Skip to content
My WebMD Sign In, Sign Up

Lung Disease & Respiratory Health Center

Font Size

Lung Function Tests

How It Feels

If you have an arterial blood gas test, you may feel some pain from the needle used to collect the blood. The other lung function tests are usually painless. Some of the tests may be tiring for people who have a lung disease.

You may cough or feel lightheaded after breathing in or out rapidly, but you will be given a chance to rest between tests. You may find it uncomfortable to wear the nose clip. Breathing through the mouthpiece for a long period of time may be uncomfortable.

If you have body plethysmography, you may feel uncomfortable in the airtight plethysmograph booth. But the therapist will be nearby during the test to open the door if you feel too uncomfortable.

If you are given breathing medicine, it may cause you to shake or may increase your heart rate. If you feel any chest pain or discomfort, tell the therapist right away.

Risks

Lung function tests present little or no risk to a healthy person. If you have a serious heart or lung condition, discuss your risks with your doctor.

Results

Lung function tests (also called pulmonary function tests, or PFTs) check how well your lungs work. The normal value ranges for lung function tests will be adjusted for your age, height, sex, and sometimes weight and race. Results are often expressed in terms of a percentage of the expected value. Most test results are available right away.

Normal

Test results are within the normal ranges for a person with healthy lungs.

Abnormal

Test results are outside of the normal range for a person with healthy lungs. This may mean that some kind of lung disease is present. There are two main types of lung disease that can be found with lung function tests: obstructive and restrictive.

Obstructive

In obstructive lung conditions, the airways are narrowed, usually causing an increase in the time it takes to empty the lungs. Obstructive lung disease can be caused by conditions such as emphysema, bronchitis, infection (which produces inflammation), and asthma.

Lung function values in obstructive disease
Lung function test Result as predicted for age, height, sex, weight, or race

Forced vital capacity (FVC)

Normal or lower than predicted value

Forced expiratory volume (FEV1)

Lower

FEV1 divided by FVC

Lower

Forced expiratory flow 25% to 75%

Lower

Peak expiratory flow (PEF)

Lower

Maximum voluntary ventilation (MVV)

Lower

Slow vital capacity (SVC)

Normal or lower

Total lung capacity (TLC) (VT)

Normal or higher

Functional residual capacity (FRC)

Higher

Residual volume (RV)

Higher

Expiratory reserve volume (ERV)

Normal or lower

RV divided by TLC ratio

Higher

FEV1 often increases after using medicine that expands the airways in people with reversible obstructive disease like asthma.

Restrictive

In restrictive lung conditions, there is a loss of lung tissue, a decrease in the lungs' ability to expand, or a decrease in the lungs' ability to transfer oxygen to the blood (or carbon dioxide out of the blood). Restrictive lung disease can be caused by conditions such as scleroderma, pulmonary fibrosis, or sarcoidosis. Other restrictive conditions include some chest injuries, being very overweight (obesity), pregnancy, and loss of lung tissue due to surgery.

Lung function values in restrictive disease
Lung function test Result as predicted for age, height, sex, weight, or race

Forced vital capacity (FVC)

Lower than predicted value

Forced expiratory volume (FEV1)

Normal or lower

FEV1 divided by FVC

Normal or higher

Forced expiratory flow 25% to 75%

Normal or lower

Peak expiratory flow (PEF)

Normal or lower

Maximum voluntary ventilation (MVV)

Normal or lower

Slow vital capacity (SVC)

Lower

Total lung capacity (TLC) (VT)

Lower

Functional residual capacity (FRC)

Normal or lower

Residual volume (RV)

Normal, lower, or higher

Expiratory reserve volume (ERV)

Normal or lower

RV divided by TLC ratio

Normal or higher

WebMD Medical Reference from Healthwise

Last Updated: April 25, 2013
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.

Today on WebMD

Living With Copd
VIDEO
Lung Disease Health Check
HEALTH CHECK
 
Cigarette butts in ashtray
Article
Household Hazards For People With Copd
Article
 

Bronchitis Overview
SLIDESHOW
Copd Myth Fact Quiz
QUIZ
 
Living With Copd
VIDEO
Energy Boosting Foods
SLIDESHOW
 

Pollen counts, treatment tips, and more.

It's nothing to sneeze at.

Loading ...

Sending your email...

This feature is temporarily unavailable. Please try again later.

Thanks!

Now check your email account on your mobile phone to download your new app.

cigarette butts snuffed out in ashtray
SLIDESHOW
Healthy Home Health Check
TOOL
 
Senior woman stretching
Article
Diagnosing Copd
VIDEO
 

WebMD Special Sections