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NCT Number: NCT07380425

Deep Breathing With and Without Pressure Support and PEEP for Preoxygenation in Obese Patients

Obese patients are at increased risk of low oxygen levels during the induction of general anesthesia. Preoxygenation with a face mask before anesthesia is routinely used to increase oxygen reserves. This study compares three preoxygenation techniques: deep breathing alone, deep breathing with pressure-supported ventilation, and deep breathing with pressure-supported ventilation plus positive end-expiratory pressure (PEEP).

The main goal of the study is to determine how quickly each technique allows patients to reach an adequate level of oxygen in the lungs. In addition, the study evaluates whether these techniques cause gastric distension, which could increase the risk of regurgitation. Gastric ultrasound is used to assess stomach size before and after preoxygenation.

The results of this study will help identify the most effective and safest method of preoxygenation in obese patients undergoing elective surgery.

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Key information

Conditions

Obesity Body Weight Nutrition Disorders Nutritional and Metabolic Diseases Overnutrition Overweight Pathological Conditions, Signs and Symptoms Signs and Symptoms

Age range

18 year and older

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

Pamukkale University

Denizli, Turkey (Türkiye)

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Age ≥ 18 years
  • Obesity
  • Scheduled for elective surgery under general anesthesia
  • Able to cooperate with deep breathing during preoxygenation

Exclusion criteria

  • Hemodynamic instability
  • Poor cooperation
  • Preoperative oxygen therapy requirement
  • Conditions in which positive pressure ventilation may be harmful (e.g., increased intracranial or intraocular pressure)
  • Pregnancy
  • Emergency surgery
  • Beard (preventing adequate face mask seal)
  • Previous gastric surgery
  • Inability to visualize the gastric antrum by ultrasonography

Treatment and study plan

Deep Breathing Preoxygenation

Procedure

Preoxygenation performed with deep breathing using a ventilator delivering 100% oxygen at a flow rate of 12 L/min.

pressure support ventilation

Procedure

Application of pressure support ventilation with a pressure support level of 12 cmH₂O during preoxygenation.

positive end-expiratory pressure

Procedure

Application of positive end-expiratory pressure at a level of 6 cmH₂O during preoxygenation.

Primary outcomes

  1. Time to reach an end-tidal oxygen concentration (EtO₂) of 90%

    Time frame: Periprocedural (during the preoxygenation period, prior to induction of anesthesia)

    The time, in seconds, from the start of preoxygenation until the end-tidal oxygen concentration (EtO₂) reached 90%. End-tidal oxygen was measured at 30-second intervals using the anesthesia machine gas analyzer. Reaching EtO₂ 90% was defined as the endpoint of the preoxygenation period.

Secondary outcomes

  1. Heart rate

    Time frame: Periprocedural (baseline and pre-induction)

    Heart rate was measured at baseline (before the start of preoxygenation) and at the end of the preoxygenation period, defined as the time point when end-tidal oxygen concentration (EtO₂) reached 90%.

  2. Gastric antral cross-sectional area

    Time frame: Periprocedural (baseline and pre-induction)

    Gastric antral cross-sectional area measured by ultrasonography using a 2-5 MHz convex probe, calculated as (anteroposterior diameter × craniocaudal diameter × π)/4. Measurements were performed at baseline (before the start of preoxygenation) and at the completion of the preoxygenation period, defined as the time point when end-tidal oxygen concentration (EtO₂) reached 90%.

  3. Gastric distension score

    Time frame: Periprocedural (baseline and pre-induction)

    Epigastric gastric distension assessed using a 4-point ordinal scale (0 = none, 1 = mild, 2 = moderate, 3 = marked). The score was recorded at baseline (before the start of preoxygenation) and at the completion of the preoxygenation period, defined as the time point when end-tidal oxygen concentration (EtO₂) reached 90%.

  4. Reflux, belching, and discomfort

    Time frame: Periprocedural (baseline and pre-induction)

    Patient-reported occurrence of discomfort, symptomatic gastroesophageal reflux, or belching during the preoxygenation period. Events were assessed and recorded at the completion of the preoxygenation period, defined as the time point when end-tidal oxygen concentration (EtO₂) reached 90%.

  5. Systolic Blood Pressure

    Time frame: Periprocedural (baseline and pre-induction)

    Systolic blood pressure measured noninvasively at baseline (before the start of preoxygenation) and at the completion of the preoxygenation period, defined as the time point when end-tidal oxygen concentration (EtO₂) reached 90%.

  6. Diastolic Blood Pressure

    Time frame: Pre-induction (baseline and at completion of preoxygenation, defined by EtO₂ reaching 90%)

    Diastolic blood pressure measured noninvasively at baseline (before the start of preoxygenation) and at the completion of the preoxygenation period, defined as the time point when end-tidal oxygen concentration (EtO₂) reached 90%.

  7. Peripheral Oxygen Saturation (SpO₂)

    Time frame: Periprocedural (baseline and pre-induction)

    Peripheral oxygen saturation (SpO₂) measured at baseline (before the start of preoxygenation) and at the completion of the preoxygenation period, defined as the time point when end-tidal oxygen concentration (EtO₂) reached 90%.

Sponsors and collaborators

Lead sponsor

Pamukkale University

Other

Registry information

Official study title

Effects of Pressure Support and Positive End-Expiratory Pressure Added to Deep Breathing Preoxygenation on Gastric Distension in Obese Patients: A Randomized Controlled Trial

Important dates

Study start
2021
Primary completion
2022
Study completion
2022
First posted
Feb 2, 2026
Registry last updated
Feb 2, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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