What a Pulmonary Function Test Is and How One is Performed
Pulmonary Function Test or PFT is an umbrella term for the tests that are done to check the functioning of the lungs. The human body has one pair of lungs that are responsible for providing oxygen to the body and removing carbon dioxide as the person breathes in (inhalation) and out (exhalation) respectively.
The lung function test is a measure of parameters such as:
- Tidal volume (amount of air inhaled or exhaled during normal breathing)
- Vital capacity (total volume of air exhaled after maximum inhalation)
- Functional residual capacity (volume of air in the lungs after normal exhalation)
- Residual volume (total air left in the lungs after maximum exhalation)
- Total lung capacity (overall air in the lungs after maximum inhalation)
- Forced vital capacity (amount of air that can be forcibly exhaled after taking the deepest breath possible)
- Forced expiratory volume in 1 second (forced exhalation volume in one second, after taking a full inspiration.)
An abnormal PFT test result i.e. an abnormal value of any of the above parameters is indicative of impaired lung functioning, which is suggestive of the presence of a disease.
PFT for asthma diagnosis is also quite common.
PFTs are non-invasive procedures since no incisions to the body are required These tests aid in diagnosing the disease and also help physicians decide the further course of treatment.
A pulmonary function test is done in the following situations:
- When a person experiences symptoms like coughing, wheezing, breathlessness, or has an abnormal chest X-ray
- Monitoring of the progression of the condition in conditions such as:
- Chronic obstructive pulmonary disease (COPD): a condition that involves chronic obstruction of airflow to the lungs.
- Asthma: a chronic inflammatory disorder characterized by repetitive episodes of impaired breathing
- Interstitial fibrosis: a respiratory disorder that presents as scarring of cells in the lungs.
- Pulmonary vascular disease: a group of diseases that is related to the abnormal flow of blood between the lungs and heart.
- To check the treatment response in respiratory conditions like COPD, asthma, and bronchitis.
- To evaluate lung function before the heart, abdomen, or lung surgery.
- For smokers
- To evaluate people who are at risk of developing respiratory disease as a result of occupational (work-related) or environmental exposure to harmful substances.
Pulmonary function test procedures are generally safe; however, doctors avoid performing PFTs when a person:
- Is facing a heart problem or has succumbed to a heart attack
- Has recently had an abdominal, heart, or eye surgery
- Is suffering from an aneurysm in the abdomen or chest area
The pulmonary function test procedure is performed usually in an outpatient setting where the person is allowed to go home after the test, or it may be done during a long hospital stay. During the procedure, one may feel dizzy or have breathing difficulty, or have other problems. Common PFTs include:
Spirometry: This is one of the most frequently performed tests. During the test, the individual will be made to sit upright. A clip is inserted into the nose, and a plastic mouthpiece is attached to the spirometry equipment. Next, the individual is instructed to place their lips securely around the mouthpiece and take in as deep a breath as possible before blowing out as hard and fast as they can. It is advised that before the procedure one should avoid smoking or eating heavy meals. Also wearing tight-fitting clothes during the test may affect the test results.
Peak Flow Meter: A peak flow meter measures how fast you can push air out of your lungs when you blow out hard and fast. This is referred to as peak flow rate. Peak flow rate indicates how open the airways are in your lungs. Even before you feel ill, your peak flow may begin to decline. This decline indicates that your asthma may be worsening. Measuring your peak flow can help you determine what caused or "triggered" the drop in the peak flow rate, which medications to add or remove, and when you may require emergency care.
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