Effect of Different Body Positions on Hypoxemia During Recovery in Patients Undergoing Painless Gastroscopy and Colonoscopy

Effects of Lateral Decubitus Head-up Position, Supine Head-up Position, and Standard Lateral Decubitus Position on Hypoxemia During Recovery in Patients Undergoing Painless Gastroscopy and Colonoscopy: A Multicenter, Three-arm Randomized Controlled Trial

Through a multicenter, three-arm randomized controlled trial design, this study aimed to compare the effects of three positioning strategies-side-lying with elevated head position, supine with elevated head position, and standard side-lying position-on the incidence of hypoxemia during the recovery phase in patients undergoing painless gastroscopy and colonoscopy. The goal was to provide clinicians with a simple, non-invasive, and cost-effective optimization strategy.

Study Overview

• Status: Recruiting
• Conditions: Postoperative Hypoxemia
• Intervention / Treatment: Procedure: supine head-up position (SH group); Procedure: standard lateral decubitus position group (SL group); Procedure: lateral decubitus head-up position (LH group)

Detailed Description

Painless gastroscopy and colonoscopy have become the gold standard for screening and diagnosing gastrointestinal diseases due to their high patient comfort and excellent compliance rates, with their clinical application expanding annually. This procedure is performed under intravenous general anesthesia to achieve painlessness; however, anesthetic agents exert inhibitory effects on the patient's respiratory center. Additionally, the procedural manipulation causes irritation to the airways and gastrointestinal tract, leading to a high incidence of hypoxemia during the postoperative recovery phase-the most common respiratory adverse event associated with painless gastroscopy and colonoscopy. Mild cases may prolong patient recovery time, while severe cases can result in serious complications such as hypoxic brain injury or cardiac arrest, directly compromising patient safety and healthcare experience.

Positioning is a critical non-pharmacological intervention factor influencing perioperative respiratory function in patients undergoing painless gastroscopy and colonoscopy. Different positions alter thoracic compliance, airway patency, and diaphragmatic position, thereby affecting the patient's ventilation and oxygenation status. Currently, the standard lateral decubitus position is routinely used for painless gastroscopy and colonoscopy, and it has been demonstrated to reduce the incidence of hypoxemia. However, this position presents challenges such as difficulties in patient monitoring and localized pressure-related discomfort. In contrast, the supine head-up and lateral decubitus head-up positions, by elevating the head and adjusting the body angle, effectively mitigate tongue base prolapse and improve thoracic expansion, theoretically reducing the risk of hypoxemia. Nevertheless, there is currently a lack of multicenter, large-sample, prospective randomized controlled studies to compare the efficacy and safety of these three positions in preventing hypoxemia in recovery rooms for painless gastroscopy and colonoscopy patients. Consequently, there is no unified evidence-based guideline for selecting the optimal clinical positioning.

Based on this, this study focuses on three clinically common positions and employs a multicenter, three-arm, randomized controlled parallel design to systematically investigate the effects of lateral supine with head elevated, supine with head elevated, and standard lateral position on postoperative hypoxemia in patients undergoing painless gastroscopy and colonoscopy. The aim is to fill a research gap in this field and provide high-quality evidence-based medical data to optimize postoperative position management during recovery and reduce adverse respiratory events following painless gastrointestinal endoscopy.

Special Note：Prespecified subgroup analyses will be conducted based on age (<65 vs ≥65), sex, BMI, ASA class, smoking and alcohol use, Mallampati score, anesthetic agent (clobupol or propofol), type of endoscopy (gastroscopy, colonoscopy, or gastroenteroscopy), Ramsay sedation score (2-4), pre-procedure hypoxemia, prior pulmonary surgery, OSA, respiratory disease, and intra-procedural hypoxemia (SpO₂ ≤90% for >10 seconds). The influence of heterogeneity on the primary outcome will also be evaluated.

• Study Type: Interventional
• Enrollment (Estimated): 1617
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: xiaoyong wei, Master's degree; Phone Number: 86-951-674-3252; Email: weixy9912@126.com

Study Locations

• China
  • Ningxia
    • Yinchuan, Ningxia, China, 750001
      • Recruiting
      • General hospital of Ningxia medical university, Yinchuan, Ningxia
      • Contact: xiaoyong wei; Phone Number: 86-951-674-3252; Email: weixy9912@126.cm

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

1. Age ≥ 18 years.
2. Both sexes.
3. American Society of Anesthesiologists (ASA) physical status classification I-III.
4. Scheduled for combined painless esophagogastroduodenoscopy/colonoscopy or either of the two procedures.
5. Ability to understand the study protocol and provide written informed consent.
6. A broad set of inclusion criteria was adopted to enroll a patient population that better reflects routine clinical practice. The study aimed to enhance the generalizability of the findings by including patients with various comorbidities, such as preprocedural hypoxemia (room-air SpO₂ ≤ 90%), history of pulmonary surgery, obstructive sleep apnea (OSA), and other pulmonary conditions (including asthma, COPD, chronic bronchitis, emphysema, and pulmonary bullae).

