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Pulmonary Function Test (PFT)PFTs are noninvasive tests that show how well the lungs are functioning. They also can provide information about airways that may be blocked by mucus. These tests measure lung volume, capacity, rates of flow (how fast and how much air can get in and out of the lungs), and gas exchange.
PFTs are a combination of 2 methods of testing. They are used together and perform different tests. |
Spirometry:
A spirometer is a device with a mouthpiece hooked up to a small electronic machine. A clip will be placed on your nose to keep your nostrils closed. You will take a deep breath and breathe out as hard as you can for several seconds into the tube. It's important that your lips create a seal around the tube, so that no air leaks out. You'll need to do the test at least three times to make sure your results are relatively consistent. If there is too much variation among the three outcomes, you may need to repeat the test again. The highest value among three close test results is used as the final result. Key spirometry measurements include the following:
A spirometer is a device with a mouthpiece hooked up to a small electronic machine. A clip will be placed on your nose to keep your nostrils closed. You will take a deep breath and breathe out as hard as you can for several seconds into the tube. It's important that your lips create a seal around the tube, so that no air leaks out. You'll need to do the test at least three times to make sure your results are relatively consistent. If there is too much variation among the three outcomes, you may need to repeat the test again. The highest value among three close test results is used as the final result. Key spirometry measurements 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.
- Forced expiratory volume (FEV). This is how much air you can force from your lungs in one second.
Plethysmography:
You’ll sit or stand in a small, airtight chamber that is partially or completely see-through and may resemble a phone booth. They’ll put clips on your nose to shut off air to your nostrils. They’ll ask you to breathe against a mouthpiece when it’s both opened and closed. This will provide your doctor with important measurements, including:
Normal values for PFTs vary from person to person. The amount of air inhaled and exhaled in your test results are compared to the average for someone of the same age, height, sex, and race. Results are also compared to any of your previous test results. PFTs help the doctor see lung changes over time and help guide treatment. PFTs can also measure how the airways respond to inhaled medications.
You’ll sit or stand in a small, airtight chamber that is partially or completely see-through and may resemble a phone booth. They’ll put clips on your nose to shut off air to your nostrils. They’ll ask you to breathe against a mouthpiece when it’s both opened and closed. This will provide your doctor with important measurements, including:
- Total Lung Capacity (TLC)
- The amount of air left in your lungs when you breathe out normally, which is called functional residual capacity (FRC)
- How much air is left when you breathe out as much as possible, or residual capacity (RC)
Normal values for PFTs vary from person to person. The amount of air inhaled and exhaled in your test results are compared to the average for someone of the same age, height, sex, and race. Results are also compared to any of your previous test results. PFTs help the doctor see lung changes over time and help guide treatment. PFTs can also measure how the airways respond to inhaled medications.
The entire process usually takes less than 15 minutes. Your doctor will decide the best time to start PFTs. Routine breathing tests may not start until a child is 5 or 6 years old, though some children may be able to do PFTs at an earlier age. "Practice" PFTs can start around age 4. Some at home exercises to help prep for the PFTs are blowing out candles, blowing up/into a balloon, playing with a recorder or whistle. You can also use a PEP device. Always use direct supervision while practicing these techniques.
