Cure4CF Update

“The number” – the changing landscape of lung function testing in cystic fibrosis

When we visited the Mater in Brisbane last year as part of our tour with Dr Lucy Burr we visited the lung function laboratory. Here we met Respiratory Scientist Grace Madden who talked to us about the changing landscape of lung function assessment in cystic fibrosis.  Keen to learn more, I caught up with Grace recently to talk about the changing landscape of lung function assessment for cystic fibrosis.

 This can take a lot of effort and can be really tiring for people with CF.  The result most people are familiar with is the FEV₁ – which stands for the Forced Expiratory Volume in 1 second, where forced expiratory means – how hard and fast you breath out and the volume in 1 second is the amount of air that was expired in the first second. This number is usually expressed as a percentage and is compared to a reference range so the team can see how your lung function compares to others the same age, gender, race and height. It’s important to remember that everyone’s lungs are different shapes and sizes, and normal results differ from person to person. Because of this, the team will often look at your own results over time, as this helps indicate how your lungs are doing compared to your baseline.

https://www.cfwa.org.au/wp-content/uploads/2021/12/Spirometry-2021.pdf  is a great resource on spirometry from CF WA if you would like to know more.

Why do I have to repeat the test so many times?

How has the importance of “the number” changed?

Grace explained that people in the clinic understand that when they do their lung function testing, if a low number was produced, this meant they had to cancel their plans and might likely be admitted to hospital.  Low numbers usually meant infections or some other issue that required hospitalisation to rapidly receive treatment. This meant that young people were often anxious about “the number” and of course, their families were also often anxious and worried, eagerly awaiting the result.

Advancements in CF care in terms of infection control and mucus management and now with modulator therapy being accessible for many people with CF have meant that for Grace and her team, spirometry is now easier and quicker to undertake.  People are feeling better and experience less coughing and are becoming less focussed on “the number”.  Now the focus is more about the change in the number between clinic visits, has it changed from last clinic.  If the change was a reduction in lung function, then the team will look at how big the change is and use other assessments to understand what has resulted in this change. Small changes are often nothing to worry about and can be part of the normal variation.

My lung function is “normal”, what does this mean for my lung health?

For many young people with CF now, lung function is often in the healthy range or “normal”.  While this is a life changing improvement it does offer some challenges for CF teams.  Grace and her team at the Mater are exploring new ways to be able to assess lung function and changes in lung health in this new era of normal lung function.  Some of the new techniques include the Lung Clearance Index (LCI) and Forced Oscillation Technique (FOT).

About the Lung Clearance Index

The lung clearance index (LCI) scores how well air moves though the lungs. It is very sensitive non-invasive and safe test that can detect early lung changes. It is measured by multiple breath nitrogen washout. Other than being able to pick up early changes in the lungs that may not be detectable by regular spirometry, this technique does not require a forced breath like FEV₁ and reduces the effort needed for the person with CF.  The other advantage of this technique is that it can be done easily with preschool age children who can enjoy a video while they are doing the test. This means it can easily be assessed during exacerbations as well during times of wellness. The person breathes in a tracer gas – often 80% nitrogen – and then breathes in 100% oxygen to wash the nitrogen out.  Nitrogen is the most abundant gas in the atmosphere and completely safe to inhale.  The regular air we breathe every day is 78% nitrogen.