head-of-bed angle must remain fixed throughout; any adjustments are prohibited during this phase. If the position is altered midway through the examination, the patient will be excluded from the study. Left lateral position examination: The patient assumes a 90-degree left lateral position on a horizontal bed surface with the head of the bed elevated to 0°, supported by pillows to maintain a neutral spinal alignment, avoiding excessive neck extension or flexion. | Procedure or surgery | Group A1B1 (traditional conventional group), Group A2B1 (pre-oxygenation improvement group) |
| Pre-oxygenation Position（ left lateral head elevation in a 30-degree position）Also: left lateral head elevation in a 30-degree positionAn angle measuring device is placed beside the head of the examination bed to allow precise adjustment of the head position. Pre-oxygenation phase: The patient receives pure oxygen via a standardized mask with tight fit, at a flow rate of 6 L/min; they are instructed to take deep breaths while receiving continuous oxygen for 3 minutes, maintaining the same body position throughout. If the position is altered during this phase, the procedure is discontinued. Left-sided head elevation (30°): During pre-oxygenation, the patient lies in a left lateral position on a horizontal bed surface with the head elevated by 30°, supported by pillows to maintain a neutral spinal alignment and prevent excessive neck extension or flexion. | Procedure or surgery | Group A2B1 (pre-oxygenation improvement group), Group A2B2 (double-position improvement group) |
| Examination Position（left lateral head elevation in a 30-degree position）Also: left lateral head elevation in a 30-degree positionExamination Phase: From the initiation of anesthesia and endoscope insertion until completion of the procedure, the patient's position and head-of-bed angle must remain fixed throughout; any adjustments are prohibited during this phase. If the position is altered midway through the examination, the patient will be excluded from the study. Left lateral decubitus examination: The patient assumes a left lateral position on a horizontal bed surface with the head elevated at 30°, supported by a pillow to maintain a neutral spinal alignment, avoiding excessive neck extension or flexion. | Procedure or surgery | Group A1B2 (improved examination group), Group A2B2 (double-position improvement group) |
Primary outcome
Incidence of hypoxemia
Time frame: During procedure
Incidence of SpO₂ ≤ 90% for >10 seconds during the examination.
12 secondary outcomes
Safe duration of pre-oxygenation
Time frame: During procedure
Incidence of subclinical respiratory depression
Time frame: During procedure
Requirement for jaw thrust
Time frame: During procedure
Requirement for nasal cannula oxygen
Time frame: During procedure
Requirement for increased oxygen flow
Time frame: During procedure
Requirement for mask ventilation
Time frame: During procedure
Requirement for endotracheal intubation
Time frame: During procedure
Incidence of airway intervention
Time frame: During procedure
Severity of coughing
Time frame: During procedure
Length of stay in recovery room
Time frame: Up to 30 minutes post-anesthesia care unit (PACU) admission
Endoscopist satisfaction score
Time frame: During procedure
Incidence of postoperative nausea, vomiting, headache, and dizziness
Time frame: Up to 30 minutes post-anesthesia care unit (PACU) admission
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 29 Jun 2026.
- Individual participant dataSharing planned: No
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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.
Xinli Ni, Doctoral study chair
General Hospital of Ningxia Medical 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 Pre-oxygenation Position （left lateral position）, Examination Position（left lateral position ） and Pre-oxygenation Position（ left lateral head elevation in a 30-degree position） in people with Hypoxemia During Surgery, run by General Hospital of Ningxia Medical University at 1 site in China.
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 8 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 29 Jun 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 China. 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 xiaoyong wei, Master's degree (86-951-674-3252, weixy9912@126.com), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Incidence of hypoxemia (time frame: During procedure). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
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 29 Jun 2026.