The Comparison of Low- and High-flow Nasal Oxygenation to the Blood Oxygen Saturation During Analgo-sedation in ASA Risk Class I, II and III Normal Weight Patients: Randomized Controlled Trial

Analgo-sedation is standard procedure in anesthesiology practice and is often given for diagnostic and procedural intervention in the setting of daily hospital. Institution of sedation and maintaining spontaneous breathing are main characteristics of analgo-sedation. Preservation of adequate patient oxygenation is set up by continuous administration of sedative anesthetic infusion which contributes to hemodynamic stability and by administration of oxygen. Patient oxygenation is implemented prior to analgo-sedation (preoxygenation), during analgo-sedation (periprocedural oxygenation) and during awakening from analgo-sedation (postprocedural oxygenation) usually via nasal cannula with application of low-flow (2-6 L/min) up to 40% of inspired fraction of oxygen (LFNO: low-flow nasal oxygenation, FiO2: inspiratory fraction of oxygen). Despite oxygenation administered, intravenously applied analgo-sedation yields to risk of transitory apnea accompanied by hypoxemia, hypoxia, hypercapnia and hemodynamic insufficiency. Anesthesia risk is classified as ASA classification by American Society of Anesthesiologist Physical Status Classification System: ASA I includes healthy patients without systemic disease, ASA II patients who have mild systemic disease without functional organ limitations and ASA III patients with one or more organ function insufficiency.

High-flow heated and humidified oxygenation (HFNO) delivered via soft, specially designed, nasal cannula is successfully used for preoxygenation of patient with predicted difficulty in ensuring airway patency. Unlike LFNO, HFNO is characterized by high flow of heated and humidified oxygen-air mixture (20-70 L/min) up to 100% FiO2. HFNO prolongs adequate oxygenation time in patients during retrograde endoscopic cholangiopancreatography. Also, HFNO could be alternative for noninvasive ventilation of patients with acute hypoxemic respiratory failure. According to previously mentioned statements, LFNO has significant limitations. Main characteristic of HFNO as innovative technique is supporting patients' spontaneous inspiration effort through high-flow of heated and humidified oxygen-air mixture. Higher inspiratory fraction of oxygen, positive end-expiratory pressure, decreasing of pharyngeal airway dead space and decreasing of airway resistance lead to improved maintaining of oxygenation combined with better patients' tolerance.

AIM of this study is to compare effect of HFNO and LFNO during standardized procedure of intravenous analgo-sedation on periprocedural oxygenation maintenance in normal weight patients of ASA I, II and III status.

Investigators hypothesized that application of HFNO compared to LFNO, in patients with preserved spontaneous breathing during procedural analgo-sedation, contributes to maintaining adequate oxygenation, consequently adding to greater peri-procedural circulatory and respiratory stability of these patients. Investigators expect that HFNO will ensure reduced bradypnoea intervals (frequency of breathing, FoB 1/min), longer maintenance of adequate oxygenation, shorter intervals of desaturation (SpO2 ≤ 92%), reducing hypercapnia (PaCO2 ≥ 6 kPa) and less airway - opening maneuvers performed by attending anesthesiologist (Aom). These will prevent partial respiratory insufficiency detected by low SpO2 or low PaO2 ≤ 11kPa accompanied by normal or low PaCO2 ≤ 6 kPa, and global respiratory insufficiency detected by decreased SpO2 ≤ 92% and PaO2 ≤ 11kPa with increased PaCO2 ≥ 6 kPa.

Investigators plan to conduct prospective, parallel group, randomized controlled clinical trial. Trial will be managed according to principles of Declaration of Helsinki for scientific clinical research and will be planned and guided according to CONSORT guidelines (Consolidated Standards of Reporting Trials). The trial has been approved by hospital's Ethic Committee.