What is a lung function test, how to test it & what does it show?

According to UK government statistics, one in five people are diagnosed with respiratory diseases and it is the third leading cause of death. Lung health is important as our lungs are needed to provide our cells with the oxygen that they require to live.

A lung function test can detect problems with your lungs. This guide highlights what lung function tests are, what they show, and what the results may indicate.

What is a lung function test?

A lung function test, also called pulmonary function test, measures how well your lungs are working, and predominantly shows how well your body can breathe and deliver oxygen to the rest of the body. Lung function tests are typically done to diagnose lung conditions, or to monitor the status of an existing lung problem.

There are different types of lung function tests, the most common being:

  • Spirometry measures how much and how rapidly your body can move air in and out of the lungs. This is the most common type of lung function test, which is done by taking a full in-breath and then breathing out as hard, fast and as much as possible into a measuring device.
  • Plethysmography, also called lung volume test, assesses how much air is in the lungs after you take a deep breath and how much remains in the lungs when you breathe out fully. This is done by sitting in a see-through plastic box and breathing in and out through a mouthpiece.
  • Exercise stress tests measure the impact of exercising on lung function.
  • Gas diffusion tests assess how well your lungs can transfer oxygen from air breathed in into the bloodstream. This is done by inhaling a small, harmless amount of carbon monoxide, or other gas, and then taking measurements as you breathe in and out.

Lung function tests are simple and painless, and can be run together or by themselves depending on your condition or symptoms. Your GP may order an arterial blood gases (ABGs) test in addition to pulmonary function tests. This test measures the quantity of oxygen and carbon dioxide in your blood.

What does a lung function test show?

Lung function tests give a detailed assessment of lung function. The results take the form of measurable units, and can include the following:

  • Total lung capacity (TLC): This is the volume of air in your lungs when you breathe in as much as you can.
  • Forced vital capacity (FVC): This is the amount of air you can forcefully and quickly breathe out after taking a deep breath in.
  • Forced expiratory volume (FEV): This is the quantity of air you are able to expel from your lungs in 1 second (FEV1) and in 6 seconds (FEV6).
  • Lung Age: This is a calculation which can be made if you are a smoker. It compares your actual age with an estimated age based on the performance of your lungs.

An abnormal result can indicate one of two types of lung conditions:

Type of lung condition Description Examples
Obstructive Obstructive conditions entail a narrowing of the airways inside the lungs. This means that the lungs cannot completely empty its air content. Asthma, COPD, bronchitis, bronchiectasis, emphysema
Restrictive Restrictive conditions mean your lungs cannot fill in with air at full capacity. This is due to a loss of elasticity, which prevents them from fully expanding. Scleroderma, sarcoidosis, and pulmonary fibrosis.

Spine curvature, changes in the shape of the ribcage and obesity can also cause restrictions.

Depending on the test undertaken, the results of a lung function test can be available either immediately or within a few days.

What is a good lung function test result?

The results of a lung function test are scored against the normal range, which varies according to age, sex, height and ethnicity. Therefore, what is considered ‘normal’ lung function differs from person to person. Good lung function test results tend to range between 80% and 120% of the predicted total lung capacity (TLC) and forced expiratory volume (FEV1/FEV6). Results falling outside of this band could indicate a problem.

How long does a lung function test take?

Most lung function tests typically take between 10-15 minutes. This can however take longer if your GP wishes to do more than one type of test, or measure responsiveness to medication.

How do you know if your lungs are healthy?

There are many people living with undiagnosed lung conditions in the UK, and the best way to check your lungs are healthy is through a lung function test. While you may not realise you have a lung condition, some of the symptoms that may indicate a problem are:

  •       Wheezing
  •       Chronic cough
  •       Tightness in the chest
  •       fatigue
  •       shortness of breath

However, many conditions associated with lung function are symptomless, particularly in the early stages. Therefore a lung function test is the most accurate way to assess your lung health whether you have symptoms or not.

How can I get a lung function test?

At Bluecrest, we offer a range of packages that include lung function tests, so you can easily have your lung health assessed.

You can book a health check with one of our Health Assessment Specialists at one of over 2,000 mobile clinics nationwide, set in comfortable meeting rooms within carefully selected hotels and conference centres. Our Complete Health MOT Package includes a lung function test, in addition to a wide array of health markers for a detailed view of your health. These range from liver and kidney function measurement, stroke risk, full blood counts, cholesterol levels, blood pressure and diabetes screening.

You can also book a lung function test separately if you do not wish to have any other readings.