What should you know about flow volume loops and asthma?

The graph maps how quickly air moves at different lung volumes while you breathe in and out forcefully. Asthma can cause variable narrowing of the airways, which may alter the expiratory part of the loop. A clinician compares the shape and measurements with your symptoms, examination and other testing; a single normal-looking loop does not settle every breathing concern. Wheezing, cough and chest tightness are common presentations of asthma, but they can also occur with other conditions.

Tell the testing team about current symptoms, recent infection, smoking or vaping, and every inhaler or medicine you use. Follow their instructions about treatment before the appointment. During the test, keep a firm seal around the mouthpiece, inhale fully, then exhale as hard and as long as instructed. Several coached efforts may be required. If a bronchodilator is used, the team may repeat the loop to compare the breathing pattern afterward.

Arrange clinical review for recurring wheeze, cough at night, activity-limiting breathlessness or chest tightness. Seek emergency care for severe breathlessness, blue or grey lips, confusion, collapse, or difficulty speaking in full sentences. If a prescribed reliever is not easing a flare as your action plan says it should, follow that plan and obtain urgent help.

Ask whether your loop suggests variable airflow narrowing, whether repeat testing is needed, and how symptoms such as cough or wheeze affect the interpretation. Ask for a written asthma action plan, including when nebuliser treatment or emergency assessment is appropriate.