This prospective observational study aims to evaluate the effectiveness of Transnasal Humidified Rapid-Insufflation Ventilatory Exchange (THRIVE) compared to standard nasal cannula (SNC) oxygen supplementation in patients undergoing elective diagnostic gastroscopy under propofol sedation. The primary outcome is the incidence of hypoxemia (SpO₂ <93% for ≥20 seconds) during the procedure. Secondary outcomes include the need for airway intervention, Oxygen Reserve Index (ORi) values, peripheral oxygen saturation (SpO₂) levels, and hemodynamic parameters recorded throughout the procedure. Oxygen delivery method was selected by the attending anesthesia provider independent of the study team.

Procedural sedation for gastrointestinal endoscopy is associated with risks of respiratory depression, airway obstruction, and hypoxemia due to the pharmacological effects of sedative agents. Standard nasal cannula (SNC) oxygen supplementation, while widely used, is limited in its ability to guarantee adequate inspired oxygen concentrations, particularly during apneic episodes.

THRIVE (Transnasal Humidified Rapid-Insufflation Ventilatory Exchange) delivers heated and humidified oxygen at flow rates up to 70 L/min via a non-invasive nasal cannula. The high-flow system generates positive nasopharyngeal pressure, reduces anatomical dead space through a washout effect, increases end-expiratory lung volume, and extends safe apnea time by delaying arterial desaturation. These physiological mechanisms may offer significant advantages over standard low-flow oxygen delivery during sedated endoscopy.

In this single-center prospective observational study, adult patients (age ≥18, ASA I-III, BMI <35 kg/m²) undergoing elective diagnostic gastroscopy under propofol sedation were monitored with continuous SpO₂, ETCO₂, BIS, and non-invasive Oxygen Reserve Index (ORi) monitoring. Supplemental oxygen was provided either via THRIVE at 30 L/min or standard nasal cannula at 10 L/min, based on the attending anesthesiologist's preference. Preoxygenation was initiated 2 minutes before induction and continued until procedure completion. Sedation was maintained with propofol 1-1.5 mg/kg targeting BIS 60-80; fentanyl 0.5-1 mcg/kg was administered when required. Hemodynamic and respiratory parameters were recorded at baseline, pre-induction, post-induction, intraoperatively, and at procedure end. Airway interventions were standardized and applied when apnea lasted ≥20 seconds or SpO₂ dropped ≤93% for ≥20 seconds.

Inclusion Criteria:

• Age ≥18 years
• ASA physical status I-III
• Body mass index (BMI) <35 kg/m²
• Scheduled for elective diagnostic gastroscopy under propofol sedation
• Baseline SpO₂ >93% on room air prior to the procedure
• Hemoglobin level ≥10.0 g/dL prior to the procedure
• Willing and able to provide written informed consent

Exclusion Criteria:

• Severe chronic pulmonary disease (e.g., COPD, interstitial lung disease)
• Severe chronic cardiac disease
• BMI ≥35 kg/m²
• Pregnancy
• History of facial or oropharyngeal surgery
• Baseline SpO₂ ≤93% on room air prior to the procedure
• Hemoglobinopathy
• Hemoglobin level <10.0 g/dL prior to the procedure

Adult patients aged 18 years and older with ASA physical status I-III and BMI <35 kg/m², scheduled for elective diagnostic gastroscopy under propofol sedation at a single tertiary care center. Patients with severe cardiopulmonary disease, pregnancy, prior facial or oropharyngeal surgery, baseline hypoxemia, hemoglobinopathy, or significant anemia were excluded. Supplemental oxygen delivery method (THRIVE vs. standard nasal cannula) was determined by the anesthesia provider independently of the study team.

No formal data sharing plan has been established at this time. Individual participant data sharing will be considered upon reasonable request, subject to ethical approval and institutional regulations.