What to expect from spirometry for asthma

Expect breathing manoeuvres into a spirometer that measure how much air you move and how quickly you can blow it out. You will sit upright, wear a nose clip if needed, seal your lips around a mouthpiece and follow the technician's instructions. You take a full breath, then blow out as hard and as long as you can. The manoeuvre is repeated so the team can obtain reliable readings.

Asthma can narrow the airways and make it harder to empty the lungs quickly. Spirometry may show an obstructive breathing pattern, and the test may be repeated after an inhaled reliever. Improvement after the medicine can support an asthma diagnosis, although a normal result does not always exclude asthma when symptoms come and go. Your clinician combines the readings with your symptoms, examination and medical history.

Follow the appointment instructions about inhalers, because some medicines may need to be paused while others should be taken as usual. Wear comfortable clothing and tell the team if you feel unwell, dizzy or unusually breathless. Strong blowing can briefly cause coughing or light-headedness; resting normally helps it settle. Bring your inhalers and a list of medicines, and ask when the result will be reviewed.

Seek urgent medical help if breathing becomes severely difficult, you cannot speak comfortably because of breathlessness, your lips look blue or grey, or your reliever is not easing a severe asthma flare. These symptoms need prompt assessment rather than waiting for a test appointment. For ongoing wheeze, night waking or reduced activity, contact your clinician to review your asthma plan.

Ask whether you should change any inhaler before testing, whether a reliever response will be checked, and what each reading means for your asthma plan. You can also ask whether another breathing test is needed if symptoms continue despite a normal spirometry result.