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

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

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.

Study Overview

• Status: Completed
• Conditions: Obesity
• Intervention / Treatment: Procedure: Positive End-Expiratory Pressure; Procedure: Deep Breathing Preoxygenation; Procedure: Pressure Support Ventilation

• Study Type: Interventional
• Enrollment (Actual): 75
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Turkey (Türkiye)
  • Denizli, Turkey (Türkiye)
    • Pamukkale University

Participation Criteria

Eligibility Criteria

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

Description

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

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: None (Open Label)

Number of Arms

3

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: DB (Deep Breathing); Deep breathing preoxygenation with 100% oxygen at 12 L/min using.	Procedure: Positive End-Expiratory Pressure; Application of positive end-expiratory pressure at a level of 6 cmH₂O during preoxygenation.
Experimental: DB+PSV; Preoxygenation with deep breathing supported by pressure-supported ventilation (PSV-Pro) with 12 cmH₂O pressure support and 100% oxygen at 12 L/min until EtO₂ reached 90%.	Procedure: Deep Breathing Preoxygenation; Preoxygenation performed with deep breathing using a ventilator delivering 100% oxygen at a flow rate of 12 L/min.
Experimental: DB+PSV+PEEP; Deep breathing preoxygenation supported by PSV-Pro (pressure support 12 cmH₂O) with the addition of PEEP 6 cmH₂O; 100% oxygen at 12 L/min. This arm differs from Arm 2 by the application of PEEP.	Procedure: Pressure Support Ventilation; Application of pressure support ventilation with a pressure support level of 12 cmH₂O during preoxygenation.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Time to reach an end-tidal oxygen concentration (EtO₂) of 90%	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.	Periprocedural (during the preoxygenation period, prior to induction of anesthesia)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Heart rate	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%.	Periprocedural (baseline and pre-induction)
Gastric antral cross-sectional area	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%.	Periprocedural (baseline and pre-induction)
Gastric distension score	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%.	Periprocedural (baseline and pre-induction)
Reflux, belching, and discomfort	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%.	Periprocedural (baseline and pre-induction)
Systolic Blood Pressure	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%.	Periprocedural (baseline and pre-induction)
Diastolic Blood Pressure	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%.	Pre-induction (baseline and at completion of preoxygenation, defined by EtO₂ reaching 90%)
Peripheral Oxygen Saturation (SpO₂)	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%.	Periprocedural (baseline and pre-induction)

Collaborators and Investigators

• Sponsor: Pamukkale University

Publications and helpful links

General Publications

• Nimmagadda U, Chiravuri SD, Salem MR, Joseph NJ, Wafai Y, Crystal GJ, El-Orbany MI. Preoxygenation with tidal volume and deep breathing techniques: the impact of duration of breathing and fresh gas flow. Anesth Analg. 2001 May;92(5):1337-41. doi: 10.1097/00000539-200105000-00049.
• Abou-Arab O, Guinot PG, Dimov E, Diouf M, de Broca B, Biet A, Zaatar R, Bernard E, Dupont H, Lorne E. Low-positive pressure ventilation improves non-hypoxaemic apnoea tolerance during ear, nose and throat pan-endoscopy: A randomised controlled trial. Eur J Anaesthesiol. 2016 Apr;33(4):269-74. doi: 10.1097/EJA.0000000000000394.
• Taxak S, Gupta M, Bala R, Govil V, Lallar A. A prospective randomized study to evaluate the efficacy of pressure support ventilation with and without positive end expiratory pressure for preoxygenation in adult patients. Med Gas Res. 2023 Oct-Dec;13(4):187-191. doi: 10.4103/2045-9912.372665.
• Hanouz JL, Lammens S, Tasle M, Lesage A, Gerard JL, Plaud B. Preoxygenation by spontaneous breathing or noninvasive positive pressure ventilation with and without positive end-expiratory pressure: A randomised controlled trial. Eur J Anaesthesiol. 2015 Dec;32(12):881-7. doi: 10.1097/EJA.0000000000000297.
• Delay JM, Sebbane M, Jung B, Nocca D, Verzilli D, Pouzeratte Y, Kamel ME, Fabre JM, Eledjam JJ, Jaber S. The effectiveness of noninvasive positive pressure ventilation to enhance preoxygenation in morbidly obese patients: a randomized controlled study. Anesth Analg. 2008 Nov;107(5):1707-13. doi: 10.1213/ane.0b013e318183909b.

Study record dates

Study Major Dates

• Study Start (Actual): December 1, 2021
• Primary Completion (Actual): July 25, 2022
• Study Completion (Actual): July 25, 2022

Study Registration Dates

• First Submitted: January 11, 2026
• First Submitted That Met QC Criteria: January 28, 2026
• First Posted (Actual): February 2, 2026

Study Record Updates

• Last Update Posted (Actual): February 2, 2026
• Last Update Submitted That Met QC Criteria: January 28, 2026
• Last Verified: January 1, 2026

More Information

Terms related to this study

• Keywords: obesity; Preoxygenation; Pressure Support Ventilation; Positive End-Expiratory Pressure; Gastric Antrum Area
• Additional Relevant MeSH Terms: Nutrition Disorders; Overnutrition; Body Weight; Overweight; Pathological Conditions, Signs and Symptoms; Nutritional and Metabolic Diseases; Signs and Symptoms; Obesity; Therapeutics; Airway Management; Respiratory Therapy; Respiration, Artificial; Positive-Pressure Respiration
• Other Study ID Numbers: PamukkaleUCTanriverdi-002

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