Exclusion Criteria:

1. Severe cardiovascular or cerebrovascular diseases.
2. Pregnant patients.
3. History of hypersensitivity to ciprofol.

Withdrawal Criteria:

1. Endotracheal intubation required during the procedure.
2. Voluntary withdrawal requested by the patient or their legal representative.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Single

Number of Arms

3

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: lateral decubitus head-up position group (LH group); The patient maintains the predetermined lateral position with the head of the bed elevated at 30 degrees.	Procedure: supine head-up position (SH group); An angle measuring device is placed beside the head of the examination bed to facilitate precise adjustment of the head position. Upon admission to the recovery room, the patient's Ramsay Sedation Scale score is assessed by an independent investigator (the attending anesthesiologist): 1 = agitated; 2 = fully awake, calm and cooperative; 3 = drowsy but responsive to verbal commands; 4 = drowsy but responsive to tactile or pain stimuli; 5 = asleep but slow to tactile or pain responses; 6 = deep sleep with no response. Patients scoring 2-4 are immediately randomized into the study group, while those below this range are randomized after achieving the required score. All patients are initially positioned in the left lateral decubitus position (head elevated at 0°, the same as during examination). Patients assigned to the supine head-elevated group (SH group) are transitioned from the lateral position to supine without a headrest, with the head elevated at 30°.; Procedure: standard lateral decubitus position group (SL group); An angle measuring device was placed beside the head of the examination bed to facilitate precise adjustment of the head position. Upon admission to the recovery room, the patient's Ramsay Sedation Scale was assessed by an independent investigator (the attending anesthesiologist): 1 = agitated; 2 = fully awake, calm and cooperative; 3 = drowsy but responsive to verbal commands; 4 = drowsy but responsive to touch or pain; 5 = asleep but slow to respond to touch or pain; 6 = deep sleep with no response. Patients scoring 2-4 were immediately randomized into the study group, while those below this range were randomized after achieving the required score. All patients were initially positioned in the left lateral decubitus position (head elevated at 0°, the same as during examination). Patients in the Standard Lateral Position Group (SL group) maintained their original left lateral position with the head elevated at 0°.
Experimental: supine head-up position group (SH group); The patient was transferred from a pre-existing lateral decubitus position to a supine position without a headrest, with the head of the bed elevated at 30 degrees.	Procedure: standard lateral decubitus position group (SL group); An angle measuring device was placed beside the head of the examination bed to facilitate precise adjustment of the head position. Upon admission to the recovery room, the patient's Ramsay Sedation Scale was assessed by an independent investigator (the attending anesthesiologist): 1 = agitated; 2 = fully awake, calm and cooperative; 3 = drowsy but responsive to verbal commands; 4 = drowsy but responsive to touch or pain; 5 = asleep but slow to respond to touch or pain; 6 = deep sleep with no response. Patients scoring 2-4 were immediately randomized into the study group, while those below this range were randomized after achieving the required score. All patients were initially positioned in the left lateral decubitus position (head elevated at 0°, the same as during examination). Patients in the Standard Lateral Position Group (SL group) maintained their original left lateral position with the head elevated at 0°.; Procedure: lateral decubitus head-up position (LH group); An angle measuring device is placed beside the head of the examination bed to facilitate precise adjustment of the head position. Upon admission to the recovery room, the patient's Ramsay Sedation Scale score is assessed by an independent investigator (the attending anesthesiologist): 1 = agitated; 2 = fully awake, calm and cooperative; 3 = drowsy but responsive to verbal commands; 4 = drowsy but responsive to touch or pain; 5 = asleep but slow to respond to touch or pain; 6 = deep sleep with no response. Patients scoring 2-4 are immediately randomized into the study group, while those below this range are randomized after achieving the required score. Prior to enrollment, all patients remain in the left lateral position (bed head elevated 0°, consistent with the examination position). Patients assigned to the lateral supine head-elevated group (LH group) maintain their pre-assigned lateral position with the head elevated 30°.
Experimental: standard lateral decubitus position group (SL group); Patients should maintain their original left lateral position with the head of the bed elevated at 0 degrees.	Procedure: supine head-up position (SH group); An angle measuring device is placed beside the head of the examination bed to facilitate precise adjustment of the head position. Upon admission to the recovery room, the patient's Ramsay Sedation Scale score is assessed by an independent investigator (the attending anesthesiologist): 1 = agitated; 2 = fully awake, calm and cooperative; 3 = drowsy but responsive to verbal commands; 4 = drowsy but responsive to tactile or pain stimuli; 5 = asleep but slow to tactile or pain responses; 6 = deep sleep with no response. Patients scoring 2-4 are immediately randomized into the study group, while those below this range are randomized after achieving the required score. All patients are initially positioned in the left lateral decubitus position (head elevated at 0°, the same as during examination). Patients assigned to the supine head-elevated group (SH group) are transitioned from the lateral position to supine without a headrest, with the head elevated at 30°.; Procedure: lateral decubitus head-up position (LH group); An angle measuring device is placed beside the head of the examination bed to facilitate precise adjustment of the head position. Upon admission to the recovery room, the patient's Ramsay Sedation Scale score is assessed by an independent investigator (the attending anesthesiologist): 1 = agitated; 2 = fully awake, calm and cooperative; 3 = drowsy but responsive to verbal commands; 4 = drowsy but responsive to touch or pain; 5 = asleep but slow to respond to touch or pain; 6 = deep sleep with no response. Patients scoring 2-4 are immediately randomized into the study group, while those below this range are randomized after achieving the required score. Prior to enrollment, all patients remain in the left lateral position (bed head elevated 0°, consistent with the examination position). Patients assigned to the lateral supine head-elevated group (LH group) maintain their pre-assigned lateral position with the head elevated 30°.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Incidence of recovery-phase hypoxemia	Proportion of participants experiencing hypoxemia (SpO₂ ≤ 90% lasting >10 seconds) during the post-procedure recovery period	From PACU admission until discharge, assessed up to 30 minutes

