Overview
Respiratory failure is characterized by low levels of oxygen and high levels of carbon dioxide in the blood which causes difficulty breathing. The management of patients with respiratory failure aims at improving oxygenation, and decreasing the effort required to breathe. Mechanical ventilation is a life-saving treatment, but may be associated with a high mortality rate, increased length of intensive care unit (ICU) stay and infection. Oxygenation techniques to avoid mechanical ventilation include standard oxygen therapy, continuous positive pressure (CPAP) and high-flow nasal cannula oxygen therapy (HFNC). CPAP consists of delivering oxygen through a mask. As compared to standard oxygen therapy, CPAP can promote lung recruitment leading to improved oxygenation and decreased work of breathing in patients with respiratory failure. Conversely, high-flow nasal cannula oxygen therapy (HFNC) delivers oxygen through nasal prongs. Oxygen is heated and humidified and can be delivered at different flows (from 10 - 60 L/min). As compared to standard oxygen therapy, HFNC can promote some lung recruitment leading to improved oxygenation, and decreased work of breathing. Therefore, the present study will have 2 phases:
Phase 1: we compared the physiological effects of different flows of HFNC to CPAP in healthy volunteers. The investigators hypothesize that the physiological effects of HFNC in the nasopharynx are comparable to that of CPAP at 4 cm H2O.
Phase 2: we will compare the physiological effects of different nasal interfaces of HFNC (Standard cannula vs. Asymmetrical cannula vs. Single-nostril adapted cannula) in healthy volunteers. The investigators hypothesize that the physiological effects of HFNC in the nasopharynx are comparable to that of CPAP at 4 cm H2O. We hypothesize that asymmetrical which is the cannula that has a higher cross-sectional area generates higher nasal pharyngeal pressure.
Eligibility
Inclusion Criteria:
- Healthy volunteers ≥ 18 y-o,
- No evidence of acute or chronic cardiopulmonary disease
Exclusion Criteria:
- Active epistaxis, sinus problem, nasal trauma, or deviated septum that would preclude the nasopharyngeal catheter insertion,
- Pregnancy, clinical evidence of respiratory illness, history of respiratory disease, body mass of over 50 kg/m2, ribcage malformation,
- Cardiac pace maker or implantable cardioverter-defibrillator according to EIT manufacturer,
- Allergy to topical lidocaine,
- Claustrophobia that would preclude the use of CPAP or HFNC.