FORCED EXPIRATION TECHNIQUE (FET/HUFFING)

 Changing the way the air goes out

 To move mucus there needs to be enough airflow (movement of air) over the mucus to unstick it from off the walls of the airways and up towards the mouth. Care must be taken not to force the air out too hard as this can cause the airway to narrow and sometimes close. It can also cause early or uncontrolled coughing which doesn’t help with clearance of mucus from the smaller airways. Some techniques to assist with airflow out of the lungs include huffing (a forced expiration technique). 

Huffing: This is one of the most important things to understand, learn and practice when performing airway clearance. Huffing involves taking a breath in followed by an active or forced expiration (breath out) with your throat (glottis) open. This action creates a controlled squeezing of the airways and faster airflow that helps move mucus up the airway.  To do a huff you need to take a breath in and breathe out fast enough with an open “0” shaped mouth as if to fog up a mirror. If you have an open throat and an open mouth with your head slightly upright, the sound of the huff will be an open sound. If your huff sounds wheezy and tight, it may mean you are being too forceful causing closing or shutting down of your airways. If this is the case you will need to adjust the speed, and force of your breath out and/or your head and mouth position. Sometimes it is helpful to use a circular tube supplied by your physiotherapist to assist in the huffing technique. Place the tubing into your mouth and perform the huff while the tubing is in place. You can use a tissue at about 20cm from your mouth to see if you are creating a useful flow of air out. The tissue should float up into the air and stay there for the duration of the huff. The better the flow of air out with the huff, the better your ability to move secretions up towards your mouth to clear easily. A clearing cough can be performed after a series of huffs if the secretions are now moved to large enough airways to cough out easily. 

You may need to do a series of huffs to move secretions up towards the mouth. You can actually change your breath in, breathing at different volumes to create the “squeeze” points along the airways and milk the secretions towards your mouth.  Start with a small breath in and then the active breath out with an “o” shaped mouth, repeat a few times and follow up with some relaxed breathing. Repeat the huff technique after each 2-3 huffs gradually increasing the size of your breath in.     

Imagine one of your airways is a tube of toothpaste and your mucus is the toothpaste

If you have toothpaste (mucus) right at the top of the tube (airway) you can squeeze the top of the tube (airways) and easily move the toothpaste (mucus). This is the same in the lungs. If you have mucus at the top of the lungs you can easily move it by performing a high-volume huff. This involves taking a deep breath and forcefully exhaling with the glottis (throat) open.

However, if you have toothpaste (mucus) at the very bottom of the tube (airway) and try to squeeze the top of the tube (airway) you will not get any toothpaste (mucus). To move the toothpaste (mucus) at the bottom of the tube (airways) you need to squeeze from the bottom and move it up higher in the tube (airway). To squeeze the tube (airway) from the bottom you need to perform a low volume huff.

Low volume huffing involves taking only a small breath in and then gently but actively exhaling through an open mouth until you can’t breathe out further. You can liken it to breathing out like you are fogging up a mirror. Your lungs may give you some feedback if your huffs are working and there is mucus present. The feedback may sound like a crackling sound at the end of your breath out. When you start to hear some mucus movement just as you breathe out it is a sign that the mucus has moved further up your airway and you should increase the volume of your huff.  

Mid volume huffing involves breathing in to a moderate volume and exhaling through an open mouth at a slightly faster rate than a low volume huff.  Similarly, when you start to hear crackling or similar feedback in the earlier parts of your breath out, it is a sign that the mucus has moved further up the airway and you should increase the volume of your huff.

High volume huffing involves breathing in up to a large volume and breathing out through an open mouth at a fast rate. It is a much shorter and sharper exhalation and should be reserved for when the mucus has moved up high and is almost ready to be coughed out.

Your physiotherapist can guide you about the most optimal way to include these techniques into your airway clearance routine. Remember you should include the forced expiration technique in all of your airway clearance routines, and if you are doing exercise as a form of airway clearance, be sure to use the huff during or after this session. 

If you huff is not being effective moving secretions, you may need to return to your airway clearance device/technique and/or inhalation therapy.