The Effects of Flow Settings During High Flow Nasal Cannula for Healthy Volunteers and Adult Hypoxemia Patients

High flow nasal cannula (HFNC) delivers oxygen at a flow which exceeds the patient's
inspiratory flow demand in order to improve oxygenation. Numerous randomized control trials
and meta-analyses have shown that HFNC improves oxygenation and helps avoid intubation in
hypoxemic patients, as well as reduce work of breathing, improve ventilation, and decrease
hypercapnia in COPD patients. Flow settings play a critical role when using HFNC, as
increased flow can reduce inspiratory effort, improve ventilation, and dynamic lung
compliance. However, flow rates used in many studies vary widely, from 20-40 LPM in COPD
patients and 30-60 LPM in hypoxemic patients. The clinical effects of different HFNC flow
setting, specifically to match or over than a patients' own inspiratory flow, is still
unknown.

Inclusion Criteria:

- For hypoxemia study: Adult patients (Age > 18yrs and < 90yrs) who need nasal cannula
oxygen flow ≥ 5 L/min to maintain SpO2 at 90-97%.

- For healthy volunteer study: Adult subjects (Age > 18yrs and < 90yrs)

Exclusion Criteria (Common):

- Pregnant

- Unable to use resuscitation mask, such as facial trauma, claustrophobia

- Inability to verbally communicate;

- Inability to breathe via nose, such as nasosinusitis, stuffy nose or nasal
obstruction, etc.

Specific exclusion criteria for Hypoxemia study:

- Ordered SpO2 goal is above 97%

- FIO2 needs ≤ 0.4

- Using inhaled epoprostenol via HFNC

Specific exclusion criteria for Healthy volunteer study:

- Chronic pulmonary disease, such as asthma or COPD.