Adult spirometer: what to know before a breathing test

The device records a forceful breath through a mouthpiece. A trained clinician interprets the measurements alongside your symptoms, medical history, examination, and sometimes other tests; a reading does not establish a diagnosis by itself.

During spirometry, the device measures the total amount of air forced out after a full breath and the amount expelled early in that breath. The relationship between these measurements can suggest narrowed airways or a reduced breathing volume. Results are compared with an expected range based on personal characteristics such as age, height, and sex.

You may repeat the test after using a bronchodilator inhaler to see whether opening the airways changes the readings. Good technique matters: a loose seal, hesitation, coughing, or stopping too soon can distort the result, which is why the clinician usually asks for repeated attempts. A diagnostic spirometer is different from an incentive spirometer used for guided deep-breathing exercises during recovery.

Follow the clinic's instructions about inhalers and other medicines; do not stop them unless the testing team specifically tells you to. Wear clothing that does not restrict your chest, avoid a heavy meal immediately beforehand, and bring your inhalers and current medicine list. Tell the team about a recent chest infection, heart problem, fainting episode, or surgery involving the chest, abdomen, or eyes because the forceful blowing may mean the test should be postponed.

At the appointment, sit upright, wear a soft nose clip, seal your lips around the clean mouthpiece, inhale fully, then blow out as hard, fast, and completely as instructed. Listen for coaching and repeat the manoeuvre when asked. If you use a home device, confirm whether it is meant to measure airflow or encourage slow deep breaths, and follow the device-specific cleaning instructions.

Stop the test and tell the clinician immediately if forceful breathing causes chest pain, marked dizziness, faintness, or severe shortness of breath. Brief coughing or light-headedness can occur, but the testing team should assess symptoms that are intense or do not settle promptly.

Seek emergency help for severe difficulty breathing, blue or grey lips, new confusion, collapse, or chest pressure, whether or not you recently used a spirometer. Arrange a medical assessment for ongoing breathlessness, wheezing, persistent cough, or a clear decline from your usual breathing rather than relying on a home reading alone.

Ask why spirometry is being recommended, whether to take your usual inhalers before the appointment, and whether a recent illness or procedure affects timing. Afterward, ask whether the attempts were technically reliable, how the pattern fits your symptoms, whether the bronchodilator changed the measurements, and whether you need another lung-function test, treatment review, or follow-up measurement.