Effect of Preoxygenation Position and Examination Position on Hypoxemia During Painless Gastrointestinal Endoscopy

Condition(s) studied

Investigational drug(s) / intervention(s)

Pre-oxygenation Position （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 ）: 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）: 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）: 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 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.

Eligibility

Primary outcome measure(s)

• Incidence of hypoxemia — During procedure
  Incidence of SpO₂ ≤ 90% for \>10 seconds during the examination.

Trial sites (1)

More General Hospital of Ningxia Medical University trials in China

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