Lung function tests
By GAtherton

At this month’s patient support meeting Phil Langridge, Specialist Physiotherapist at Manchester University NHS Foundation Trust, Wythenshawe Hospital, gave a fantastic talk all about spirometry and lung function tests.

He started the talk with a simple question “Do you look forward to lung function tests?” An audience member offered a simple reply “No, it’s purgatory”.

Lung function tests are hard. The thing is, they’re maximum function tests. The staff carrying out the tests sometimes sound a bit strict, firmly telling you to keep going and put more effort in. The tests are tough, and for some people they can take a while to recover from. That’s because they need maximum effort and it can take a lot out of some people.

Phil gave us an overview of most commonly used tests, starting with the spirometry test. Sometimes these tests can be done at your GP surgery with a practice nurse in a familiar setting. Sometimes they have to be done in hospital and this can lack privacy and be a bit intimidating. Try not to worry, staff understand this, just tell them you’re feeling nervous and they’ll do what they can to help so your test gives the best result possible.


Spirometry is used to:

  • Detect respiratory disease
  • Measure bronchial responsiveness
  • Diagnose and differentiate between obstructive lung disease and restrictive lung disease
  • Assess impairment from occupational asthma
  • Conduct pre-operative risk assessments before anaesthesia or cardiothoracic surgery
  • Measure response to treatment of conditions which spirometry detects – including aspergillosis.


What do lung function numbers depend on?

Lots of factors influence lung function numbers including age, gender, race, height and weight.

You might be predicted a number that can give you a feel of where you sit in the ‘normal’ range.

But you mustn’t fixate on that number, your performance in tests can be affected by things that are nothing to worry about, for example, you might have had a rubbish night’s sleep, skipped breakfast, had to wait ages in the waiting room for you appointment, already seen the physio to get a sputum sample and THEN had to do lung function. Your performance might then be very different to another day where you walk straight into the test room having slept like a baby, had a full English and been the first person seen that day.


What do the tests measure?

FEV1. This is the forced expiatory volume in one second i.e. how much air you can empty from your lungs in the first second – this is a good measure of your airway obstruction, or how ‘floppy’ your airways are.  If it’s lower than expected, you might have airway obstruction. This is an important one to measure when doing drug effectiveness tests.

FVC. This is forced vital capacity and is the test where you’re blowing your hardest and the physio is shouting ‘Keep going! Keep going! Keep going!’ and you feel like you might pass out! FVC is the amount of air you can expel from your lungs in total and so you’re encouraged to ‘keep going’ because staff have to make sure you’re giving it your best and completely emptying your lungs so that the test result is accurate and meaningful.

You might have to wear a nose clip during FVC. This is so that you don’t release air through your nose which can give a lower result. You usually have to do FVC three times and an average result is taken, the machine you blow in to plots volume exhaled against time.

Peak Flow – How fast you can exhale. This test can be helpful as a monitoring tool for asthma but isn’t used that often in clinic.

The thing with these measurements compared to e.g. blood tests or CT scans is that they’re effort dependent. It’s important to remember that for the results to be meaningful and therefore informative and useful, you really have to do the best you can.

FVC can be lowered if you have an obstructive or restrictive condition. The ratio between FVC and FEV1 gives clues as to whether you have an obstructive condition or a restrictive condition and can help to diagnose conditions such as COPD.

A healthy person will have a ratio of around 80%, i.e. when they empty their lungs, 80% of air will be expelled in the first second, but if you struggle to get the air out because of obstructed or floppy airways it takes you longer to empty them, it may be lower. If it’s 70% or less it might be COPD.

Doing this at the GP can help to diagnose without having to send people to a specialist centre with all the extra costs of travel and parking and the extra anxiety of being in an unfamiliar setting. Lots of GP surgeries now have nurses who can do spirometry to help with COPD diagnosis.

The frequency of tests can vary too, depending on your condition, what treatment you’re on, if you’re changing treatment, if you’re having survey. If you’re stable with COPD and asthma and you’re being managed by your GP, you might only have lung function tests every 5 years or so. It’s very variable.

Here’s a top tip from Phil! Ignore your lung age if you’re told it! It’s scary and meaningless!

Phil is 41 years old, he is healthy, he doesn’t have lung disease, he cycles to work and he plays for the first team at his hockey club regularly. His lung age came out at 54!

That sounds scary! If you’re told it, it might make you feel very worried. We have patients who visit our clinic who have a lung age of 150 and they’re stable and have had that value for years and years. It really doesn’t mean anything.

Why might people be told it then? Well, it might go back to persuading people to stop smoking, it might scare people into quitting smoking if they’re told they have the lungs of a 90 year old but they are only 60. But this can back fire and be quite nihilistic, people might think ‘oh well, my lungs are shot to pieces already, no point in doing anything to ty and help, I’ll just carry on as I am’. It’s not a helpful measure at all.


Some of the questions from the session:

Can you expand the lung having had a lobe removed due to an aspergilloma?

After thoracic surgery you might be put on an enhanced recovery programme. You may be given an incentive spirometer to encourage you to take slow deep breathes. Deep breathing and exercise such as brisk walking can really help with recovery from surgery too.


Do you need to worry about bleeds when you’re doing lung function tests?

Deep breathing will not cause your lungs to bleed but your clinic will always be careful if you are known to have thin walled lung cavities.

Watch Phil’s talk and let us know what you think!