What are lung function tests?
Lung function tests, also known as pulmonary function tests (PFTs), are a group of different kinds of breathing tests that measure how well your lungs work. These tests look at how much air you can breathe in and out, how well your lungs transfer oxygen to the blood, and how strong your breathing muscles are, as well as diagnosing or monitoring lung disease.
Your results will help determine whether your lung function is within a normal range by comparing it to what's normal for someone your age, sex, and height. In Singapore, this test is available at public or private hospitals, polyclinics, and respiratory specialist clinics.
What are lung function tests used for?
Lung function testing is usually done by your healthcare provider to help diagnose, monitor, and manage a range of lung conditions. These tests are useful for:
Diagnosing and assessing chronic lung diseases such as asthma, chronic obstructive pulmonary disease (COPD), pulmonary fibrosis, and chronic bronchitis
Monitoring lung disease to track its progression
Assessing whether there's airway narrowing or obstruction in the lungs
Assessing lung function before surgery or certain medical procedures
Deciding on treatment options and measuring response to treatment
Assessing lung damage caused by exposure to chemicals, pollutants, or other harmful substances
Why do I need a lung function test?
Your healthcare provider may recommend a lung function test if you:
Have symptoms of lung disease, such as shortness of breath, wheezing, coughing, or chest tightness
Have been exposed to substances that can harm your lungs, such as cigarette smoke, air pollution, chemicals, or dust
Have a chronic cough or difficulty breathing
Experiencing chest tightness or pain when breathing
Have abnormal chest X-ray results that suggest lung disease
Even if you don't have symptoms, your healthcare provider may order a lung function test as part of a routine physical examination, especially if you have a family history of lung disease.
If you are experiencing any of the mentioned symptoms, request an appointment with Thomson Medical. Our specialists can assist with further diagnosis, including a lung function test, to determine the underlying cause of your symptoms and provide a tailored treatment plan.
Will I need to do anything to prepare for the tests?
A lung function test is not a complicated test. You'll usually be asked to breathe in and out with full effort or perform activities such as walking or using a stationary bicycle or treadmill while being monitored.
However, to get accurate results from these tests, you need to do some preparation beforehand, which includes:
Avoid smoking for at least 6 hours before the test
Avoid drinking alcohol for at least 8 hours before the test
Avoid eating large meals at least 2 hours before the test (as a full stomach can restrict lung expansion)
Avoid any heavy exercise before the test
Wear loose, comfortable clothing that does not restrict your breathing or movement
Avoid caffeine
If you use an inhaler, ask your doctor if you should stop using it before the test
You may also need to stop taking some of your regular medicines before the test, as certain medicines can affect the results. Talk to your doctor about when to stop taking each medication to ensure it's safe.
Always follow any additional directions from your healthcare provider about medications, what to wear and eat, or any activity restrictions before your lung function test.
What to expect during the lung function test?
Once the preparation is complete, the lung function test will begin. There are several types of lung function tests, most of which involve breathing through a spirometer. This instrument measures how much air you can breathe in and out and how quickly you can exhale.
Depending on which tests are performed, the total duration can be between 20 and 60 minutes. Your healthcare provider will provide specific instructions for each test during the assessment. Here are some common lung function tests that can be performed, which include:
Spirometry test
A spirometry test is the most common lung function test and measures your lung size, capacity, and airflow rate. Here's what to expect during the test:
You'll sit in a chair, and your healthcare provider will place a soft clip on your nose to make sure you breathe only through your mouth.
You'll then be given a mouthpiece connected to a spirometer.
Then, put your lips on the mouthpiece, inhale deeply, and blow as hard and fast as you can.
The spirometer will measure how much air you blow and how fast you blow it out.
To help open your airways, you may be given a medicine. Then you'll blow into the tube again to see if the medicine helps you blow out more air faster.
Lung volume test
A lung volume test, also known as body plethysmography, is a test that measures how much air your lungs can hold and how much air remains in your lungs after you exhale. The procedure is as follows:
You'll be in a small, airtight room with clear walls that looks like a telephone box.
