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 Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
NONE
Enrollment
75
Preoxygenation performed with deep breathing using a ventilator delivering 100% oxygen at a flow rate of 12 L/min.
Application of pressure support ventilation with a pressure support level of 12 cmH₂O during preoxygenation.
Application of positive end-expiratory pressure at a level of 6 cmH₂O during preoxygenation.
Pamukkale University
Denizli, Turkey (Türkiye)
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.
Time frame: Periprocedural (during the preoxygenation period, prior to induction of anesthesia)
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%.
Time frame: 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%.
Time frame: 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%.
Time frame: 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%.
Time frame: 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%.
Time frame: 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%.
Time frame: 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%.
Time frame: Periprocedural (baseline and pre-induction)
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