Spirometry

What is a Spirometry?

Spirometry is one of the commonest lung function tests performed in a respiratory clinic.

Lung function tests are used to assess how well you move air in and out of your lungs and well oxygen enters your body.

Spirometry is used to measure the rate at which the lung changes volume during forced breathing maneuvers. In simple terms, it measures how much air you can quickly breathe into and out from your lungs.

This test is done by having you take a deep breath and blow hard into a tube connected to a machine. Most patients can perform this test easily in the outpatient setting with coaching from a trained technician.

It is useful for diagnosing and monitoring respiratory conditions such as chronic obstructive pulmonary disease (COPD), asthma, pulmonary fibrosis. Spirometry can also detect early airflow obstruction in smokers who may have few or no symptom. In certain group of patients, it is also used to determine fitness for surgery and anesthesia.

Our spirometry test uses the flow sensing technique to detect the air flow.
Most spirometers display the volume-time curve and flow-volume loop graphs:

I. A volume – time curve



II. A flow – volume loop


In order to get an accurate result, before performing spirometry:

• Withhold some inhalation medications for 4 -24 hours (according to doctor’s advice)
• Do not smoke for at least 4 hours
• Do not exercise strenuously for at least 1 hour
• Do not wear tight clothing that may restrict the chest movement
• Do not drink alcohol for at least 4 hours
• Do not eat a large meal for at least 1-2 hours

Patient is seated comfortably for the test. A disposable mouthpiece is attached to the spirometer for the patient to perform the maneuver. Patient will be coached on the whole procedure before performing the test. Take a deep breath in through the mouth until the lungs are full. Blow into the mouthpiece as hard, fast and long as possible, until the lungs feel empty.

The procedure has to be repeated a few more times to get consistent results. A breathing medicine (bronchodilator) is sometimes given to find out how much better the patient might breathe with this type of medicine. The procedure usually takes 30 minutes to complete this test.

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