You'll wear a soft clip on your nose to make sure you only breathe through your mouth.
You'll put your lips tightly around a mouthpiece.
The changes in air pressure in the room show how much air your lungs can hold, as well as how much air is left in your lungs after you exhale.
Let your healthcare provider know if you feel uneasy in small spaces (claustrophobia), so they can help you feel more at ease during the test.
Gas diffusion test
During this test, you'll be asked to inhale a small, safe amount of carbon monoxide mixed with other harmless gases. Carbon monoxide is used because it binds strongly to haemoglobin and helps measure how well oxygen moves from the lungs to the blood. The procedure is as follows:
You’ll sit in a chair with a soft clip on your nose to make sure you only breathe through your mouth.
You’ll place your lips tightly around a mouthpiece that’s connected to a spirometer.
You’ll be instructed to breathe out fully, then take a deep breath in to fill your lungs with the test gas.
You’ll then hold your breath for about 10 seconds.
After holding your breath, you’ll exhale completely. The spirometer will measure how much carbon monoxide you exhaled compared to what you inhaled.
The change in concentration of the gases will be used to evaluate how well oxygen is transferred into the bloodstream.
Six minute walk test
During this exercise test, your healthcare provider will evaluate your tolerance and how your lungs respond to physical activity. Here’s what to expect during the test:
Your blood pressure, heart rate, and oxygen levels are checked before the test.
You will then walk back and forth for six minutes, covering as much distance as possible.
Your heart rate and the amount of oxygen in your blood will be checked as you walk.
After six minutes, your blood pressure will be measured again, and you'll rate your shortness of breath and fatigue.
You’ll be asked to rate your breathlessness and fatigue before and after walking.
Cardiopulmonary exercise test (CPET)
During this test, your healthcare provider will measure how your heart, lungs, and muscles work together during exercise. The procedure is as follows:
Before the test, your healthcare provider will attach a sensor to your body that measures your heart rate, blood pressure, and blood oxygen levels.
You'll also be given a face mask or mouthpiece to breathe through, which measures how much oxygen you breathe in and how much carbon dioxide you breathe out.
After that, you’ll be instructed to walk on a treadmill or ride a stationary bicycle for a total of 10 to 20 minutes.
You’ll exercise starting easy and gradually increasing intensity.
The test continues until you reach your limit, then you’ll cool down at an easier pace.
You’ll be asked how you feel throughout the test, and you can take breaks if needed.
Once the test is complete, you can return to your normal activities right away, including exercise, unless instructed otherwise.
If you would like more information about lung function tests, request an appointment with Thomson Medical. Our specialists can help explain this procedure to you in more detail and determine which test best suits your medical condition.
What do the results mean?
During a lung function test, your doctor will assess how well your lungs are working by looking at several key measurements:
Forced Expiratory Volume (FEV1), which measures the amount of air you can forcefully exhale in one second.
Forced Vital Capacity (FVC), which is the total amount of air you can exhale after taking a deep breath.
The FEV1/FVC ratio compares how much air you exhale in the first second to the total amount exhaled. This ratio helps to diagnose obstructive lung diseases such as asthma and COPD.
Peak Expiratory Flow (PEF), which is the fastest speed at which you can exhale.
Interpreting your results
If your key measurements are within the normal range, this suggests that your lung function is as expected for someone your age, sex, height, and weight.
Conversely, abnormal results may indicate a lung condition. However, a lung function test alone cannot diagnose a specific lung disease. Instead, they help your healthcare provider determine whether the issue is restrictive or obstructive.
An obstructive lung condition causes your airways to narrow, making it difficult for air to leave your lungs. Examples of obstructive conditions include asthma and bronchitis.
A restrictive lung condition decreases the amount of air that your lungs can hold. This may happen if your lungs or chest muscles cannot expand fully when you breathe in, as can occur with pulmonary fibrosis and interstitial lung diseases.
