High-flow Nasal Oxygen Therapy in Obese Patients Undergoing Sedative Gastroscopy

Gastroscopy is a common method for screening and diagnosing digestive diseases, with approximately 23 million cases performed in China annually. However, this invasive procedure can cause patients to experience pain, nausea, vomiting, and coughing. With the advancement of comfortable medical technology, more patients are opting for painless gastroscopy, which offers higher comfort and satisfaction levels for patients and facilitates the operation for endoscopists.

During sedative gastroscopy, nasal cannula oxygen therapy is commonly used to maintain oxygen levels, with oxygen flow rates typically ranging from 2-6L/min. The most common complication during the procedure is hypoxia. For obese patients, the risk of hypoxemia is increased due to fat accumulation in the head and neck, increased soft tissue in the oropharynx, decreased lung compliance and volumes, and potential obstructive sleep apnea. Therefore, appropriate oxygen therapy is crucial in preventing complications in obese patients during gastroscopy.

High-flow nasal cannula oxygen therapy (HFNC) is a new ventilation method that provides patients with high-flow oxygen (20-70L/min) through a special nasal cannula, with adjustable oxygen concentration (21%-100%) and warming and humidifying functionalities. HFNC can alleviate mucosal ciliary pressure, maintain airway patency and moisture, reduce the risk of nasal bleeding, and generate positive airway pressure, aiding in alveolar recruitment and preventing atelectasis.

Studies have shown that HFNC can reduce the occurrence of hypoxia during painless gastroscopy compared to standard oxygen therapy. The positive airway pressure provided by HFNC is crucial in reducing upper airway obstruction and improving ventilation. The optimal flow rate for HFNC in obese patients undergoing gastroscopy remains unclear, but starting at 30L/min has shown benefits in reducing the risk of hypoxemia without significant discomfort.

Therefore, the investigators propose to investigate the effects of HFNC at flow rates of 30L/min, 50L/min, and 70L/min during painless gastroscopy in obese patients to determine the optimal flow rate that minimizes the risk of hypoxemia without causing discomfort.

Inclusion criteria

• Patients undergoing sedative gastroscopy
• Aged over 18.
• ASA classification I-III
• Interincisal distance >6.5cm, no micrognathia, limited mouth opening and limited cervical spine movement
• Compliance with ethics, patient willing to participate in the trial, signed informed consent form

Exclusion criteria

• Contraindications for endoscopic procedures or patients refusing sedation/anesthesia.
• Patients with allergies to propofol, eggs, soybeans, or milk.
• Patients with gastrointestinal obstruction and gastric emptying disorders.
• Patients with acute pharyngitis, tonsillitis, and upper respiratory tract infections.

5: Patients with acute exacerbations of respiratory diseases such as asthma, bronchitis, and COPD. 6. Patients with acute arrhythmias and severe heart disease (congenital, valvular disease). 7. Patients requiring replacement therapy for severe liver or kidney dysfunction.

• Patients with severe mental illnesses requiring medication to control symptoms.

• Patients with moderate to severe anemia, coagulation disorders, and hematological diseases. 10. Patients with severe nasal congestion caused by nasal cavity lesions. 11. Pregnant and lactating patients.