Methacholine Challenge Test
The methacholine challenge is a lung-health test used to diagnose asthma in people presenting symptoms. It is one of several bronchial provocation tests, which have been developed as diagnostic tools for respiratory conditions. The patient inhales small dosages of methacholine, which is a drug that simulates the airway constrictions of asthma. A significant decline in lung function, as measured by a spirometer, may point to a diagnosis of asthma. A similar test can be performed with histamines.
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Why Would I Receive a Methacholine Challenge?
A methacholine challenge can be administered for a variety of reasons. One common reason is diagnostic: a physician has documented your asthma-like symptoms but wants additional information before confirming the diagnosis. Asthmatic symptoms might include:
- coughing fits,
- shortness of breath,
- chest tightness,
- wheezing, and
- lack of sleep from nighttime respiratory discomfort.
You might also have reason to repeat the challenge. Following diagnosis, your physician may want to measure the efficacy of your asthma medications. Data from a methacholine challenge can allow him or her make adjustments in your treatment that help you cope with your condition.
How Will a Methacholine Challenge Help My Condition?
A methacholine challenge can provide your physician with the information he or she needs to formulate a diagnosis for the symptoms you’re experiencing. You’ll have more and better treatment options if asthma can be identified. A challenge can also document your condition’s progress, enabling your caregivers to revise medications and step up treatment.
What Should I Expect from a Methacholine Challenge?
If you’re scheduled for a methacholine challenge, there are several things you can do beforehand to enhance the testing experience:
- Follow your physician’s directions with regard to any drugs that you’re taking. Respiratory, pain, and other types of medications can skew test results.
- Avoid large meals and caffeinated beverages before a methacholine challenge. A full stomach can impede proper breathing; caffeine artificially opens airways.
- Don’t exercise strenuously beforehand.
- Wear loose-fitting garments with a minimum of jewelry.
Methacholine challenges are typically conducted in a doctor’s office or in the pulmonary function lab of a hospital. Your physician or a pulmonary function technologist will oversee the test. A challenge typically follows these steps:
- A baseline spirometry test, to provide comparative data for analysis.
- Inhalation of a saline (saltwater) solution followed by another spirometry test.
- Several episodes of methacholine inhalation, followed each time by a spirometry test. The methacholine dosage will increase slightly with each additional inhalation.
- Completion of the test when you experience a drop in lung function of 20 percent or more, as measured by the volume of air you can breathe out in one second (medically designated as “FEV1”). You will receive a bronchodilator to reverse constriction, and then wait on site until your breathing has returned to pre-test levels.
The purpose of the challenge is to find the point at which your lung function declines, due to artificially induced bronchoconstriction. The methacholine dosage required to reach that point is the test result. It is also possible that no drop in lung function will occur. In those cases, no more than five to ten dosages will be administered.
What Are the Possible Side Effects?
Methacholine challenges are generally safe and low risk. There is some chance that you’ll experience:
- Chest tightness
- Shortness of breath.
Because methacholine is used to constrict the bronchial passages, it does, in rare cases, lead to a more pronounced asthma event. The medical personnel administering your test will know before you do whether an attack is imminent. If this happens, they will give you a bronchodilator to reverse the procedure, cutting short the asthmatic response.
Persons with unstable heart conditions, unchecked high blood pressure, or an aneurysm may not be good candidates for a methacholine challenge.
What Is My Prognosis with a Methacholine Challenge?
A methacholine challenge is a diagnostic tool for identifying asthma. Having good medical data will assist your physician in making appropriate determinations about your care, which is a key to managing your condition and improving long-term outlook.
When It Comes to Respiratory Health, We’re a Breath of Fresh Air
If you’re dealing with a respiratory ailment or condition, see your Baptist Health physician. He or she will be able to assess your condition and determine which medical treatments, if any, are most appropriate for you.
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