Lung function test cost in Singapore
In Singapore, a lung function test is available at public or private hospitals, polyclinics or a respiratory specialist's clinic. The cost of the test varies depending on whether it is done as a stand-alone test or as part of a health screening package and the healthcare facility chosen.
In general, the cost of the test is between SGD 115 and 350 in a private hospital. However, the cost may be lower if the test is done in a public hospital or if you only need a specific lung function test (such as spirometry).
To help cover the cost, you can use up to SGD 300 per year from your MediSave account if the lung function test is considered an outpatient diagnostic test for a medical condition. However, MediSave does not cover tests that are performed purely as part of a general health screening without a medical indication.
In addition, if your lung function test is part of the management of an approved chronic condition, such as asthma or COPD, under the Chronic Disease Management Program (CDMP), you may be able to use MediSave to pay for the test (up to $500 or $700 per year, depending on the complexity of your condition).
Always check with your clinic to see if your specific test is eligible for MediSave, as eligibility may depend on your diagnosis and clinic choices. If you have private insurance, check with your provider to see if a lung function test is covered under your policy.
For detailed fee information and payment options, request an appointment with our specialists at Thomson Medical today.
Are there any risks to the tests?
A lung function test is generally a safe procedure, but you may experience some mild discomfort. However, these symptoms should disappear shortly after the test. Here's what you may experience:
Shortness of breath
Dizziness
Coughing from blowing hard into the mouthpiece
Fatigue from the exercise test
Feeling uncomfortable in small spaces (claustrophobia), especially if the test is done in an airtight booth
However, the following conditions typically prevent the need for lung function tests:
Had a recent heart attack or stroke (within the past three months)
Certain heart conditions
A large aneurysm of a major blood vessel
A major head injury
Recent eye surgery
Always let your healthcare provider know about your medical history before the test so they can ensure it’s safe for you.
FAQ
What does it mean if my lung function test is abnormal?
Abnormal results may suggest you have a lung condition. This could be:
Obstructive lung disease (like asthma or COPD), where your airways are narrowed, making it hard to exhale fully.
Restrictive lung disease (like pulmonary fibrosis), where your lungs are stiff or can’t fully expand, reducing lung volume.
How can I tell if I have poor lung function?
Common signs of poor lung function include:
Shortness of breath, even with mild activity
Wheezing or chest tightness
Persistent cough
Frequent chest infections
Feeling tired or weak
Difficulty taking deep breaths
How can I improve my lung function?
To improve lung function, there are several tips you can try, such as:
Quit smoking to prevent further lung damage
Exercise regularly (walking, swimming, cycling) to strengthen your lungs
Practice breathing exercises like diaphragmatic or pursed-lip breathing
Stay hydrated to help keep mucus thin and easier to clear
Avoid air pollutants such as smoke, dust, and strong chemicals.
Eat a healthy diet rich in antioxidants, such as fruits or vegetables
Use a humidifier to keep airways moist.
Take prescribed medications or inhalers if you have a lung condition.
What is a good result from a lung function test?
A good result means your lung function is within the expected range based on age, sex, height, and weight. Some key spirometry values are:
FEV1 (Forced Expiratory Volume in 1 second):
It measures how much air you can breathe out in one second. 80% or more of the predicted value is considered normal.
FVC (Forced Vital Capacity):
It measures the total amount of air you can breathe out forcefully. A high FVC means you have a large lung capacity.
FEV1/FVC Ratio:
A normal ratio is over 70%. If it's lower, it may indicate obstructive lung disease such as asthma or COPD.
Can a GP do a lung function test?
Yes, some general practitioners (GPs) in Singapore can perform basic lung function tests like spirometry in their clinics. For more detailed tests, you may be referred to a hospital or a specialised lung function clinic.
The information provided is intended for general guidance only and should not be considered medical advice. For personalised recommendations and tailored advice, please consult a specialist at Thomson Medical. Request an appointment with Thomson Medical today.
For more information, contact us:
Thomson Specialists Paragon (Health Screening)
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Call: 6735 0300
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