Comprehensive Guide to Spirometry: Tests, Results, and Interpretation
Spirometry is a simple but effective diagnostic test that can help determine how well your lungs are working. It has an important role in diagnosis and follow-up of various respiratory diseases such as asthma, COPD, and pulmonary fibrosis.
With a look at how much air you can inhale and exhale — and how quickly you can do it — spirometry can help your doctor assess your breathing patterns and monitor the response to treatment, as well as diagnosis and manage lung diseases such as chronic obstructive pulmonary disease (COPD). If you suffer from persistent coughing or shortness of breath, are a long-term smoker, spirometry may provide valuable information about the status of your respiratory health.
Understanding the Spirometry Test Procedure
It is simple and non-invasive, and generally takes no more than 10 to 15 minutes. You may be told not to smoke, eat a large meal, do vigorous exercise, or take bronchodilators shortly before the test because these can affect the results.
For that, you will need to sit comfortably and utilise a disposable mouthpiece that is connected to a digital spirometer. You’ll take a deep breath in, and then blow out as hard and for as long as you can into the device. This step is repeated a few times to verify reproducible readings. The procedure is conducted by a technician or nurse, and you might get a bit light-headed – that is normal and it goes away.
Spirometry Interpretation: Key Measurements
There are three main values by which spirometry is interpreted:
- FEV1 (Forced Expiratory Volume in 1 second): Amount of air you can forcefully exhale in 1 second.
- FVC (Forced Vital Capacity): The volume of air which is breathed out during a forced expiration.
- FEV1/FVC Ratio (Tiffeneau): A ratio to help determine whether airflow is obstructed. A reduced ratio indicates that obstructive lung disease is present.
These readings are then compared against expected values for a person of your age, gender, height, and ethnicity, providing a snapshot of your lung health.
Normal Spirometry Values by Age
It’s natural for lung capacity to fluctuate over the years. Weaker correlation was observed in few years’ age group and this age group difference may be influenced by their age-specific or development-determined lung function: older children and young adults had generally greater values in FEV1 and FVC and losing gradually FEV1 and FVC due to normal ageing’s apoptosis.
Both FEV1 and FVC should be comprised between 80% and 120% of predicted values, in adults.
- Kids: Prices are all over the map and are reduced for age and size.
- Elderly patients: A slight decrease in FEV1 should be anticipated; however, marked reductions suggest the presence of disease.
Height, sex, and ethnicity play a role in determining what’s a ‘normal’ reading for each person.
Obstructive vs. Restrictive Spirometry Patterns
Spirometry is used to differentiate between two major types of lung disease:
- Obstructive pattern: They are typically present in diseases such as asthma, as well as COPD. Here, FEV1/FVC is less than 0.7, suggesting difficulty exhaling the air out completely.
- Restrictive pattern, encountered in the context of diseases such as pulmonary fibrosis or conditions such as scoliosis, is characterised by a decreased FVC with preserved or high FEV1/FVC ratio (normal, >70), reflecting limited chest and lung expansion.
Knowing the distinction can help doctors better refine treatment strategies.
Reversible Spirometry: Assessing Airway Responsiveness
In order to determine if the airway obstruction is reversible, your doctor will often re-measure the spirometry after you have been given a bronchodilator (a medication that affects the smooth muscle of the airways causing them to open).
If there is a substantial improvement of FEV1 post-medication, then there is reversible airway disease, e.g., asthma. Conversely, little or no reversibility may be suggestive of fixed obstruction (as in COPD). This test is the cornerstone of making a correct diagnosis and choosing appropriate treatment.
Conditions Diagnosed with Spirometry
The Importance of Spirometry in Specific Respiratory Diagnoses:
- Asthma: Demonstrates airflow limitation that is reversible and variable.
- COPD: Suggests that the obstruction is chronic and may worsen over time.
- Pulmonary fibrosis: Exhibits restrictive disorder with low lung volumes.
- Pre-surgical testing: Tests lung function before certain surgeries, especially in those having respiratory conditions.
Preparing for a Spirometry Test
Preparation is crucial for accurate results. You may be asked to:
- Do not take bronchodilators or caffeine on the day of the procedure.
- Do not smoke or perform vigorous exercise.
- Don loose-fitting clothes to facilitate easy breathing.
There are a few contraindications to keep in mind, including a recent heart attack, eye surgery, or active tuberculosis. Make sure you tell your healthcare provider about all the medical history that you have.
Limitations and Follow-Up Testing
Though spirometry supplies crucial information, it is not definitive. Other tests, such as DLCO (Diffusing Capacity of the Lung for Carbon Monoxide) or lung volumes, may be required to complete the evaluation.
Repeat testing is also helpful in management of chronic disease or to adjust treatment as lung function changes.
Conclusion
Spirometry is an important adjunct in respiratory medicine with the ability to provide clear measures of lung function and support the diagnosis and management of diseases such as asthma and COPD. It’s fast, safe, and very informative.
At Chase Lodge, we suggest that people with ongoing breathing symptoms or known risk factors such as smoking should have spirometry tests. If you are worried about your lung health, talk to one of our experts today to see whether or not spirometry is right for you.
