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Completed

NCT Number: NCT07019701

Gas Composition in the Hypopharynx During High-flow or Standard Oxygen Therapy Through Face Mask in Healthy Volunteers

The COVID-19 pandemic has become a huge global problem, affecting all spheres of human life, resulting in enormous social, economic consequences and human tragedies. With very decent results of treatment of patients of average severity in the conditions of bed units, the results of treatment of the most severe category - patients of intensive care units who required tracheal intubation remain extremely unsatisfactory. According to different data, mortality in this category of patients reaches 80-90%. However, observational, randomized studies and their meta-analyses have shown high efficiency of high-flow oxygen therapy through nasal cannulas, reaching 50-60%. Some pilot bench studies (on manikins) have shown the advantages of high-flow oxygen therapy over standard oxygen therapy in reducing anatomical dead space and preserving a given inspiratory fraction of oxygen in the laryngeal pharynx of the manikin, but the actual state of the laryngeal pharyngeal gas composition was not studied. Some patients breathe through open mouth that decreases the efficacy oh high flow oxygen through nasal cannula. The aim of the study is to measure the inspiratory (FiO2) and expiratory (FeO2) oxygen fractions and the inspiratory and expiratory carbon dioxide fractions (FiCO2 and FeCO2, respectively) in the hypopharynx of healthy volunteers during high-flow oxygen therapy through nasal cannula and face mask, and during standard oxygen therapy through non-rebreather face mask under different physiological conditions.

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Key information

Conditions

Healthy Volunteers

Age range

18 year–50 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

Sechenov University Clinic#4

Moscow, 119991, Russia

About this study

Randomized controlled trials showed reduction of tracheal intubation in high- flow oxygen therapy through nasal cannula 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. Some patients breathe through open mouth that decreases the efficacy oh high flow oxygen through nasal cannula.

The aim of the study is to measure the inspiratory (FiO2) and expiratory (FeO2) oxygen fractions and the inspiratory and expiratory carbon dioxide fractions (FiCO2 and FeCO2, respectively) in the hypopharynx of healthy volunteers during high-flow oxygen therapy through nasal cannula and face mask, and during standard oxygen therapy through non-rebreather face mask under different physiological conditions.

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Healthy Volunteers
  • Age 18-50 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.

Treatment and study plan

High flow oxygen through nasal cannula and face mask and standard oxygen therapy through non-rebreather face mask, and measurement of oxygen and carbon dioxide fraction in the hypopharynx

Device

High flow oxygen through nasal cannula and face mask, and standard oxygen therapy through non-rebreather face mask, and measurement of oxygen and carbon dioxide fraction in the hypopharynx of healthy volunteers in different physiological conditions

Primary outcomes

  1. Inspiratory oxygen fraction (FiO2) in the hypopharynx

    Time frame: 5 minutes after the start of each combination of breathing pattern, device type, fraction of inspired oxygen and preset flow

    Inspiratory oxygen fraction (FiO2) in the hypopharynx during high flow oxygen therapy through nasal cannula and face mask, and standard oxygen therapy through non-rebreather face mask different physiological conditions

  2. Expiratory oxygen fraction (FeO2) in the hypopharynx

    Time frame: 5 minutes after the start of each combination of breathing pattern, device type, fraction of inspired oxygen and preset flow

    Expiratory oxygen fraction (FeO2) in the hypopharynx during high flow oxygen therapy through nasal cannula and face mask, and standard oxygen therapy through non-rebreather face mask different physiological conditions

  3. Expiratory fraction of carbon dioxide (FeCO2) in the hypopharynx

    Time frame: 5 minutes after the start of each combination of breathing pattern, device type, fraction of inspired oxygen and preset flow

    Expiratory fraction of carbon dioxide (FeCO2) in the hypopharynx during high flow oxygen therapy through nasal cannula and face mask, and standard oxygen therapy through non-rebreather face mask different physiological conditions

Secondary outcomes

  1. Respiratory rate (RR)

    Time frame: 5 minutes after the start of each combination of breathing pattern, device type, fraction of inspired oxygen and preset flow

    Respiratory rate (RR)

  2. Peripheral oxygen saturation (SpO2)

    Time frame: 5 minutes after the start of each combination of breathing pattern, device type, fraction of inspired oxygen and preset flow

    Peripheral oxygen saturation (SpO2) during different physiological conditions

  3. The ratio of oxygen saturation by pulse oximetry/inspiratory oxygen fraction to respiratory rate (ROX-index)

    Time frame: 5 minutes after the start of each combination of breathing pattern, device type, fraction of inspired oxygen and preset flow

    The ratio of oxygen saturation by pulse oximetry/inspiratory oxygen fraction to respiratory rate (ROX-index) during different physiological conditions

  4. Comfort

    Time frame: 5 minutes after the start of each combination of breathing pattern, device type, fraction of inspired oxygen and preset flow

    Visual-analog scale (VAS) for comfort evaluation (from 1 to 10, 1-full comfort, 10-full comfort)

Sponsors and collaborators

Lead sponsor

I.M. Sechenov First Moscow State Medical University

Other

Registry information

Official study title

Gas Composition in the Hypopharynx During High-flow Oxygen Therapy Through Nasal Cannula or Face Mask, or During Standard Oxygen Therapy Through a Non-Rebreather Face Mask in Healthy Volunteers

Acronym: O2-OXIMETRY

Important dates

Study start
2025
Primary completion
2025
Study completion
2025
First posted
Jun 13, 2025
Registry last updated
Mar 25, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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