Comparison of Preoxygenation Techniques in Healthy Volunteers With Monitoring of End-tidal Oxygen Fraction (FeO₂) and Oxygen Reserve Index (ORI)

Comparison of Preoxygenation Techniques in Healthy Volunteers With Monitoring of End-tidal Oxygen Fraction (FeO₂) and Oxygen Reserve Index (ORI).

The objective of this physiological study is to compare two preoxygenation techniques (non-invasive ventilation combined with high-flow nasal oxygen versus non-invasive ventilation alone) by monitoring end-tidal oxygen fraction (FeO₂) and the Oxygen Reserve Index (ORI) during 3 minutes of preoxygenation in healthy volunteers.

An intubation procedure is performed in several successive phases:

1. Preoxygenation phase: This phase consists of administering 100% oxygen for 3 to 5 minutes in order to increase oxygen reserves.
2. Alveolar hypoventilation phase: This phase begins with the administration of anesthetic agents, leading to a reduction in spontaneous ventilation.
3. Apnea phase: During this phase, laryngoscopy is performed and the endotracheal tube is inserted into the trachea.
4. Initiation of invasive mechanical ventilation: Once intubation is successful, the patient is placed on assisted mechanical ventilation.

Several devices can be used to perform preoxygenation:

• Bag-valve mask (BVM)
• High-flow nasal cannula therapy (HFNC)
• Non-invasive ventilation (NIV):

Current recommendations from critical care societies suggest the use of:

• BVM or HFNC for non-hypoxemic patients
• NIV for hypoxemic patients A single-center randomized controlled study (OPTINIV) demonstrated the benefit of combining NIV and HFNC for preoxygenation. However, placing an NIV mask over HFNC nasal cannulae may result in mask leaks, leading to ambient air entrainment, as well as a potential risk of excessive airway pressure related to HFNC. In this study, HFNC cannulae in the control group were left in place but inactive. Consequently, it remains difficult to determine whether the observed efficacy of the NIV + HFNC combination was related to leak compensation by HFNC during preoxygenation, or to apneic oxygenation provided by HFNC between laryngoscopy and successful intubation.

Inclusion Criteria:

• Male or female
• Healthy volunteer who has provided written informed consent
• Age > 18 years

Exclusion Criteria:

• Long-term oxygen therapy
• Cardiac or pulmonary disease (including asthma)
• Presence of Raynaud's syndrome
• Claustrophobia
• Body mass index (BMI) ≥ 30 kg/m²
• Presence of nail polish preventing accurate SpO₂ and ORI measurement
• Under legal protection
• Incarcerated individuals
• Persons deprived of liberty
• Not affiliated to French social security
• Pregnant or breastfeeding women
• Individuals currently participating in a drug study and still within the exclusion period