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Overall Incidence of Airway Intervention During Recovery	Proportion of participants requiring any grade of airway intervention (increase oxygen flow, chin lift, mask ventilation, or reintubation) during recovery.	From PACU admission until discharge, assessed up to 30 minutes
Respiratory Comfort Score During Recovery	Patient-reported respiratory comfort assessed using a Numerical Rating Scale (NRS) ranging from 0 (worst discomfort) to 10 (greatest comfort)	From PACU admission until discharge, assessed up to 30 minutes
Incidence of Tachycardia During Recovery	Proportion of participants experiencing tachycardia (heart rate >100 beats/min) during the post-procedure recovery period.	From PACU admission until discharge, assessed up to 30 minutes
Incidence of Bradycardia During Recovery	Proportion of participants experiencing bradycardia (heart rate <50 beats/min) during recovery.	From PACU admission until discharge, assessed up to 30 minutes
Incidence of Hypotension During Recovery	Proportion of participants experiencing hypotension (systolic blood pressure <80 mmHg) during recovery.	From PACU admission until discharge, assessed up to 30 minutes
Incidence of Nausea or Vomiting During Recovery	Proportion of participants experiencing nausea (subjective complaint) or vomiting (objective expulsion of gastric contents) during recovery.	From PACU admission until discharge, assessed up to 30 minutes
Incidence of Laryngospasm During Recovery	Proportion of participants experiencing laryngospasm (acute upper airway obstruction with stridor/inability to ventilate, resolving with intervention) during recovery.	From PACU admission until discharge, assessed up to 30 minutes
Incidence of Subclinical Respiratory Depression during Recovery	Proportion of participants experiencing subclinical respiratory depression, defined as any episode of pulse oxygen saturation (SpO₂) in the range of 90% to <95% (inclusive of 90%, exclusive of 95%) during the post-procedure recovery period	From PACU admission until discharge, assessed up to 30 minutes.
Cough Severity Grade During Recovery	Severity of cough assessed during the recovery period, graded as: Grade I: No cough, smooth breathing; Grade II: Single mild cough; Grade III: Multiple coughs lasting <15 seconds; Grade IV: Continuous coughing lasting ≥15 seconds. Reported as the proportion of participants reaching each grade (I-IV).	From PACU admission until discharge, assessed up to 30 minutes
Length of Stay in Post-Anesthesia Care Unit (PACU)	Time from admission to the post-anesthesia care unit (PACU) until discharge criteria are met (modified Aldrete score ≥9 on three consecutive assessments), recorded in minutes.	From PACU admission until discharge, assessed up to 30 minutes
PACU Nurse Satisfaction Score	Nurse-assessed satisfaction with patient respiratory stability and overall recovery management, rated using a Numerical Rating Scale (NRS) ranging from 0 (lowest satisfaction) to 10 (highest satisfaction), recorded at patient discharge from the post-anesthesia care unit	From PACU admission until discharge, assessed up to 30 minutes

Collaborators and Investigators

• Sponsor: General Hospital of Ningxia Medical University
• Collaborators: Wuzhong City People's Hospital; Yinchuan Traditional Chinese Medicine Hospital; Guyuan Municipal People's Hospital; Zhongwei City People's Hospital; Shizuishan City People's Hospital; Zhongwei City Traditional Chinese Medicine Hospital; Pingluo County People's Hospital; Tongxin County People's Hospital; Yanchi County People's Hospital; Zhongning County People's Hospital; Lingwu City People's Hospital; Qingtongxia City People's Hospital
• Investigators: Study Chair: Xinli Ni, Doctoral, 86-951-674-3252

Study record dates

Study Major Dates

• Study Start (Estimated): May 12, 2026
• Primary Completion (Estimated): December 31, 2026
• Study Completion (Estimated): January 31, 2027

Study Registration Dates

• First Submitted: May 1, 2026
• First Submitted That Met QC Criteria: May 7, 2026
• First Posted (Actual): May 14, 2026

Study Record Updates

• Last Update Posted (Actual): May 14, 2026
• Last Update Submitted That Met QC Criteria: May 7, 2026
• Last Verified: May 1, 2026

More Information

Terms related to this study

• Other Study ID Numbers: dywe0002

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

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