HFNC(High flow nasal cannula or High flow nasal therapy):-
High flow nasal cannula (HFNC) is an oxygen supply system that supplies up to one 100% of humidified and heated oxygen at a fluid rate of about 60 per minute. High flow nasal cannula is not a regular nasal cannula that is cranked up to very high flow rates. The High flow nasal cannula machine actually takes gas and can heat it to 37 degrees Celsius, with a 100 percent relative humidity, and can deliver 0.21 to 1 percent by volume fio2 at flow rates of up to 60 liters per minute. Based on patient flow and fi02 requirements, flow and fi02 can be independent titrated.
How to use a HFNC machine?
Hfnc machine supplies high flow oxygen to the patient (At high risk of serious respiratory failure or mechanical ventilation, a closely monitored setting is usually necessary). However, HFNC may be delivered in a less monitored setting as soon as the patient improves and reduces the oxygen requirements in the trajectory.
There are two parameters to be set:
- The FiO2
- And the flow rate
Firstly doctor set the flow rate of high flow nasal oxygen at 20 to 35 L/minute. The HFNC flow rate can be anywhere between 5 and 60 L/minute. After that medical team set the FiO2 (range 21% to 100%) for the desired peripheral oxygen saturation. The flow rate can then be increased by five or ten L/minute if the breathing rate does not improve, oxygenation does not improve adequately. The rise of flow and FiO2 both will lead to improved saturations of peripheral oxygen; first, prefer to maximize the flow rate in order to maintain FiO2 to sixty percent; but to achieve an appropriate oxygenation an increase of the FiO2 can also be necessary.
Finally, once the flow rate reaches ≤20 L/minute and the oxygen concentration increases to fifty percent, the patient will switch to a standard low nasal cannula system.
Benefits of HFNC:-
1)Precise oxygen delivery at high flow rate:-
Using high flow nasal cannula allows oxygen to be delivered to the patient's airway more accurately at high flow rate, and unlike conventional systems, which may entrain indoor air. Respiratory distress patients generate high inspirational flow rates that exceed the flow rate of standard oxygen equipment, resulting in room air intake and a reduction in the delivery of the set fraction of inhaled oxygen (FiO2). Generally, the flow rate in HFNC exceeds that of the patient, resulting in very little indoor air and a more reliable FiO2. High flow rates have also been shown to improve respiratory patterns by increasing mare volume and reducing respiratory rate.
2)Soft nasal prongs:-
HFNC nasal prongs are generally soft, but rigid in the hard plastic. Various studies indicate improved patient comfort with high-flow nasal cannula (HFNC) compared with conventional low-flow oxygen delivered through nasal cannula or oxygen provided through a face mask.
3)Humidified and heated high flow nasal oxygen:-
Standard nasal oxygen therapy is cold and dry (not warmed) Standard oxygen treatment (not humidified) that can increase airway resistance. In addition, a substantial amount of calories can also be used in individuals during normal oxygen therapy to warm and humidify gas.
While high flow nasal cannula machine(HFNC) is used to warm to 37 degree Celsius and humidify, which can then decrease the airway inflammation, maintain the mucociliary function, improve the mucous clearance, and reduce the caloric consumption in inpatients with respiratory failure. Thus, high flow nasal cannula devices are better at heating and humidifying inspired oxygen, compared to the oxygen masks or standard nasal oxygen therapy (flow rate typically 10-15 L/min).
4) Washout of Dead-space:-
The washing of dead space from high airways can improve ventilation efficiency and enhance the delivery of oxygen. Due to continuous flow at high rate HFNC washes out the patient’s pharyngeal dead-space. Each breath the patient takes now will be a wash out of carbon dioxide, replaced with an oxygen, which will improve breathing efficiency.
