Asthma and spirometry

You breathe through a mouthpiece connected to a spirometer, take a full breath in, then blow out as hard and completely as instructed. The manoeuvre is repeated so the clinician can check that the efforts are usable and consistent. Testing may be performed before and after an inhaled bronchodilator. A clear improvement after the medicine can support an asthma diagnosis, but results are interpreted alongside symptoms, examination and medical history. Normal spirometry between episodes does not by itself exclude asthma.

Follow the testing service's instructions about inhalers because the correct timing depends on the purpose of the test and your prescribed medicines. Do not withhold an inhaler if doing so conflicts with urgent symptom care; tell the team what you used and when. Wear clothing that does not restrict a deep breath, avoid a heavy meal immediately beforehand, and bring your inhalers and medicine list. Tell the clinician about a recent chest infection, surgery, heart problem, fainting with forced breathing, or pregnancy before starting.

Spirometry is generally arranged as a planned assessment, not as the response to a severe asthma attack. If you are acutely unwell, the clinical team may postpone forceful breathing and assess you another way. Seek emergency care for severe breathlessness, difficulty speaking, blue or grey lips, confusion, exhaustion, or symptoms that do not improve after following your asthma action plan. During the test, tell the operator immediately if you develop chest pain, marked dizziness or feel faint.

Ask whether the test quality was adequate, whether airflow narrowing was present, and whether the bronchodilator changed the measurements. Clarify how the findings fit your symptom pattern and whether repeat testing, monitoring at home or another assessment is needed. If treatment changes, request a demonstration of inhaler technique and an updated written asthma action plan.