What is Pulmonary Function Testing?

Pulmonary function testing is used in practice to measure the function of the lungs and diagnose or monitor the progression of respiratory conditions. There are various tests used in practice to provide this information, each of which has a unique procedure and benefits for the patient.

The results are normalized according to the individual characteristics of the patient and abnormal results indicate the need for further investigation as to the cause and suitable treatment options.

Purpose of Testing

Pulmonary function tests are able to provide very useful information about the function of the lungs and respiratory system. They may be requested as a routine check-up, to investigate symptoms related to lung function, to monitor the efficacy of treatment for a lung condition or to assess lung function prior to surgery.

The tests can help in the diagnosis of certain respiratory conditions, such as:

Asthma
Chronic obstructive pulmonary disease (COPD)
Pulmonary fibrosis or scarring of the lung tissue
Bronchitis
Emphysema
Sarcoidosis

Additionally, the tests can help to monitor changes in the lung function or the effect of medication, particularly for individuals that are affected by respiratory conditions.

Types of Tests

There are several different types of pulmonary function tests that may be used to provide information about certain respiratory conditions.

Spirometry is a test that involves the patient breathing as forcefully as possible into a tube that is connected to a machine that measures the volume and flow rate of the air.
Body plethysmography is a test that measures the volume of the air in the lungs when an individual inhales deeply and after exhalation.
Lung diffusion capacity is a test that measures the efficiency of oxygen transfer from the lungs into the blood stream.
Blood oxygen tests such as pulse oximetry and arterial blood gas test are used to measure the concentration of oxygen present in the blood.
Exercise stress test is used to measure the function of the respiratory and cardiovascular system in response to controlled exercise.

Result Measurements

The results obtained from pulmonary function testing are important in the investigation of lung function and the involvement of certain conditions. The values that may be obtained from the tests include:

Peak expiratory flow (PEF)
Forced expiratory volume (FEV)
Forced vital capacity (FVC)
Residual volume (RV)
Expiratory reserve volume (ERV)
Slow vital capacity (SVC)
Total lung capacity (TLC)

The normal values differ according to the specific characteristics of the individual, such as the age, height, weight, gender and ethnicity. As a general rule, values 80% less than normal warrant further investigation and possible treatment.

Patient Advice for the Pulmonary Function Testing

Pulmonary function tests are usually simple and painless, mainly involving measurements of the way the patient breathes. Some individual may find that they feel light-headed or experience shortness of breath during the tests.

It is important that they are advised to refrain from smoking or eating a heavy meal in the 4 to 6 hours prior to performing the test. Additionally, medications that may affect the results of the test, such as bronchodilator medications may need to be ceased for a period before and during the test, depending on the specific case at hand.

Pulmonary function testing is not recommended for patients that have had a recent heart attack or surgery of the eye, chest or abdominal region. Additionally, it may be contraindicated for individuals with a severe respiratory infection or heart disease.

References

http://www.nhlbi.nih.gov/health/health-topics/topics/lft
http://emedicine.medscape.com/article/303239-overview