Cannula without filter – a good idea?

Main function of the filter

As I have already described in my e-book, the filter that is inserted into the connector of the cannula has two essential functions:

Protection against foreign bodies

The filter protects the lungs from foreign objects, fine particles in the air, bacteria, viruses, pollen, etc. These enter the lungs unfiltered. These enter the lungs unfiltered and can cause serious illnesses. The protective cloth is not a sufficient substitute for this.

Moisture enrichment

The filter enriches the breathing air with moisture so the airways do not dry out. This protects them and makes it easier to cough up secretions.
Because the windpipe is constantly dry, the risk of inflammation in the windpipe is much higher than without a filter. The trachea lacks the natural ability to regenerate and is constantly exposed to dry air – which naturally continues in the lungs. The lung secretions that we normally cough up can adhere to the mucous membranes of the windpipe because they are too dry to be coughed up. In the long term, the trachea and lungs can become inflamed. It can also lead to constrictions in the windpipe.

But is there more? Does the filter have any other functions? What happens if I leave out the filter?
In this blog, I would like to go into this in more detail and clarify how important it is to use it around the clock.

Further properties of the filter

In addition to the above “main functions”, several other features are often overlooked or related to the main functions.

Respiratory resistance and respiratory muscles

One of the main reasons for not using the filter is the natural resistance that the filter exerts when inhaling and exhaling. This is particularly unpleasant when inhaling if you are already at the limit of your breathing muscles.

I felt this for the first time after my last operation, when my diaphragmatic nerves no longer wanted to work, and the diaphragm no longer supported my breathing. At that time, my breathing was not working correctly, especially when I was lying down, which is why I needed the support of a ventilator.

We usually breathe in through our nose. The air must be sucked into the lungs through the nose. This involves overcoming a specific path via various “obstacles”, such as the nose, the pharynx, the larynx with the vocal cords and the windpipe. This path is a natural resistance that the respiratory muscles must overcome for sufficient air to flow through the lungs. A healthy person breathes approximately—500 ml per breath at rest. During physical exertion, it is approx. 3 litres. We breathe in and out 10 – 15 times per minute. The values are even higher for competitive athletes.

These breaths train our lungs in a natural way, constantly and imperceptibly for us – we simply breathe. However, if this resistance is eliminated by having only the opening of the cannula with direct access to the lungs, the respiratory muscles have to overcome very little resistance. And like any muscle that is not exercised, the entire respiratory musculature becomes weaker. And this can have a very negative effect – especially in the case of infections.

If you have been breathing without a filter for a long time and want to use it again, this can become a real challenge due to the lack of breathing muscles. You need to start breathing with the filter in small steps and train your breathing muscles again by using the filter for longer and longer periods. The best way to start is sitting down.

I experienced the importance of training myself through consistent breathing training. I will write my e-book or blog about this. I will create the content together with my respiratory physiotherapist. That will be a very exciting topic.

Moistening the cannula

It is also essential for the cannula to have moist, breathing air flowing through it, as this allows secretions in the cannula to be coughed up or suctioned out. If this is hardened, it is essential to clean the cannula, as this can significantly impair the air flow rate. In the worst case, you risk clogging the cannula, which is not very amusing

Prevention of chronic respiratory diseases

Suppose you do not sufficiently protect your lungs by using the filter to simulate a natural breathing process. In that case, you risk constant infections and inflammation and long-term chronic respiratory diseases such as bronchitis, pneumonia, asthma, etc.

Prevention of a reduced quality of life

The restriction of breathing inevitably leads to a deterioration in the quality of life.
You are immediately at the limit of your performance with the slightest exertion and risk needing constant oxygen or even artificial respiration. I was already dependent on both.


I will summarise the most important functions of the filter again here:

  • The filter prevents foreign objects from entering the lungs
  • The filter humidifies the air we breathe as our natural airways do. This moistens the trachea and cannula.
  • The filter trains the respiratory muscles by increasing the breathing resistance.
  • The filter prevents chronic respiratory diseases.

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