Pulmonary Function Testing & Preparation
The Pediatric Pulmonary Function Laboratory, part of Hassenfeld Children’s Hospital of New York at NYU Langone, performs a series of breathing tests designed to measure the amount of air in the lungs and how well the lungs can move air in and out.
On testing day, please follow these guidelines:
- Bring a list of all medications your child is currently taking.
- Bring any inhalers, pumps, or medications that your child is using, so we can review them together to ensure you’re using them in the most effective way.
- If your child is not experiencing any symptoms on the day of the test, do not use a bronchodilator, such as Ventolin, ProAir®, Xopenex®, Advair®, Symbicort®, Dulera®, or others, in case your doctor wants to test your child using a bronchodilator.
- Do not let your child drink any caffeinated drinks such as tea, hot chocolate, or soda as they can interfere with testing.
- Avoid having your child eat a large meal because some tests require forceful breathing, which may be difficult with a full stomach.
- Dress your child in loose, comfortable clothing.
Standard pulmonary function tests that we perform include:
Spirometry is the most commonly performed test to assess how well your child’s lungs are functioning. During the test, your child is seated and breathes into a mouthpiece connected to an instrument, known as a spirometer, which is connected to a computer. Each breath is measured and recorded to gauge how much, and how fast, air is going in and out of the lungs.
Often, this test is repeated after giving your child albuterol. The two tests are compared to find out the difference in lung sensitivity so the doctor can adjust your child’s medications accordingly.
Because this test requires only quiet, relaxed breathing, impulse oscillometry is usually given to very young patients or patients who are unable to perform other pulmonary tests. Your child wears a soft nose clip and breathes normally through a disposable, filtered mouthpiece for 20 to 30 seconds as sound waves pulse through his or her airways to help detect resistance. There is a break for a few seconds and then the test repeats several times.
You may hear this test referred to as the “popcorn test” because the sounds waves cause a harmless vibrating sensation on a child's cheeks and in the chest.
Lung Volume Measurements
A computer can measure lung volume in one of two ways. Your child may sit in a body plethysmograph—a transparent acrylic booth that is similar to a telephone booth—and breathe into the same tube used for spirometry for approximately 60 seconds with the door to the booth closed. Another method to help determine lung capacity is called a nitrogen washout, which requires your child to inhale 100 percent oxygen before each exhale, for two to five minutes while the door to the booth remains open.
Respiratory Muscle Testing
Respiratory muscle testing measures the strength of the muscles used for inhaling and exhaling during both normal and forced breathing. Respiratory muscle testing can be helpful in assessing lung conditions in children who have muscle weakness that may be caused by damage to the nerve leading to the diaphragm or paralysis from a spinal cord injury, muscular dystrophy, or other condition.
Lung Diffusion Testing
Sometimes called a DLCO, a lung diffusion test measures how well gases such as oxygen and carbon dioxide move between the air in the lungs and the blood flowing into the lungs. It may help your doctor to diagnose other lung problems such as bleeding in the lungs, or to determine if there is lung damage from factors such as radiation or chemotherapy.
Exercise Challenge Test
An exercise challenge test is often performed on athletic teenagers who do not have asthma, but feel that poor breathing is impairing their ability to play sports. The test starts with a basic spirometry test to assess your child’s resting lung function. Then the teenager engages in some form of exercise, such as riding a bicycle, to increase his or her heart rate for four to six minutes, or until symptoms appear.
A spirometry test is repeated every five minutes, for a total of five times, to see how the exercise affects his or her lung function. If she or he has difficulty breathing, the bronchodilator medicine albuterol is administered to determine if it helps control the symptoms. Another spirometry test is then performed to confirm that your child’s lung function has returned to normal and that the symptoms have subsided.
This test is more time consuming than the others, taking an average of 60 to 90 minutes, and is done only on the second and last Monday of the month.
A sweat test can be performed on any baby who failed the screening test for cystic fibrosis, which is mandatory for newborns in New York State. A sweat test simply measures the amount of salt in your baby’s sweat—high levels indicate cystic fibrosis—and can be done on infants as young as six weeks old. Tests are by appointment only, and the results are available within 24 to 48 hours.