Effect of Lateral Versus Supine Positions on Postoperative Hypoxemia

Effect of Lateral Versus Supine Positions on Postoperative Hypoxemia in Patients Undergoing Painless Gastroscopy and Colonoscopy: A Prospective Randomized Controlled Study

Using prospective real-world data, this study aims to determine whether the lateral decubitus position reduces the incidence of post-procedure hypoxemia in patients undergoing painless gastroscopy/colonoscopy, thereby providing a simple, non-invasive, and low-cost optimization strategy for clinical practice.

Study Overview

• Status: Recruiting
• Conditions: Postoperative Hypoxemia
• Intervention / Treatment: Procedure: Supine position group (Group S); Procedure: Lateral decubitus position group (Group L)

Detailed Description

Painless gastroscopy and colonoscopy have become essential modalities for the screening and diagnosis of digestive tract diseases, with their utilization increasing annually. However, hypoxemia remains the most common complication during these procedures, with reported incidences ranging widely from 1.8% to 69%. Severe hypoxemia can lead to adverse outcomes, including arrhythmias, hemodynamic decompensation, and hypoxic brain injury. Consequently, developing effective strategies to prevent hypoxemia in patients undergoing sedation for gastrointestinal (GI) endoscopy is of significant clinical value.

Current clinical research has primarily focused on hypoxemia occurring during the endoscopic procedure itself, whereas there is a paucity of high-quality evidence regarding the incidence and preventive measures of hypoxemia during the recovery phase. Specifically, the impact of body positioning on post-procedural hypoxemia remains largely unexplored. Emerging evidence suggests that the lateral decubitus position significantly reduces the incidence of hypoxemia during adult sedation. Anatomically, in the supine position, residual sedative effects combined with gravity cause the tongue and soft palate-structures lacking bony support-to collapse posteriorly, leading to upper airway obstruction. Conversely, the lateral position helps maintain a patent airway by preventing this collapse and optimizing the ventilation-perfusion (V/Q) matching, thereby stabilizing oxygenation.

Despite this theoretical basis, prospective studies investigating the effect of body positioning on recovery-phase hypoxemia in real-world settings are lacking. Therefore, this study hypothesizes that the lateral decubitus position reduces the incidence of recovery-phase hypoxemia compared to the supine position. Using prospective real-world data, we aim to validate this hypothesis and provide a simple, non-invasive, and cost-effective optimization strategy for clinical practice.

• Study Type: Interventional
• Enrollment (Estimated): 960
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Xiaoyong Wei, 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, Degree; 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

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Supine position group (Group S); The patient was turned from the predetermined left lateral position to the supine position without a head pillow (head-of-bed elevation at 0 degrees）	Procedure: Supine position group (Group S); Upon admission to the Post-Anesthesia Care Unit (PACU), an independent researcher (attending anesthesiologist) assessed the patient using the Ramsay Sedation Scale (1: anxious and agitated; 2: awake, calm, and cooperative; 3: drowsy but responsive to verbal commands; 4: asleep but responsive to tactile stimulation or pain; 5: asleep with a sluggish response to stimulation; 6: deep sleep with no response). Patients in the Supine Group (Group S) were turned from the predetermined lateral position to the supine position without a head pillow (head-of-bed elevation at 0 degrees). Standard monitoring was applied, and nasal cannula oxygen was administered at 2 L/min. If SpO₂ remained >95% for at least 5 minutes, oxygen was discontinued for observation. To ensure strict adherence to the protocol, an independent researcher continuously monitored and verified patient positioning (corrections were made only if the patient rolled unconsciously). Patients were evaluated using the Aldrete discharge
Experimental: Lateral decubitus position group (Group L); Upon arrival in the post-anesthesia care unit (PACU), the patient was kept in the left lateral decubitus position	Procedure: Lateral decubitus position group (Group L); Upon admission to the Post-Anesthesia Care Unit (PACU), an independent researcher (attending anesthesiologist) assessed the patient using the Ramsay Sedation Scale (1: anxious and agitated; 2: awake, calm, and cooperative; 3: drowsy but responsive to verbal commands; 4: asleep but responsive to tactile stimulation or pain; 5: asleep with a sluggish response to stimulation; 6: deep sleep with no response). Patients in the Lateral Group (Group L) were maintained in the predetermined left lateral position. Standard monitoring was applied, and nasal cannula oxygen was administered at 2 L/min. If SpO₂ remained >95% for at least 5 minutes, oxygen was discontinued for observation. To ensure strict adherence to the protocol, an independent researcher continuously monitored and verified patient positioning (corrections were made only if the patient rolled unconsciously). Patients were evaluated using the Aldrete discharge scoring system; discharge from the PACU occurred when a score of >9 was a

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
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.
Incidence of Severe Hypoxemia During Recovery	Proportion of participants experiencing severe hypoxemia, defined as pulse oxygen saturation (SpO₂) < 85% lasting >10 seconds during the post-procedure recovery period.	From PACU admission until discharge, assessed up to 30 minutes
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
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
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
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
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

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Prespecified Subgroup Analyses	Subgroup analyses will be conducted to explore heterogeneity of treatment effects on the primary outcome (incidence of recovery-phase hypoxemia) across baseline categories: Demographics: age (<65 vs ≥65 years), sex, body mass index (BMI) category; Clinical characteristics: ASA physical status (I-II vs III), smoking/alcohol history, Mallampati classification (I-II vs III-IV); Procedural factors: endoscopy type (gastroscopy vs colonoscopy vs combined), preprocedural hypoxemia (room-air SpO₂ ≤90%), history of pulmonary surgery, obstructive sleep apnea (OSA), respiratory comorbidities (asthma/COPD/chronic bronchitis/emphysema/bullae), and intraprocedural hypoxemia (SpO₂ ≤90% >10 s); Postprocedural sedation: Ramsay Sedation Score (2-6). Effect modification will be tested using interaction terms in regression models (or stratified analysis with Cochran-Mantel-Haenszel test).	From PACU admission until discharge, assessed up to 30 minutes

Collaborators and Investigators

• Sponsor: General Hospital of Ningxia Medical University
• Investigators: Study Chair: Xinli Ni, Doctoral, 86-951-674-3252

Study record dates

Study Major Dates

• Study Start (Estimated): April 23, 2026
• Primary Completion (Estimated): June 20, 2026
• Study Completion (Estimated): June 30, 2026

Study Registration Dates

• First Submitted: April 7, 2026
• First Submitted That Met QC Criteria: April 21, 2026
• First Posted (Actual): April 22, 2026

Study Record Updates

• Last Update Posted (Actual): April 22, 2026
• Last Update Submitted That Met QC Criteria: April 21, 2026
• Last Verified: April 1, 2026

More Information

Terms related to this study

• Other Study ID Numbers: dywe0001

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