Piston spirometer: what to know

A piston spirometer contains a movable piston that responds to the air you breathe into a mouthpiece. The movement is converted into measurements such as the amount of air exhaled and the speed of exhalation. A nose clip may be used so air does not escape through the nose. The test can help investigate breathlessness, cough or wheeze and can support assessment of conditions such as asthma or chronic obstructive pulmonary disease. It does not by itself provide a complete diagnosis.

Wear comfortable clothing and follow the clinic's instructions about inhalers, smoking, meals and strenuous activity. Tell the clinician if you feel unwell, have chest pain, recently had surgery, or find it difficult to seal your lips around the mouthpiece. During each attempt, sit upright, take the requested deep breath and seal your lips firmly before blowing as hard and as long as instructed. Several attempts may be needed for a reliable result.

Tell the clinician immediately if the manoeuvre causes chest pain, faintness, marked breathlessness or wheezing that does not settle with rest. Seek urgent care for severe breathing difficulty, blue lips, confusion or inability to speak in full sentences. A test result that is outside the expected range should be discussed with the clinician rather than interpreted alone.

What are you measuring in my result? Should I use my usual inhaler before the test? Will I need repeat Spirometry, and what symptoms should prompt earlier review?