Types of Lung Function Tests
Breathing Tests
Spirometry
Spirometry measures how much air you breathe in and
out and how fast you blow it out. This is measured in two ways: peak expiratory
flow rate (PEFR) and forced expiratory volume in 1 second (FEV1).
PEFR refers to the amount of air you can blow air out as quickly as possible.
FEV1 refers to the amount of air you can blow out in 1 second.
During the test, a technician will ask you to take a
deep breath in and then blow as hard as you can into a tube connected to a
small machine. Your doctor may have you inhale a medicine that helps open your
airways. He or she will want to see whether the medicine changes or improves
the test results.
Spirometry is done to look for diseases and
conditions that affect how much air you can breathe in, such as
sarcoidosis
or lung
tissue scarring. It's also done to look for diseases that affect how fast
you can breathe air out, like
asthma
and
COPD
(chronic obstructive pulmonary disease).
Peak Flow Meter
A peak flow meter is a small, hand-held device that
you blow into. It shows how well air moves out of your lungs. People who have
asthma sometimes use this device. It helps them (and their doctors) check their
breathing. A peak flow meter can be used at home or in a doctor's office.
Lung Volume Measurement
This test measures the size of your lungs and how
much air you can breathe in and out. During the test, you sit inside a glass
booth and breathe into a tube that's hooked to a computer.
Sometimes you breathe in nitrogen or helium gas and
then blow it out. The gas you breathe out is then measured to test how much air
your lungs can hold.
The test can help diagnose lung tissue scarring or a
stiff and/or weak chest wall.
Lung Diffusion Capacity
This test measures how well oxygen passes from your
lungs to your bloodstream. During this test, you breathe in a gas through a
tube. You hold your breath for a brief moment and then blow the gas out.
Abnormal test results may suggest loss of lung
tissue, emphysema (a type of COPD), very bad scarring, or problems with blood
flow through the body's arteries.
Tests To Measure Oxygen Level
Pulse oximetry and arterial blood gas tests show how
much oxygen is in your blood. During pulse oximetry, a small light is placed
over your fingertip, earlobe, or toe to measure the oxygen. This test is
painless and no needles are used.
During an arterial blood gas test, your doctor
inserts a small needle into an artery, usually in your wrist. He or she takes a
sample of blood. The oxygen level of the blood is checked in a lab.
Testing in Infants and Young Children
Spirometry and other measures of lung function
usually can be done in children older than 6 years, if they can follow
directions well. Spirometry may be tried in children as young as 5 years.
However, technicians who have special training with young children may need to
do the testing.
Instead of spirometry, a growing number of medical
centers measure respiratory system resistance. This is another way to test lung
function in young children.
The child wears nose clips and has his or her cheeks
supported with an adult's hands. The child breathes in and out quietly on a
mouthpiece, while the technician measures changes in pressure at the mouth.
During these lung function tests, parents can help comfort their children and
encourage them to cooperate.
Very young children (younger than 2 years) may need
an infant lung function test. This requires special equipment and medical
staff. This type of test is only available at a few centers. The doctor gives
the child medicine to help him or her sleep through the test.
A technician places a mask over your child's nose
and mouth and a vest around your child's chest. The mask and vest are attached
to a lung function machine. The machine gently pushes air into your child's
lungs through the mask. As your child exhales, the vest slightly squeezes his
or her chest. This helps push more air out of the lungs. The exhaled air is
then measured.
In children younger than 5 years, the doctor likely
will use signs and symptoms, medical history, and a physical exam to diagnose
lung problems.
Pulse oximetry and arterial blood gas tests may be
used for children of all ages. |