Spirometry
Spirometry is a non-invasive test that measures lung capacity and the airflow speed within the lungs. The procedure helps diagnose respiratory conditions or monitor the progression of diseases being treated.
General Description
Spirometry is a test used to check lung capacity and function. It measures the amount of air the patient can inhale and exhale, as well as the speed at which it is expelled (airflow velocity).
It is a non-invasive test used both to diagnose various lung diseases that affect breathing and to assess the progress of already diagnosed conditions. It is also commonly used in routine medical exams for occupational health or pre-surgical assessments.
When is it indicated?
Spirometry is performed for various reasons:
- The patient has difficulty breathing.
- There is a suspicion of lung diseases like asthma, chronic obstructive pulmonary disease (COPD), pulmonary emphysema, or chronic bronchitis.
- To evaluate if substances encountered in the workplace affect the person’s lung health (pneumoconiosis, silicosis).
- To check lung function before surgery.
- To assess whether a treatment is producing the desired effects.
- To track the progress of a lung disease.
This test is contraindicated in patients who have recently had a heart attack, pneumothorax, or a large thoracic aneurysm. It is also not recommended for those with respiratory infections, intracranial hypertension, vomiting, retinal detachment, or anyone who may have difficulty exerting the effort required to fully inflate the lungs and expel the air.
How is it performed?
The test involves exhaling into a tube connected to a spirometer, the device that measures lung capacity. This device collects the air and performs the necessary calculations to provide information about the volume, flow, and speed of the air.
Before starting the spirometry, a clip is placed on the patient's nose to prevent air from escaping. Then, the patient places the mouthpiece in their mouth and inhales and exhales gently several times. Afterward, the patient takes a deep breath to fully inflate the lungs and exhales forcefully and continuously until the specialist instructs them to stop, usually after about six seconds. The process is repeated several times.
A simple spirometry refers to a test that allows the patient to expel air at their own pace, while forced spirometry requires effort to expel air as quickly as possible.
In some cases, spirometry consists of two parts:
- Basal Spirometry: This is the procedure described earlier, without the use of medication.
- Spirometry with Bronchodilator: Inhaled medication, typically salbutamol, is administered to see if its effects cause any changes in the results.
There is a 15-minute interval between the two phases.
Risks
Spirometry does not cause any harm to health.
Some individuals may find it difficult to maintain exhalation for the required amount of time and may feel slightly dizzy after the test.
What to expect from a spirometry test
Spirometry is a non-invasive, painless diagnostic test that is typically performed on an outpatient basis, and normal activities can be resumed immediately afterward.
The patient remains seated during the test. First, a clip is placed on the nose, and the spirometer's mouthpiece is placed in the mouth. Care should be taken to prevent the tongue from blocking the opening and to seal the lips tightly around the mouthpiece to avoid air leakage.
The procedure is repeated three times without medication and the same number of times after medication is taken. The specialist uses the highest values as the test results. The patient may feel slightly dizzy after exhaling deeply several times, but this usually passes quickly after lying down with feet elevated for a while.
The spirometry test lasts between 15 and 30 minutes, although it may take longer when repeated with medication, as a 15-minute wait is necessary for the medication to take effect.
Although the doctor obtains the results immediately, they are typically provided to the patient after a few days for proper evaluation. Based on the results, spirometry can be normal, obstructive (indicating a narrowing of the airways that makes breathing quickly difficult but does not affect lung capacity), or restrictive (indicating that the lungs do not expand fully, reducing the amount of air that can be retained in the lungs).
Specialties in which spirometry is requested
Spirometry is a common procedure in allergology, pulmonology, occupational medicine, and family medicine.
How to prepare
To avoid altering the results of the spirometry test, it is recommended to avoid:
- Heavy meals before the test, although fasting is not necessary.
- Smoking, at least one hour before the test.
- Caffeinated beverages (6 to 8 hours before).
- Alcohol and tranquilizers (4 hours before).
- Intense physical exercise. The patient should remain seated for the 15 minutes before the test.
- Tight clothing that restricts the waist or chest, such as ties or girdles.
In most cases, medication used to treat lung conditions must be discontinued. The specialist will provide all necessary information a few days before the procedure.
