Asthma is a disease that involves inflammation of the airways. It leads to symptoms like difficulty breathing, coughing and wheezing. Pulmonary function tests are used in the diagnosis and monitoring of asthma. Some of these tests involve breath tests. "Positive Options for Children with Asthma: Everything Parents Need to Know" by O.P. Jaggi suggests that in asthma, breath tests are used to measure lung capacity and involve breathing into devices.
Spirometry
Spirometry is a type of pulmonary function test that measures how much air moves into and out of the lungs, according to National Jewish Health. It also measures the rate--length of time--at which this happens. During a spirometry test, a patient is asked to blow into a spirometer. The patient has to blow as hard and as fast as he can. The spirometer then measures the amount of air the patient blew in the first second and the total amount of air blown out by the patient. These measurements are used to diagnose lung diseases, including asthma. This test is also used to monitor asthma therapy and to determine the severity of an asthma attack.
Methacholine Challenge
"The American Medical Association Essential Guide to Asthma" by American Medical Association says that methacholine is a substance that causes airway constriction only in asthmatic patients. Before this challenge, a spirometry test is performed to gauge a patients ability to breath effectively. During a methacholine challenge, a patient is asked to breathe in a small amount of methacholine. After this, the patient goes through another spirometry test. The spirometry test is used to determine if a patients ability to breathe decreases due to methacholine inhalation. This test can be used to determine if a patient has asthma.
Peak Flow Monitoring
A peak flow meter is a small, portable device that is used to measure how narrow the airways are. According to the American Academy of Allergy, Asthma and Immunology, they are used to find out how severe an asthma attack is; check a patient's response to treatment during an asthma attack; and to check for worsening lung function. During this breath test, an asthmatic patient breathes forcefully into a peak flow meter. The scale on the peak flow meter is used to measure the rate at which the patient exhales.
This test is done three times and the highest measurement is considered a patient's best reading. Subsequently, other measurements are compared to this value. During an asthma attack, this test shows a reduction in the force of expiration due to narrowing of the airways.
References
- MayoClinic: Asthma - Tests and diagnosis
- "Positive Options for Children with Asthma: Everything Parents Need to Know"; O. P. Jaggi; 2005
- National Jewish Health: Spirometry
- "The American Medical Association Essential Guide to Asthma"; American Medical Association, AMA; 200
- American Academy of Allergy, Asthma & Immunology: Tips to Remember: Peak Flow Meter
