Lung function testing: a guide for patients

PATIENT EDUCATION

Lung function testing: a guide for patients

Lung function tests are breathing tests that help us understand how well your lungs work. They measure airflow, how much air your lungs hold and how well gas passes from the lungs into the blood.

Illustration of a seated patient breathing through a mouthpiece with a nose clip during lung function testing, guided by a technologist.
AI-generated illustration of seated lung function testing; not a photograph of the practice or a patient.

Why might I need these tests?

They can help investigate breathlessness, wheezing or a persistent cough, support the assessment of conditions such as asthma and COPD, and monitor changes or the response to treatment.

What do the different tests measure?

  • Spirometry: how much air you can blow out and how quickly. Sometimes this is repeated after an inhaler to check for a change.
  • Lung volumes: the amount of air in your lungs, including air remaining after breathing out. Body plethysmography measures this while you sit in a clear booth, which is different from the seated setup pictured above.
  • Gas transfer (DLCO): how efficiently gas crosses from the air sacs into the blood, using a small amount of test gas and a brief breath-hold.

What happens during testing?

A technologist guides you through breathing into a mouthpiece while wearing a nose clip. You may be asked to breathe normally, take a deep breath, hold your breath or blow out firmly. Measurements are repeated to check their reliability. Tell the technologist if you feel dizzy, uncomfortable or need a break.

How should I prepare?

Wear comfortable clothing and follow the instructions supplied with your appointment. Bring your inhalers and a list of medicines. Only withhold inhalers if your treating team asks you to. Let the practice know about a recent chest infection, surgery or new health problem before attending.

Your specialist will explain the results alongside your symptoms and other investigations. Not everyone needs every test.

Questions, bookings or referrals

Referrals are welcome by phone on 044 803 2497 or by email to reception@dredgar.co.za. All referrals are screened to triage urgency, and an appointment will be promptly arranged.

This is a general overview. Follow the preparation instructions provided by your own care team.

Further reading: Cambridge University Hospitals: Full lung function test and NHS: Spirometry.