Respiratory / Lung Function Testing

What is a Respiratory or Lung Function Test (RFT/LFT)?

Respiratory or lung function tests are non-invasive diagnostic tests which provide feedback regarding the function of the lungs. Through the assessment of lung volumes, rates of flow, capacities, and gas exchange, RFTs provide useful information for doctors which can help in diagnosing certain lung disorders.

The normal values of RFTs vary from individual to individual. Some people need just one test, while others may require repeat tests so that results can be compared over time. Doctors may request an RFT as part of a routine health check, or to confirm/exclude the diagnosis of specific medical conditions such as asthma, chronic bronchitis or emphysema, or as part of the screening prior to surgery.

What does an RFT involve?

Prior to commencing the test, tight clothing may need to be loosened and jewellery removed. Patients will be sat either in a chair or a chamber for the procedure, and will be given a nose clip to wear to ensure breathing is restricted to the mouth only. Patients will be required to tightly seal their lips to a mouthpiece attached to the spirometer, and perform various breathing exercises. These exercises only involved inhaling and exhaling at various speeds and strengths.

Depending on the test requested, patients may be required to repeat these exercises several times, and may be given a bronchodilator after certain tests have been performed. Tests using a bronchodilator may be repeated after several minutes to test the effect of the medication.

Because RFTs are non-invasive, it is safe for most individuals. Side effects of RFTs may include feeling faint or light-headed due to hyperventilation, or an asthmatic episode precipitated by deep inhalation exercises, although these are rare and usually resolve within 10-15 minutes of the test. Some patients with a history of respiratory conditions, may feel tired after the procedure. There is generally no special care required after the procedure.

Preparing for an RFT

No special preparation is needed before the test, although patients should avoid using any inhalers on the day of the test, as this may interfere with results. If inhaler use is unavoidable, the technician should be informed of dosage and time of use prior to beginning the test.