Spirometry traces: what the breathing curves show

A trace records changing airflow as you inhale and then exhale forcefully. Its shape, size, smoothness, and repeatability help the clinician judge whether the manoeuvre was performed well. A cough, hesitation, early stopping, or air escaping around the mouthpiece can create an unreliable curve.

A lower or differently shaped trace may fit airway narrowing or reduced lung expansion, but the graph cannot be read in isolation. Asthma, COPD, bronchiectasis, a chronic cough, chest-wall problems, and testing technique can all affect results in different ways.

Listen to the instructions and use the same posture for every attempt. Seal your lips firmly, inhale as deeply as directed, then begin the blow immediately and continue until the clinician says to stop. More than one attempt is expected, and rest is allowed between blows.

Bring a list of medicines and mention smoking, a recent infection, chest pain, or an operation. Ask before changing inhalers or other treatment. If the printed curve worries you, wait for the clinician's explanation; a visual pattern is not a diagnosis by itself.

Get urgent help for sudden severe breathlessness, fainting, blue or grey lips, new confusion, or severe chest pain. Arrange prompt review when cough, wheeze, or shortness of breath is worsening, interrupts sleep, or makes routine tasks difficult.

Ask whether the curves met quality checks, which measurements are outside the expected range, and whether the pattern suggests a need for repeat testing. Ask how the trace relates to your symptoms and whether treatment or follow-up should change.