Bronchial provocation Testsor

Bronchial challenge Test

Attaran D,Pulmonologist , Associate professor Mashhad university of medical sciences

Provocation TestTo assess bronchial hyperresponsiveness

(BHR)

Most clinically useful when the diagnosis of asthma not clear-cut

contAsthma characterized by airway

inflammation, BHR and reversible obstruction

Diagnosis of asthma is most often made with symptoms and airway obstruction

While BHR is a key feature of asthma , provocation

tests are not necessary to establish the diagnosis

Indications Atypical features of asthma

Asthma symptoms with NL SpirometryFailure to asthma therapyPersistent cough

IndicationsEvaluation possibility of occupational asthma

Excluding a diagnosis of asthma in high risk occupations

Monitoring asthma therapy ( BHR & inflammation)

contraindicationAbsolute Severe airflow limitation (FEV1 < 50%)

Acute coronary syn or stroke

Severe HTN

Cerebral or aortic aneurysm

contraindicutionRelative Moderate obstruction (FEV1 <60%)

pregnancy

Cholinesterase inhibitor medication

Recent upper or lower respiratory infection

Categories of Tests

Direct test (Methacholine –Histamines) Direct effect on smooth muscles

Indirect test (Exercise- cold air ) Release of cytokines

Methacholine testMost widely used method to assess BHR

Cholinergic effect

Sensitive test for diagnosis of asthma >90%

False positive (COPD – CF – smoky – recent infection)

contThe test consists of performing spirometry at

baseline and after each dose of nebulized

methacholine

Povocation concentration that results in 20% reduction in FEV1 (PC 20 ) is determined.

The effect of increasing the inhaled dose of histamine or methacholine in a healthy subject (red) and an asthmatic patient (blue). The provocative concentration is the amount of inhaled agonist required to drop the FEV1 by 20 percent from the baseline (PC20 FEV1), and is much less in the asthmatic than in the normal subject (0.8 versus 20 mg/mL). An increase in responsiveness is characterized by a decrease in the PC20.

Respiration. 2005 Sep-Oct;72(5):523-8.

Airway hyperresponsiveness to methacholine in chemical warfare victims.

Mirsadraee M, Attaran D, Boskabady MH, Towhidi M. Department of Pulmonary Medicine, Islamic Azad University of Mashhad, Iran. Abstract BACKGROUND: The lung is one of the most exposable organs to chemical warfare agents such

as sulfur mustard gas. Pulmonary complications as a result of this gas range from severe bronchial stenosis to mild or no symptoms. Airway hyperresponsiveness (AHR) which is usually assessed as response to inhaled methacholine is the most characteristic feature of asthma. AHR is reported in chronic obstructive pulmonary disease patients and smokers, and may also show in chemical warfare victims. However, there are little reports regarding AHR in chemical warfare victims.

OBJECTIVE: Therefore, in this study, airway responsiveness to methacholine in victims of chemical warfare was examined.

METHODS: The threshold concentrations of inhaled methacholine required for a 20% change in forced expiratory flow in 1 s (FEV1; PC20) or a 35% change in specific airway conductance (PC35) were measured in 15 chemical war victims and 15 normal control subjects.

RESULTS: In 10 out of 15 chemical warfare victims (two thirds), PC20 and PC35 methacholine could be measured and subjects were called responders. AHR to methacholine in responder chemical war victims (PC20 = 0.41 and PC35 = 0.82 g/l) was significantly lower than in normal subjects (PC20 = 5.69 and PC35 = 4.60 g/l, p < 0.001 for both cases). There was a significant correlation between FEV1 and PC20 methacholine (r = 0.688, p < 0.001). The correlations between PC20 and PC35 were statistically significant as well (r = 0.856, p < 0.001).

CONCLUSION: Results showed increased airway responsiveness of most chemical warfare victims to methacholine which correlated with the FEV1 value and which may be related to chronic airway inflammation or irreversible airway changes.