NASAL HIGH FLOW OXYGEN THERAPY

A LEARNING RESOURCE FOR INTENSIVE CARE NURSING STAFF

Mairi Mascarenhas

Clinical Educator ICU

Raigmore Hospital

Date last reviewed: 16 April 2018

What is Nasal High Flow Oxygen Therapy?

Patient needs and optimal outcomes: The combination of optimal humidity with nasal cannula allows a greater level of respiratory support than traditional nasal cannula, delivering high flows effectively and comfortably.

Contributing to this is the provision of four key benefits:

1. Delivers up to 100% accurately: with NHF, the aim is to meet or exceed the patient’s normal inspiratory demand, creating minimal air dilution. NHF can more accurately deliver prescribed oxygen concentrations at high flows providing more versatility and continuity of care as patients wean or their condition becomes more acute. This greater flexibility eliminates the need to switch between oxygen therapy delivery systems.

2. Flushing of anatomical dead space: with the delivery of high flows directly into the nares, a flushing effect occurs in the pharynx. The anatomical dead space of the upper airway is flushed by the high incoming gas flows. This creates a reservoir of fresh gas available for each and every breath, minimising re-breathing of carbon dioxide.

3. Positive airway pressure throughout the respiratory cycle: mean airway pressure throughout the respiratory cycle has been shown to be elevated with the delivery of the NHF. The degree of pressure is likely to be dependent on a number of variables including flow rate, geometry of the upper airway and whether the patient’s mouth is open or closed.

4. Optimised mucociliary clearance: optimal humidity emulates the balance of temperature and humidity that occurs in the healthy lungs, maintaining mucociliary clearance. This can be particularly important for patients with secretion problems such as those with chronic obstructive pulmonary disease. By delivering optimal humidity, drying of the airway is reduced, which maintains the function of the mucociliary transport system, clearing secretions more effectively and reducing the risk of respiratory infection.

1.

Nasal High Flow (NHF) is a respiratory care therapy that

delivers high flows of blended oxygen up to 60 litres

through a unique Optiflow nasal cannula.

This allows comfortable, effective delivery of up to

100% oxygen, creating an ideal solution for hypoxaemic

patients in mild to moderate respiratory distress.

Optiflow Nasal High Flow:

This is made up of four main parts:

1. Air/oxygen blender

2. Heated humidifier

3. Single heated circuit

4. Nasal cannula

Patient benefits:

Provides improved comfort compared to conventional oxygen delivery devices.

Reduced skin breakdown when compared to NIV.

Patient is able to eat, drink, talk, sleep.

Prevention of invasive ventilation.

Prevention of post-extubation respiratory failure and re-intubation

Cautions for use:

Contraindications or complications are rare in adults.

Abnormalities or surgery of the face, nose or airway that preclude an appropriate-fitting nasal cannula.

Some experts avoid NHF in those following upper airway surgery to avoid the theoretical risk that the high pressure may precipitate a venous thromboembolism or precipitate anastomic breakdown in patients with a high anastomosis. Check with Consultant responsible for the patient’s care and document the consultant’s decision.

2.

Mechanisms of NHF actions that improve patient care and patient outcomes:

Reduction of dead space:

Clearance of expired air in the upper airways.

Reduces re-breathing of gas with high CO2 and depleted O2.

Increases alveolar ventilation

3.

Dynamic positive airway pressure:

Breath- and Flow-dependent airway pressure.

Promotes slow and deep breathing.

Increases alveolar ventilation.

“PEEP effect”

In general every increase of 10l/minute of flow yeilds approximately 0.7cm H2O of airway pressure when the mouth is closed and 0.35cm when the mouth is open.

How much pressure is generated?

4.

Effect of dynamic positive airway pressure: NHF reduces inspiratory resistance making inspiration easier and increases expiratory resistance prolonging expiration. This promotes deep breathing which increases alveolar ventilation.

Delivering optimal humidity:

1. Optimal humidity emulates natural balance of heat and moisture that occurs normally in healthy lungs.

2. Is essential to physiological stability in already compromised airways.

3. Humidity enables the comfortable delivery of high flow.

5.

Airway hydration:

Improves muco-ciliary clearance.

Conditioned gas reduces drying of the airway epithelium.

Helps muco-ciliary transport system by clearing secretions and reducing the risk of infections.

Observed benefits:

6.

High flow interfaces: Can be used in paediatrics:

Adaptor for tracheostomy tube

7.

Main components of the Fisher and Paykel Nasal Highflow with maxventuri blender:

1. Gas outlet: humidifier tubing is connected here.

2. Oxygen analyser.

3. Calibration button.

4. On/off button.

5. Air inlet: a Bacterial/viral filter is connected here.

6. Oxygen control.

7. Flow control. Assembling the system:

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Instructions:

1. Slide the humidifier chamber on to the base.

2. Connect the short length of blue tubing to the grey port

marked “to patient” and attach the free end to the

humidifier chamber.

