lung disease , there is a decrease in the air flow caused by a narrowing or blockage of the airways such as with asthma , emphysema , and chronic bronchitis . In restrictive lung disease, there is a decrease in the amount of air that is inhaled, because there is a decrease in elasticity or amount of the lung tissue. Learn to make informed health care decisions with the Medical Encyclopedia at drkoop.com.">

Lung function

How the Test is Performed:
There are 6 lung function tests that can be done at home.
Match Test: Light a match and hold it 6 inches from your mouth. Take a deep breath, then with your mouth open, try to blow out the match with a forceful exhalation. Do not pucker your lips to increase the force of the air flow. This checks the force of the exhalation (breathing out).

Forced expiratory time (FET): Breathe in as deeply as possible. With your mouth open, exhale as fast and completely as possible. Use a watch to time the number of seconds it takes for you to exhale the air. Repeat this 3 times and record the fastest time.

Peak expiratory flow rate (PEFR): This test requires a peak expiratory flow monitor. Breathe in as deeply as possible. Blow into the instrument's mouthpiece as hard and fast as possible. Do this 3 times, and record the highest flow rate.

Forced vital capacity (FVC) and forced expiratory volume in one second (FEV): This test requires a hand-held spirometer. Breathe in as deeply as possible, then blow out into the mouthpiece of the instrument as fast, hard, and long as possible. Expel all of the air in your lungs. Repeat it 3 times and record the highest numbers.

Maximum ventilatory volume (MVV): This test requires a spirometer. Blow as hard and fast as possible into the mouthpiece with repeated rapid in and out breaths for exactly 15 seconds. Multiply the recorded number by 4 to determine the value for 1 minute.

How to Prepare:
Loosen any tight clothing that might restrict your breathing. Sit up straight or stand while performing the tests.

Infants and children:
The physical and psychological preparation you can provide for this or any test or procedure depends on your child's age, interests, previous experience, and level of trust. For specific information regarding how you can prepare your child, see the following topics as they correspond to your child's age:



How it Feels:
There is usually no discomfort.

Risks:
There are no significant risks.

Why this Test is Performed:
Home testing may be useful in monitoring the progress of a disease such as asthma , emphysema , or chronic bronchitis . It can assess the effectiveness of various treatments. It is a way to screen for some lung diseases . An improvement in lung function can be measured if one is starting an exercise program or has stopped smoking .

Normal Values:

  • match test: You are able to blow out the match without difficulty.
  • FET test: You can expel the air after a deep breath in 2 to 5 seconds.
  • PEFR test: The normal values vary with a person's age, sex, and size. Generally, if the PEFR is 80% or more of the predicted normal value, it is acceptable.
  • FVC and FEV tests: Normal values vary with age, sex and size. Tables are provided with the spirometers.
  • MVV test: This varies with age, sex, and size. Normal values are usually 15 to 20 times the FVC.



Abnormal Results:
If the tests are not in the normal ranges, then consult a health care provider.

Cost:
Information not available.

Special Considerations:
The accuracy of these tests depend on taking full, deep breaths and blowing the air out through the mouth. While these tests may be useful in screening some lung diseases , they are not sensitive enough to show early damage from smoking . Smokers should not be reassured by normal results.


This is an illustration of the major features of the lungs and bronchial tree. The inset is of the alveoli. They are the microscopic blood vessel-lined sacks in which oxygen and carbon dioxide gas are exchanged.



Spirometry is a painless study of air volume and flow rate within the lungs. Spirometry is frequently used to evaluate lung function in people with obstructive or restrictive lung diseases (such as asthma or cystic fibrosis).