THRIVE in Sedated Gastrointestinal Endoscopy

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.

• High-Flow Nasal Oxygen (THRIVE) (Device), also known as HFNO: Heated and humidified high-flow nasal oxygen was delivered via a THRIVE (Transnasal Humidified Rapid-Insufflation Ventilatory Exchange) system at a flow rate of 30 L/min with FiO₂ of 1.0, initiated 2 minutes prior to propofol induction and maintained continuously until the end of the procedure. The system generates nasopharyngeal positive pressure and reduces dead space, thereby supporting oxygenation and delaying desaturation during apneic episodes.
• Standard Nasal Cannula Oxygen (Device), also known as SNC: Supplemental oxygen was administered via a standard nasal cannula at a flow rate of 10 L/min, initiated 2 minutes prior to propofol induction and maintained continuously until the end of the procedure. This represents the standard of care for oxygen supplementation during procedural sedation for gastrointestinal endoscopy.

Primary outcomes

• Incidence of Hypoxemia During Procedural Sedation [From induction of sedation until end of the endoscopic procedure (estimated 10-30 minutes)]: Hypoxemia was defined as peripheral oxygen saturation (SpO₂) falling below 93% for a duration of ≥20 seconds, as measured by continuous pulse oximetry. The proportion of patients experiencing at least one hypoxemic episode was compared between the THRIVE and standard nasal cannula groups.

Secondary outcomes

• Need for Airway Intervention Due to Hypoxemia or Apnea [From induction of sedation until end of the endoscopic procedure (estimated 10-30 minutes)]: Proportion of patients requiring any of the following interventions during the procedure: jaw thrust or head extension maneuver, escalation of supplemental oxygen flow, or mask ventilation with 100% oxygen continued until SpO₂ ≥98%. Interventions were triggered by apnea (absence of respiratory activity or loss of ETCO₂ tracing for >20 seconds) or SpO₂ ≤93% for ≥20 seconds.
• Oxygen Reserve Index (ORi) Throughout the Procedure [Baseline, pre-induction, post-induction, intraoperative, and immediately after procedure completion]: ORi was continuously monitored using a non-invasive multiwavelength pulse co-oximetry sensor. Values were recorded at baseline, pre-induction, post-induction, during the procedure, and at procedure end. ORi reflects oxygen reserve in the moderate hyperoxic range (PaO₂ 100-200 mmHg) and was compared between groups at each time point.
• Peripheral Oxygen Saturation (SpO₂) Throughout the Procedure [Baseline, pre-induction, post-induction, intraoperative, and immediately after procedure completion]: SpO₂ was continuously monitored via pulse oximetry and recorded at baseline, pre-induction, post-induction, during the procedure, and at procedure end. Mean SpO₂ values and the number and duration of desaturation episodes were compared between the THRIVE and standard nasal cannula groups.
• Intraoperative Hemodynamic Stability [Baseline, pre-induction, post-induction, intraoperative, and immediately after procedure completion]: Mean arterial pressure (MAP) and heart rate (HR) were recorded at baseline, pre-induction, post-induction, during the procedure, and at procedure end. Hypotension was defined as MAP ≥25% below baseline; hypertension as ≥20% increase in systolic blood pressure from baseline; bradycardia as HR <60 bpm. The incidence of each event was compared between groups.

Sex: All, ages: 18 Years to any

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

• oznur demiroluk, MD, Principal investigator, fatih sultan mehmet research and training hospital