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(U IZRADI) Influence of high-flow- compared to low-flow-nasal oxygenation on maintenance of spontaneous respiration during intravenous analgo-sedation

Analgo-sedation is standard of anesthesiologic praxis and is often given for diagnostic and procedural intervention in the setting of daily hospital.1, 2 Institution of sedation and maintaining spontaneous breathing are main characteristics of these anesthetic procedures. Preservation of adequate patient oxygenation is set up by continuous administration of sedative anesthetic infusion which contributes to hemodynamic stability and, of course, by administration of oxygenation. 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 respiratory and hemodynamic insufficiency.3 Before-mentioned complications can be coupled with certain mortality rate, especially at higher-risk ASA III class patients (American Society of Anesthesiologist – Physical status system classification 2015, ASA III - patient with one of organ functions impaired, with substantive functional limitations combined with one or more moderate to severe diseases.).1, 4 It is known that obese patients during analgo- sedation are prone to intervals of bradypnoea and hypoventilation. High flow heated and humidified oxygenation (HFNO) delivered via soft, specially designed, nasal cannula is successfully, with proved clinical effect, used for preoxygenation at patient with predicted difficult ensurence of airway (THRIVE, Transnasal Humidified Rapid- Insufflation ventilatory exchange). It also successfully used as additional oxygenation to maintained spontaneous patients breathing: during procedures where such breathing is necessary, for supported breathing in the process of weaning form mechanical ventilation or after awakening from general anesthesia (POINT, Peri-Operative Insufflatory Nasal Therapy).6 Unlike previously described LFNO, using of HFNO is characterized by high flow of heated and humidified oxygen-air mixture (20-70 L/min) up to 100% FiO2.5 It is already known that HFNO prolongs adequate oxygenation period in patients during retrograde endoscopic cholangiopancreatography.7 Also, HFNO could be alternative for noninvasive ventilation of patients with acute hypoxemic respiratory failure who can not tolerate noninvasive ventilation (NIV- noninvasive ventilation).8 It was found that application of HFNO is more successful than LFNO and NIV in decreasing necessity for endotracheal intubation in patients with acute respiratory failure.9 According to previously mentioned statements, LFNO has significant limitations. Main characteristic of HFNO as innovative technique is supporting patients’ spontaneous inspiratory 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 better maintaining of oxygenation combined with better patients’ tolerance.5 So far, effect of HFNO as noninvasive breathing support on spontaneous breathing and maintenance of adequate oxygenation in analgo-sedated, adipose patients of ASA III class has not been studied. AIM of this study is to compare effect of HFNO and LFNO during standardized procedure of intravenous analgo-sedation on periprocedural oxygenation maintenance in adipose patients of low- (ASA I or II status) and high - anesthetic risk (ASA III status). (ASA ; American Society of Anesthesiology, I=without organ functions impaired, II = mild diseases only without substantive functional limitations, III = one or more organ function insufficiency).

analgo-sedation, oxygenation

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