Nasal cannula for oxygen therapy: what it is, how it is made, when to use it
The nasal cannula is an instrument used to support respiratory activity (artificial ventilation) during oxygen therapy
Oxygen therapy refers to the administration of oxygen to the patient for therapeutic purposes, as part of a therapy in cases of chronic respiratory failure (such as in chronic obstructive pulmonary disease, chronic bronchitis, asthma and some cancers) and acute respiratory failure (such as in emergencies, trauma, shock).
When is oxygen therapy used?
Oxygen therapy in general is necessary in all situations involving a reduction in oxygen levels (PaO2) in the blood.
The nasal cannula, in particular, is particularly suitable for chronic home oxygen therapy, i.e. done at the patient’s home or outside the hospital, where low oxygen flows are required.
The pathologies in which it is usually used are:
- chronic obstructive pulmonary disease (COPD);
- chronic bronchitis;
- asthma;
- bronchiectasis;
- interstitial disease;
- advanced cardio-respiratory insufficiency;
- advanced-stage tumours;
- advanced neurodegenerative diseases;
- cystic fibrosis;
- pulmonary emphysema.
What does a nasal cannula look like?
The nasal cannula consists of two small tubes that are inserted into the nose and secured by their passage behind the ears and under the chin, where the nasal cannula is connected to a cannula, which, in turn, is connected to the oxygen supply source as a reservoir of oxygen in gaseous form (cylinder).
The cannula can vary in length, e.g. 5 or 10 metres.
A similar operation is that of the O2 probe or O2 tube, but with a single tube that must, however, reach deep into the nasopharynx.
The patient, in the case of a nasal cannula, must breathe through the nose and not through the mouth.
Advantages and disadvantages of the nasal cannula
The nasal cannula delivers low flows: 0.5 to 4-5 l/min, however, thanks to it, the patient can speak, eat or drink and is usually comfortable.
If the ends entering the nostrils are too uncomfortable, they can be shortened with a pair of scissors.
Increasing flow by 1 litre of oxygen per minute through nasal cannulae generally corresponds to breathing air with an oxygen concentration of 24%; adding 2 litres of oxygen to a concentration of 28%, and so on, adding 4% for each additional litre of oxygen to the ambient air concentration (which is 21%).
High-flow nasal cannula
The high flow nasal cannula consists of a compressor unit, a mixer, an active humidifier, a heated circuit and the end piece – made of soft, thick silicone – which is placed in front of the patient’s nostrils.
The aim is to deliver humidified and warm oxygen with adjustable FiO2 through flows of up to 60 l/min.
This oxygen therapy has the benefit of reducing anatomical dead spaces, providing a constant and adjustable FiO2, guaranteeing good humidification, but above all giving a PEEP effect (positive end-expiratory pressure that recruits the alveoli by improving exchange).
It is often used in intensive or sub-intensive care because it is a good alternative to non-invasive ventilation.
Comfort is often not ideal for the patient, but clinical results are excellent.
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