HFNC is an oxygen therapy to provide high flow mixed air and certain FiO2 oxygen through soft nasal cannula to patient directly. Also known as nasal high flow oxygen therapy and high flow humidifier oxygen therapy.

High flow oxygen therapy has a unique physiological effect and widely used clinically to acute hypoxic respiratory failure, post-tube oxygen therapy, acute heart failure, chronic airway disease and some airway invasive manipulation. Especially to acute hypoxic respiratory failure patient, HFNC has obvious advantage in increasing PO2 than traditional oxygen therapy and better effect than NIV, also in comfort and tolerance. However, HFNC is recommended to be first choice respiratory treatment method for such patients.

Initially, HFNC is intended as an alternative supporting methods to NCPAP to be widely used for neonatal respiratory distress syndrome (NRDS), and obtained positive effect. HFNC application on adult has recognized the specific advantage during usage compared to usual oxygen therapy and non-invasive mechanical ventilation (NIV).

HFNC is with unique physiology effect

Traditional low flow oxygen therapy could provide max. 15L/min, it is lower than the actual flow patient requires. The insufficient flow will be filled by air, so the FiO2 will be diluted in unknown concentration. But high flow respiratory therapy device has built-in mixer unit that can provide maximum of 80L/min mixed flow, it is much higher than patient’s demand, to keep the constant FiO2, high to 100%.

HFNC can provide high flow air at 37℃ and relative 100% humidity, compared with traditional oxygen therapy, it has great superiority.

HFNC provides up to 80L/min air, this make it with function to flush nasopharynx dead space, make high FiO2 to reduce CO2, finally to increase SpO2 and reduce CO2.

Some investigators found HFNC could produce average 4cmH2O pressure, when mouth closed, the pressure up to 7cmH2O. So HFNC is with similar function to CPAP. But different to CPAP, HFNC is purpose to constant flow speed but not airway pressure, so in clinical usage, patient is required to keep mouth closed to reach better effect.

From most researches, HFNC is with good heating and humidification effect and convenient usage, HFNC is with better comfort and tolerance to high flow oxygen mask and NIV.