Pulmonary function test (PFT) is an investigation into the various functions of the lungs. This examination aims to assess why certain lung functions are disrupted. Various tests can be performed.
Examination of the pulmonary function is done if the lung function is impaired. An impaired lung function may be shown as chest tightness and coughing. Diseases which may disrupt the lung function and which may be identified with pulmonary function tests are, for example, asthma and chronic obstructive pulmonary disease (COPD).
With the aid of pulmonary function equipment, the volume of the lungs and the degree of any airway narrowing is measured. During the examination, the patient breaths through a mouthpiece into the pulmonary function device, while the nose is kept closed by means of a clamp.
There are several tests that belong to the pulmonary function test. The choice of doing a specific test is depending on the symptoms.
- Spirometry. During a spirometry, the lung capacity is determined. This requires that the patient should breathe several times maximally into a spirometer.
- Diffusion test. A diffusion test measures the speed at which inhaled oxygen is delivered to the blood. This requires that the patient should take a deep breath and hold breath for ten seconds. Then the patient will blow it back out into the device.
- Plethysmography. This study takes place in an enclosed space (bodybox) and measures the resistance of the airway. This way is determined how much effort it takes to breathe. In addition, the total lung capacity is measured.
- Shunt. There may also some blood be taken in order to determine oxygen and carbon dioxide levels in the blood vessels. This can be done after the patient has inhaled one hundred percent oxygen for thirty minutes.
- Compliance study. With a compliance study, the elasticity of the lungs is measured. A thin tube is inserted through the nose into the esophagus, after which the patient takes some deep breaths.
- Histamine provocation test. Here, the sensitivity of the airway is determined. The patient inhales a small amount of histamine. As a result, he or she can start coughing or sneezing.
- Exercise stress test. During an exercise stress test, the functioning of the lungs is examined during effort. While the patient is cycling on a home trainer, the amount of oxygen in the blood and the heart rate and breathing is checked. The physical load is continuously increased until the patient has reached his or her maximum.
- Pulmonary muscle strength test. A pulmonary muscle strength test determines the maximum strength of the respiratory muscles. This requires the patient to inhale and exhale maximally against a closed valve.
Sometimes, the tests are repeated after administration of a bronchodilator medicine. Pulmonary function test takes about thirty minutes to two hours.