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High‑Flow Oxygen to Reduce Hypoxemia in High‑Risk Adults Undergoing Sedated Gastroscopy, Colonoscopy or Endoscopic Ultrasound

Registered drugNo placebo
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What is this trial about?

A plain-language summary of the goals, design and what participants do

The study focuses on patients who may experience hypoxemia—a condition where blood oxygen levels become too low—while undergoing digestive endoscopy procedures such as gastroscopy, colonoscopy, or oral endoscopic ultrasound performed under deep sedation. The intervention being tested is the delivery of high-flow oxygen therapy using a medical oxygen gas, which provides a higher rate of oxygen to help keep blood oxygen levels stable during the procedure.

The purpose of the study is to determine whether this oxygen approach reduces the number of low‑oxygen events and related complications during sedated endoscopic examinations. Participants will be randomly assigned to receive either the high‑flow oxygen or the standard oxygen method, and they will be observed throughout the endoscopic procedure and the short recovery period. Researchers will monitor for signs such as abnormal breathing patterns measured by capnography (a test that tracks carbon dioxide in the breath), as well as heart‑related issues including bradycardia (slow heart rate), hypotension (low blood pressure), arrhythmias (irregular heartbeats), pulmonary aspiration (inhaling fluids into the lungs), and cardiorespiratory arrest (stopping of heart and breathing).

Data will be collected during the endoscopic session and shortly afterward to evaluate the safety and effectiveness of the high‑flow oxygen approach compared with the standard method, with the goal of improving patient safety during these procedures.

The research process

The trial runs in 7 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Enrollment and consent

    After signing the consent form, you receive a study identification number.

    Baseline information such as age, medical history, and current medications is recorded.

  2. Step 2

    Randomization

    You are assigned by the study system to receive either the high-flow oxygen treatment or the standard care used in the trial.

  3. Step 3

    Pre‑procedure preparation

    You arrive at the endoscopy unit on the scheduled day.

    Fasting instructions are confirmed and vital signs (blood pressure, heart rate, oxygen saturation) are measured.

  4. Step 4

    Administration of high‑flow <b>oxygen</b>

    A nasal cannula is placed and the device is set to deliver a flow of 70 lm lumen.

    The oxygen is given continuously by inhalation beginning before the start of sedation and maintained for the entire endoscopic examination.

  5. Step 5

    Digestive endoscopy under deep sedation

    The endoscopic procedure (gastroscopy, colonoscopy, or oral endoscopic ultrasound) is performed while you are under deep sedation.

    Monitoring devices record oxygen levels, breathing pattern, heart rate, and blood pressure throughout the procedure.

  6. Step 6

    Post‑procedure observation

    After the endoscopy, the high‑flow oxygen continues for a short period until your oxygen saturation is stable.

    Vital signs are checked regularly until you meet the criteria for safe discharge.

  7. Step 7

    Discharge

    Once stable vital signs and adequate oxygen levels are confirmed, you are allowed to leave the facility with written instructions for home care.

Who can join the trial?

8 criteria

  • Be at least 18 years old.
  • Provide a signed informed consent (agree in writing to take part after understanding the study).
  • Have obesity, meaning a body‑mass index (BMI) of 30 kg/m² or higher (BMI is a number that compares weight to height).
  • Be classified as ASA physical status III (a medical rating that indicates you have a serious but not life‑threatening health problem).
  • Have a stable pulmonary (lung) disease, with no hospital admission for lung issues in the past six months.
  • Have a stable heart failure, with no hospital admission for heart problems in the past six months.
  • Have diagnosed or suspected obstructive sleep apnea (OSA), shown by a STOP‑Bang score of 3 or more (a questionnaire that helps identify sleep‑breathing problems).
  • Have a history of complications related to sedation during a previous endoscopic procedure (such as gastroscopy, colonoscopy, or oral ultrasound performed while you were deeply sedated).

Who cannot join the trial?

8 criteria

  • ASA physical status IV: This means the person has severe overall health problems that make surgery or procedures riskier.
  • Having a recent heart failure that is worsening or unstable (hospital stay for heart problems in the past 6 months) at the time of the endoscopy.
  • Having a recent respiratory disease that is worsening or unstable (hospital stay for lung problems in the past 6 months) at the time of the endoscopy.
  • Being pregnant.
  • Using long‑term home oxygen therapy, meaning they need continuous oxygen at home.
  • Having an orotracheal tube placed in the airway (a tube through the mouth into the windpipe).
  • Having a tracheostomy (a tube placed directly in the neck into the windpipe).
  • Having a known allergy to propofol or a medical reason that makes using this medication unsafe.
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Investigated drugs

Medical Oxygen (high‑flow) is a medicinal gas given to patients through a breathing mask or nasal cannula. In this study it is used during digestive endoscopy procedures while the patient is under deep sedation. The oxygen is supplied at a high flow rate to keep the blood oxygen level stable and to prevent episodes of low oxygen (hypoxemia). By providing a steady and abundant supply of oxygen, the therapy aims to improve safety and reduce breathing problems during the procedure.

What is already known about the treatment

Medical Liquid Oxygen (Air Liquide) - It is supplied as a cryogenic medicinal gas stored in fixed containers and is given to patients by inhalation, usually through a high‑flow device such as a nasal cannula during the procedure. Medical oxygen is an approved and widely used therapy that appears in many clinical publications. It is used to prevent or treat low blood‑oxygen levels (hypoxemia) that can happen during deep‑sedated endoscopic examinations. The gas works by increasing the amount of oxygen that enters the bloodstream and is classified as a respiratory medical gas.

Investigated diseases

Hypoxemia - Hypoxemia is a condition where the level of oxygen in the blood falls below normal. It can develop during procedures that require deep sedation because breathing may become shallow. As oxygen levels drop, a person may feel short of breath or become dizzy. If the low oxygen persists, the heart may beat faster to compensate. The condition can worsen gradually if the underlying cause is not addressed, leading to more noticeable symptoms.
Trial detailsLast updated 2 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2026-525766-21-01Protocol codeICSCYL-2025-097-OXYEstimated enrolment326 patientsSponsorHospital Universitario Rio Hortega

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