What is Spirometry?
Spirometry is an objective physiological lung function test, and it is one of the most important tools for pulmonary physicians to diagnose lung and airway conditions accurately.
What Conditions Can Spirometry Test Diagnose?
Typically, spirometry testing is used to diagnose asthma, chronic obstructive pulmonary disease (COPD), and other conditions that affect breathing. In asthma, spirometry is used to detect obstruction, the degree of obstruction, and the variability of obstruction.
If you’ve already been diagnosed with a chronic lung disorder such as asthma, spirometry may be used periodically to monitor your lung and airway condition and check whether a treatment for your asthma is helping you breathe better, or whether your breathing problems are under control.
What Does Spirometry Measure?
Simply put, spirometry measures how much air you inhale, how much you exhale, and how quickly you exhale.
Key spirometry tests include the following:
Forced Vital Capacity (FVC):
This is the largest amount of air that you can forcefully exhale after breathing in as deeply as you can. A lower-than-normal FVC reading indicates restricted breathing.
Forced Expiratory volume in 1 second (FEV1):
This is how much air you can force from your lungs in one second. This reading helps assess the severity of your breathing problems. Lower FEV1 readings indicate more significant obstruction.FEV1/
FVC Ratio:
The ratio between FEV1 and FVC is used in the diagnosis of restrictive or obstructive lung disease. For healthy people, it is above 70%. The value is reduced for asthmatics and COPD patients showing the presence of an obstruction in the lungs or airways. Different from FEV1 alone, FEV1/FVC ratio provides a relative indication of obstruction such as in asthma, and it is particularly useful in helping assess how well your asthma treatment or management is working or how your condition is progressing.
Peak Expiratory Flow Rate (PEF):
The maximum expiratory flow is an indication of the degree of obstruction in the airways. The value is reduced for asthmatics and COPD patients.
FVC, FEV1, FEV1/FVC, and PEF together provide a good picture of how well your lungs and airways function.
How to Prepare and Perform a Spirometry Test
To Prepare:
● You may need to stop using your inhaler beforehand. Check with your doctor.
● Wear loose clothing that won’t interfere with your ability to take a deep breath.
● Avoid eating a large meal or drinking alcohol before your test.
● Avoid smoking for 24 hours before the test.
● Avoid heavy physical effort or exercise for at least 30 minutes before the test.
To Perform:
● Sit in a chair with your back straight.
● Follow the instructions to put on a breathing piece.
● Take a deep breath in as far as you could, then hold your breath for a few seconds before exhaling as hard and complete as you can into the breathing piece.
● Repeat the test three times to make sure that the 3 test results are consistent, then record the highest value.
Spirometry Criteria For Normal Condition
The normal/health range of the spirometry results varies from person to person, they’re based on your age, height, race, and sex.
You can find your estimated normal values from relevant medical sources. Typically, for FVC, FEV1, and PEF, a ratio value of >= 80% of the estimate is considered normal. For FEV1/FVC, >= 70% is considered normal.
How to Use Spirometry to Diagnose and Manage Asthma
● To manage your asthma, we recommend that you perform spirometry testing periodically based on the severity of your symptoms.
● You could first find out your normal range for FVC, FEV1, and PEF.
● Record your spirometry results of FVC, FEV1, FEV1/FVC, PEF.
Spirometry Criteria for Asthma
● If the ratio of FVC, FEV1 and PEF results to your corresponding normal values are below 80%, or FEV1/FVC ratio below 70%, it is an indication of asthma.
● You should discuss with or visit your doctor for treatment or adjust the existing treatment.