The Effects of Flow Settings During High Flow Nasal Cannula for 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

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

Exclusion criteria

(Common): - Unable to use resuscitation mask, such as facial trauma, claustrophobia

• Inability to verbally communicate;
• Pregnant
• Inability to breathe via nose, such as nasosinusitis, stuffy nose or nasal obstruction, etc.
• Ordered SpO2 goal is above 97%
• FIO2 needs ≤ 0.4
• Using inhaled pulmonary vasodilator via HFNC