In recent years bronchial provocation tests have been developed in an attempt to enable clinicians to identify asthma more accurately. These tests have been limited in their use to pulmonary function laboratories because many require specialized equipment or specially trained staff. There are two broad categories of bronchial provocation test, “direct” and “indirect” challenge tests.
Direct challenge tests use pharmacological agents such as histamine or methacholine that act on specific receptors on the bronchial smooth muscle causing it to contract. Indirect challenge tests such as exercise, eucapnic hyperpnea (EVH), adenosine monophosphate (AMP), hypertonic saline or inhaled mannitol (which is what we use in our Lab) work by triggering the release of inflammatory mediators that in turn cause bronchial smooth muscle to contract in sensitive individuals.
We recently enjoyed a visit from Stuart Jack (pictured), the Territory Manager for CareFusion Australia & New Zealand who demonstrated the eucapnic hyperpnea (EVH) kit. EVH is regarded as the “gold standard” challenge to identify exercise-induced asthma particularly in elite athletes. It was developed because clinicians could not be certain that subjects undergoing standard exercise testing were exercising at a sufficiently high intensity to provoke exercise induced asthma. EVH involves the inhalation of dry air with added CO2 (5% CO2 21% O2 74% N2) for 6 minutes at a target ventilation rate based on the subjects FEV1.
Thanks Stuart for a very entertaining and informative visit.
Vanessa
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