Examining the Effects of Nasal High Flow Oxygen Therapy Compared to Non-invasive Ventilation in Health Volunteers
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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 compare 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.
End expiratory nasopharyngeal pressure (NP) [ Time Frame: 5 minutes ]
The primary endpoint is to compare the end expiratory nasopharyngeal pressure (NP) under 60 L/min of high flow nasal cannula (HFNC) to continuous positive airway pressure (CPAP 4 cmH2O). This will be assessed using a nasopharyngeal catheter.
Secondary Outcome Measures :
Change in physiologic variables of airway pressure at different flows of HFNC (20, 40, and 60 L/min) and CPAP (4 cmH20). [ Time Frame: 1 hour ]
One of the secondary endpoints is to compare variables of airway pressure at different flows of HFNC to CPAP. We will measure the end expiratory NP, mean NP, mean peak inspiratory pressure, mean peak expiratory pressure, delta inspiratory pressure and delta expiratory pressure.
Each of these variables will be measured for 1 minute using a nasopharyngeal catheter. Furthermore, at each flow of HFNC, we will ask the patient to breathe with their mouth open and mouth closed.
Change in end-expiratory lung impedance [ Time Frame: 1 hour ]
The other secondary endpoint is to compare the change in ventilation distribution and end-expiratory lung impedance at different flows of HFNC and CPAP. These variables will be measured using electrical impedance tomography (EIT) by placing a band around the chest of each participant.
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Layout table for eligibility information
Ages Eligible for Study:
18 Years and older (Adult, Older Adult)
Sexes Eligible for Study:
Accepts Healthy Volunteers:
Healthy volunteers responding to advertisement posted through the St. Michael's Hospital Communications board.
Healthy volunteers ≥ 18 y-o,
No evidence of acute or chronic cardiopulmonary disease
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.