High Flow Nasal Cannula: Positive Airway Pressure Explained

Today, I would like to talk a little bit about one of the more common oxygen delivery devices found in the Pediatric Intensive Care Unit and Pediatric Step-Down units.

It's called a High Flow Nasal Cannula, or HFNC for short.


Source: The Royal Children's Hospital Melbourne

It is a very similar concept to the slightly smaller nasal cannula that you are likely to be much more familiar with, however it is able to provide more support than the smaller regular nasal cannula.

To better explain exactly how it is helping your child's lungs, let me explain a little about how the lungs work.


Source: Patient.info.com

What is important to know about the above image are those little grapes in the bottom left corner, called alveoli. They exist inside your lungs and their sole job is to take the oxygen we breathe in and allow it to perfuse into the surrounding tissues, and then eventually into your blood to deliver oxygen to the rest of your body. In order for these alveoli to stay open correctly and long enough to do their job correctly, there needs to be enough pressure within your lungs to hold them open.

When your child is sick with anything from a virus, pneumonia, an asthma exacerbation, or any other form of respiratory distress, the ability of the alveoli to stay open is inhibited.

So: If the alveoli cannot stay open because the lung itself is sick, they cannot get enough oxygen to the rest of the body. In addition to medications that we can talk about later, doctors utilize high flow nasal cannulas to help with this exact issue. Not only do they provide oxygen, and at much higher amounts that regular nasal cannulas, but they also provide positive pressure into the lungs to allow the alveoli to stay open like they need to be.

Something else to keep in mind in regard to these high levels of oxygen is that with large amounts of oxygen, there needs to be large amounts of humidification. 20 liters of oxygen blowing into your nose would most certainly dry you out and would probably cause a very bloody nose. That is why there is water and a warmer hooked up to your child's HFNC. The water humidifies the air and the warmer helps it reach room temperature and slightly warmer so that your child can breathe easier. In the end, that warm humidification can also help with the congestion.

Source: Respiratorycare.com

Here is another look at the circuit itself with the warmer, water, and cannula.

So when your child is sleeping in that bed next to you, wearing this contraption and asking why they still need it, you will have the exact answer.

I hope this information helps you feel more empowered and in control of the situation. HFNCs are very common in the PICU and they really are amazing devices that reverse a lot of respiratory issues before they become emergencies.