What Exams and Tests Diagnose Exercise-Induced Asthma?
If you are having an asthma attack, your health-care professional (whether your primary-care provider or an emergency-department physician) will ask you questions about your symptoms, medical history, and medications. Answer as completely as you can. He or she will also examine you and observe you as you breathe.
He or she will assess the severity of the attack. Attacks are usually classified as mild, moderately severe, or severe. This assessment is based on several factors.
- Symptom severity and duration
- Degree of airway obstruction
- Extent to which the attack is interfering with regular activities
If you have had symptoms and are seeking medical care afterward, the health-care professional will ask questions and perform tests to search for and rule out or exclude other causes of the symptoms. The evaluation will almost certainly include tests of how well you can breathe at rest and may include tests during exertion. These tests are done at rest, after six to eight minutes of exercise, and then at regular intervals until at least 30 minutes after you have stopped exercising. Proper diagnosis is essential to ensure that the most appropriate treatment is given.
Measurements of how well you are breathing can be assessed using the following methods:
- Spirometry: The spirometer is a device that measures how much air you can exhale and how forcefully you can breathe out. The test may be done before and after you inhale a medication. Spirometry is a good way to see how much your breathing is impaired during an attack. This test must be done in the medical office; you may exercise on a treadmill or stationary bicycle. Normally, individuals can blow 70% of their lung capacity out of their lungs in one second. This is referred to as the forced expired volume in one second (FEV1). If airflow is obstructed, this number will be less than 70%. Often lung function in patients with exercise induced asthma is normal.
- Peak flow meter: This is another way of measuring how forcefully you can breathe out during an attack. This device is small and portable and can be used "in the field." This allows testing after six to eight minutes of your usual activity.
- Oximetry: A painless probe, called a pulse oximeter, may be placed on your fingertip to measure the amount of oxygen in your bloodstream.
- Other tests can be used to determine if airways have a tendency to be reactive. These include exhaled nitric oxide measurement and an airway challenge test with methacholine. The methacholine challenge can result in significant asthma symptoms and therefore is done in a facility with the capability of handling potential complications.
No blood test can pinpoint the cause of asthma.
- Your blood may be checked for signs of an infection that might be contributing to the symptoms.
- In severe attacks, it may be necessary to sample blood from an artery to determine exactly how much oxygen and carbon dioxide are present in your bloodstream.
A chest X-ray may also be taken. This is mostly to rule out other conditions that can cause similar symptoms.
In many instances, the history is the most important clue to the diagnosis of exercise-induced asthma. Oftentimes, armed with this information, the health-care professional will empirically trial a medication for exercise-induced asthma. Follow-up visits will then determine if this medication was effective in reducing the symptoms associated with exercise.