Spirometry loop

The loop is created as you breathe in and out through a mouthpiece. One part shows forceful exhalation and another shows inhalation. A smooth outline suggests that the manoeuvre was performed consistently, while a scooped or flattened outline can prompt the clinician to consider airflow limitation or an issue with the effort or equipment. The graph is not interpreted in isolation: age, height, symptoms, medication and the quality of the blows all matter.

Follow the operator's instructions closely. Sit or stand as advised, make a firm seal around the mouthpiece, inhale fully and then exhale with a fast, sustained effort. Repeat attempts may be needed to check consistency. Mention dentures, chest discomfort, recent surgery or a respiratory infection before starting. You can read about the test under [Spirometry](/treatments/diagnostics-and-screening/spirometry/) and the equipment at [Spirometer](/technology/spirometer/).

Stop the test and tell the operator if you feel faint, develop chest pain or become unusually breathless. Outside the appointment, urgent help is needed for severe breathlessness, blue or grey lips, confusion, fainting or inability to speak normally. A loop cannot decide whether symptoms are safe to watch. Persistent cough can have several causes; see information on [Chronic Cough](/conditions/chronic-cough/) and [COPD](/conditions/copd/).

Ask which part of the loop concerns the clinician, whether the recording met quality standards, and how the graph fits with your measured values and symptoms. Ask whether bronchodilator testing or another assessment is appropriate.