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Lung function testing

Lung function testing involves a range of tests to find out how well your lungs and breathing systems are working.

They offer consultants vital information about your lungs and renal functions, and provide vital information for subsequent treatment.

Doctor looking at screens with images from a lung function test
A lung function test (also known broadly as spirometry) involves a group of tests to check how well your lungs are working.
 
The tests are designed to measure the amount of air you can inhale and exhale, how efficiently your lungs can move oxygen into your blood, and how well your lungs respond to different kinds of stimulation.
 
These tests are very good at diagnosing lung diseases, monitoring the progression of lung conditions, and assessing the effectiveness of treatment.

A lung function test has a variety of uses, such as:

Diagnosing lung diseases

Conditions such as asthma, chronic obstructive pulmonary disease (COPD), and pulmonary fibrosis can be identified through these tests.

Monitoring disease progression

If you already have an existing lung condition, these special tests can track changes in your lung function over time.

Evaluating treatment effectiveness

By measuring how well your lungs work before and after treatment, consultants can use these tests to figure out the most effective treatment or therapy.

Pre-surgical assessments

Lung function tests can help assess your risk of complications before  you undergo any kind of surgery, especially if it involves the heart or lungs.

A lung function test works by measuring different aspects of your breathing. The most common types of lung function tests include:

Spirometry

This test measures the amount of air you can breathe in and out, and how quickly you can exhale. Spirometry is often used to diagnose conditions like asthma and COPD.

Lung Volume Test

This test measures the total amount of air your lungs can hold. The results also provide details about the elasticity of your lungs and chest wall.

Diffusion Capacity Test

By measuring how well oxygen moves from your lungs into your blood, this test is particularly useful for diagnosing lung tissue disease, such as pulmonary fibrosis.

Cardiopulmonary Exercise Tests (CPET)

CPET measures your lung and heart function during exercise. Our consultants use it to evaluate how your lungs and heart work together, as well as assessing exercise tolerance or unexplained shortness of breath.

A lung function test might be ordered for those showing signs of:

  • Shortness of breath
  • Persistent coughing or wheezing
  • Asthma
  • Chronic obstructive pulmonary disease (COPD)
  • Cystic fibrosis
  • Bronchitis, or inflammation of the bronchial tubes, often caused by infection or smoking

Lung function tests might also be ordered to assess your risk if you're scheduled for surgery involving the heart or lungs, or to assess lung damage from smoking or diseases such as lung cancer.

Most of the benefits of lung function testing involve detecting early symptoms of lung diseases or issues, before they become worse or potentially untreatable.

If you have a chronic lung condition, regular testing is a vital part of your programme to manage the disease more effectively by adjusting treatments as needed. Lung function tests also provide valuable information about any risk of complications during surgery or other medical procedures.

The cost of a lung function test depends on your individual circumstances. At the time of your appointment your consultant will discuss all options with you and ensure all your questions are answered.

Our fixed-price packages include the cost of your surgery and all appropriate aftercare appointments. However, any pre-surgery diagnostic tests and your consultant's outpatient appointment consultation fee are charged separately.

Our flexible payment options help you spread the cost of your payment across a time period that suits you.

Before your lung function test, your consultant will give you specific instructions to help make sure you get the most accurate results. Depending upon the tests involved, you may be advised to:

Avoiding smoking

You should refrain from smoking for several hours before the test, as it can affect your lung function.

Limit alcohol consumption

Drinking alcohol can impact your test results, so it’s best to avoid alcohol for at least a few hours before the test.

Wear loose, comfy clothing

Tight clothing can sometimes restrict your breathing, so it’s important to wear something comfortable that allows you to take deep breaths with ease.

Avoid big meals

Eating a large meal before the test can make it difficult to breathe deeply, so a light meal is recommended.

Medication

If you use bronchodilators (prescription medication, usually inhaled, that help relax and widen your airways), you may need to stop taking it beforehand.

When you arrive for your lung function test, you’ll be seated in a chair and may be asked to wear a soft clip on your nose to make sure all your breathing is done through your mouth.

Depending on the type of test, you may be instructed to:

Breathe normally

Some tests simply require you to breathe in and out at a normal rate.

Take a deep breath

For tests like spirometry, you’ll be asked to take the deepest breath possible and then exhale as hard as you can.

Hold your breath 

In some tests, such as the diffusion capacity test, you may need to hold your breath for a few seconds to measure how well oxygen is being absorbed into your blood.

Exercise

If you’re undergoing a cardiopulmonary exercise test, you’ll be asked to exercise on a treadmill or stationary bike while your heart and lung function are monitored.

The entire testing process is non-invasive and usually painless, though some people may feel dizzy or short of breath, especially during strenuous parts of the test.

After the tests, you can usually head home and resume your normal activities.

Your test results will be studied by your consultant, who will explain what they mean and what the next steps should be at your next appointment.

If the tests reveal any abnormalities, your consultant might recommend further tests, lifestyle changes, or treatments.

Lung function testing is generally safe and can be performed on most people, including children and the elderly. However, the following people may need to avoid certain tests or take special precautions:

Pregnant women

While most lung function tests are safe during pregnancy, your consultant may avoid certain tests or adjust them to ensure the safety of you and your baby.

People with heart problems

If you’ve recently had a heart attack, your consultant may postpone lung function tests until your heart condition is more stable.

Severe respiratory conditions

If you have a severe lung condition that makes it difficult to breathe, your consultant will most likely recommend a less strenuous test.

Recovery from the tests is usually straightforward, with most patients returning to their normal activities straight away.

If you feel dizzy or short of breath following the test, rest for a few minutes until you feel better. It’s also a good idea to drink plenty of water to stay hydrated, especially if you exerted yourself during the test.

Your consultant will study your results and take you through the findings in person at your next appointment. If anything unusual or abnormal appears in your results, your consultant will advise on next steps, and a suitable treatment pathway.

Content reviewed by Circle in-house team in January 2025. Next review due January 2027.

  1. Lung function tests, MedicinePlus
  2. Spirometry, NHS
  3. Spirometry, WebMD

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