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

Evaluation of Gas Composition in the Oropharynx During High-flow Oxygen Therapy Through Nasal Cannula in Healthy Volunteers: a Physiological Study

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.

Inclusion Criteria:

• Healthy Volunteers
• Age over 18 years
• Written informed consent.

Exclusion Criteria:

• Any primary or secondary lung diseases (COPD, bronchial asthma, interstitial lung diseases, metastatic lung disease, lung cancer)
• Any chronic diseases that can cause respiratory disorders (chronic heart failure, liver cirrhosis, systemic connective tissue diseases, cancer, neuromuscular diseases etc)
• Heart rhythm disturbances
• Body mass index more than 30 kg/m2
• Swallowing disorders
• History of epileptic syndrome
• Recent head surgery or anatomy that precludes the use of nasal cannulas
• Pregnancy and lactation period
• Inability to cooperate with staff.