3. Connect the longer length of blue tubing to the remaining

port on the humidifier chamber.

4. (a) insert the heater wire cable into its socket.

(b) next insert the temperature and flow probe which is

inserted near the humidifier chamber.

(c) the remaining temperature probe is connected at the

end of the longer length of blue tubing.

5. Connect a bag of sterile water using the spike from the ater

feed tubing.

6. Attach the bacteria/viral filter to the grey port marked “air

inlet”.

7. Switch on humidifier and select temperature for invasive

mode i.e. tube icon. After warming up, the temperature

displayed should approximate 37°C.

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4a 4b 4c 4d

After assembling the system, the flow meter lever needs to be turned on:

Calibrating the system: For calibration in room air: Refer to images below -

1. Pull oxygen sensor out and hang in upright position.

2. Wait for approx 2mins to allow the sensor to equalise.

3. Press and hold the calibration button until the screen displays “CAL” (takes approx 3 secs).

4. When calibrated the numerical value displayed is 20.9%. The system is now ready to use.

9.

Ensure that the blue

flow meter lever switch

is in the correct position.

This enables the ball

bearing to rise when the

flow control is turned

counter-clockwise.

‘On’ Position ‘Off’ Position

Important:

After removing the oxygen

sensor it is important to wait

approx 2 mins before

proceeding to the next stage.

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Troubleshooting Error Alarms

Screen Error

Error correction

E02

Disconnect & reconnect the sensor lead

E03

Try re-calibrating

E04

Replace batteries

CAL Err St

Wait for thermal stability or stability in gas concentration

CAL Err lo

Repeat calibration 3 times, if same error occurs then

replace sensor

Explain the procedure to the patient and attach the appropriate interface

Nasal interface:

The nasal cannula is available in 3 sizes: Small, medium and large.

Standard size is medium and will suit most patients.

The prongs should accommodate ½ the diameter of the nares.

Small size is suitable for children as long as the prongs are half the size of the nares.

Tracheostomy interface:

▪ Can be used together with closed suction system. ▪ Attach to side-port connection on the closed suction system.

10.

Guidelines for commencing treatment:

As a starting point, the following are recommended:

1. Turn the flow control counter-clockwise. The ball-bearing on the flow meter will rise.

2. Turn the flow control until the ball-bearing rests at 30 litres per minute.

3. Ensure that you observe the ball-bearing directly at eye level.

4. Turn the oxygen control counter-clockwise to the desired concentration.

5. Observe the patient’s response and check comfort level - ask “How does it feel?”

6. Increase oxygen concentration as required to target oxygen saturations > 90% or as directed by Medical Staff.

7. If after 10 minutes, oxygen saturations remain suboptimal, increase the flow rate to 40 litres per minute.

8. If after another 10 minutes, oxygen saturations remain poor, increase the flow rate to 50 litres per minute. Increase further to 60 litres/min as required.

9. Obtain blood gas sample 1 hour after commencing therapy.

10. For adults, do not run the flow rate below 30 litres per minute.

11. Maximum flow rate for premature and neonatal cases is 8 litres/min.

12. Maximum flow rate for infants is 20 litres/min.

13. Maximum flow rate for paediatrics is 25 litres/min.

Record and document the following on the patient’s observation chart:

The flow rate that is being delivered.

The O2 concentration that is being delivered.

The humidifier temperature displayed & check that sufficient water remains in the bag.

Remember to always select the tube mode temperature setting when using this system. This means that the temperature displayed should approximate 37°C.

11.

Commence higher flow rates e.g. 40 litres if the patient is requiring > 50% oxygen and especially if

oxygen saturations are < 90% - check with medical staff acceptable O2 saturation parameters.

Each time the flow rate is increased, the display unit will show that the oxygen concentration has

reduced slightly. The oxygen control will need to be turned counter-clockwise again to increase

it to its previous setting.

Changes that need to be made if the patient requires nebuliser therapy: The nasal high flow system can be used at the same time as nebuliser treatments but the following need to be considered:

Nebuliser flow needs to be at least 8 litres per minute.

Nasal high flow therapy can be used in conjunction with nebulisers but the nasal high flow rate must be adjusted.

The maximum recommended flow including the nebuliser flow rate must not exceed 25 litres per minute otherwise the nebuliser treatment will be ineffective.

Example:

The patient is receiving nasal high flow therapy and the flow rate is 50 litres/min.

Nebuliser therapy is prescribed and the flow rate required is 8 litres.

This means that the nasal high flow therapy rate must be reduced to 17 litres per minute.

The oxygen concentration may need to be temporarily increased during treatment and reduced when the nebuliser is completed.

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