Study will be conducted in the intensive care units (ICU) of Ain Shams University Hospitals, Cairo, Egypt. Consented and enrolled seventy patients will be randomly assigned to one of the following two groups:
* Conventional nasal oxygen therapy (COT) group (35 patients): Who will receive 5 L/min oxygen flow through standard nasal cannula (gives FiO2 of about 0.4). The allocated flow rates will be maintained throughout the procedure unless intervention will be required at the discretion of the anesthesiologist in charge of the case.
* High-flow nasal cannula (HFNC) group (35 patients): Who will receive 30 L/min oxygen flow through Vapotherm Precision Flow HFNC. The fraction of inspired Oxygen (FiO2) will be adjusted at 0.4,temperature at 37◦C with 100% humidity
* Upper Gastrointestinal (UGI) Endoscopic and anesthetic care as following:
* Pre-procedural full medical and anesthetic history, clinical examination and revision of routine investigations and radiological images will be done.
* Standard monitoring via GE monitor will be connected to the patient as electrocardiogram (ECG) for heart rate (beats/min), pulse oximetry for (SpO2 as a percentage) and non invasive blood pressure (NIBP) (mmHg).
* The intravenous access (IV) will be assessed and flow will be assured
* After positioning the patient in the left lateral position, he will receive either HFNC or COT.
* All UGI endoscopic procedures will be performed by an accredited gastroenterologist. Anesthetic care will be provided by an accredited specialist anesthesiologist. After confirming the readiness of the endoscopist, all patients will undergo deep sedation under monitored anesthetic care with the use of initial slow intravenous (IV) propofol 0.5-1mg/kg over 3-5 minutes which will be titrated to the desired clinical response.Intermittent boluses of 10-20 mg will be used as maintenance and will also be titrated to the desired sedation level. Both the endoscopist and anesthesiologist will be instructed to provide the usual care except for the participant's assigned oxygen delivery device and rate.
* Interventions to change the oxygen delivery rate, Fio2 or even intubation with invasive mechanical ventilation in response to hypoxia will be at the discretion of the anesthesiologist in charge.
* UGI diagnostic and therapeutic endoscopy will be performed by PentaxR Medical 90k series gastroscopy. Therapeutic gastroscopy will include variceal band ligation, endoscopic hemostasis as injection of bleeding peptic ulcers with adrenaline or bleeders control via either argon plasma coagulation (APC) or heater probe coagulation.
* Patients will continue their monitored care in the medical ICU till the control of the causes of their ICU admission or their end.
* Demographics and medical conditions will be collected from the medical records and anesthesiologist assessments. Oxygenation, anesthetic and procedure-related (intraprocedural and shortly post- procedural) data will be collected also. The collected data results will be revised, electronically recorded in datasheet, coded, tabulated, analyzed, and processed using the proper computerized statistical package program. Suitable statistical analysis will be done according to the type of data obtained for each parameter with comparison between both groups to identify any significant differences between them
