Methacholine Challenge Protocol

A methacholine challenge test is a diagnostic tool used to assess airway responsiveness. During the test, a constriction of the airways is triggered and measured. The results are then reviewed to determine whether or not you have asthma.

Indications

• A methacholine challenge test is often ordered by your physician if you have been exhibiting symptoms of asthma or already have asthma. Symptoms may include chest tightening, cough or wheezing.

Procedure

• During a methacholine challenge you will inhale increasing amounts of methacholine. Various parameters of lung function are measured before and after each inhalation. The findings are reported as a percent reduction in forced expiratory volume, or FEV1. After a response has been triggered, you will then be given a bronchodilator to relax the airways. The test should always be performed in a setting where emergency personnel can quickly respond if necessary.

Contraindications

• According to Chest, the Journal of the American College of Chest Physicians, if you have an already reduced lung volume or poorly controlled blood pressure, you should not participate in the test. Additionally, if you are pregnant, breastfeeding or have had a recent respiratory infection, you should not participate. Since technique is key, you should be able to follow directions and perform the maneuvers properly.