Gas Composition in the Oropharynx During High-flow Oxygen Therapy Through Nasal Cannula in Healthy Volunteers

Overview

Observational, randomized studies and their meta-analyses have shown the high effectiveness of high-flow oxygen therapy through nasal cannulas, reaching 50-60% in acute hypoxemic respiratory failure. Some bench studies showed the advantages of high-flow oxygen therapy compared with standard oxygen therapy, consisting in reducing the anatomical dead space and maintaining a given inspiratory oxygen fraction in the hypopharynx of the mannequin, but the actual state of the gas composition of the hypopharynx was not studied. The study aim is measurement of the inspiratory (FiO2) and expiratory (FeO2) fractions of oxygen, as well as the inspiratory (FiСO2) and expiratory (FeСO2) fractions of carbon dioxide in the hypopharynx of healthy volunteers during high-flow oxygen therapy through nasal cannulas in different physiological conditions.

Randomized controlled trials showed reduction of tracheal intubation in high-flow oxygen therapy through nasal cannulas group in patients with acute respiratory failure as compared to standard oxygen therapy and noninvasive ventilation before Coronavirus disease-19 (COVID-19) pandemic. The World Health Organization (WHO) declared the outbreak a pandemic of COVID-19 on March 11th, 2020. Since then observational, randomized studies and their meta-analyses have shown the high effectiveness of high-flow oxygen therapy through nasal cannulas (HFNC), reaching 50-60% in acute hypoxemic respiratory failure. Bench studies showed the advantages of HFNC compared with standard oxygen therapy, consisting in reducing the anatomical dead space and maintaining a given inspiratory oxygen fraction in the hypopharynx of the mannequin, but the actual state of the gas composition of the hypopharynx during HFNC was not studied. The study aim is measurement of the inspiratory (FiO2) and expiratory (FeO2) fractions of oxygen, as well as the inspiratory (FiСO2) and expiratory (FeСO2) fractions of carbon dioxide in the hypopharynx of healthy volunteers during high-flow oxygen therapy through nasal cannulas in different physiological conditions.