Bronchial challenge testing (BCT) DIRECT

Question 1

What is bronchial challenge testing?

Answer 1

Diagnostic test used to assist in diagnosis of asthma

• Stimulus is administered to airways as aerosol or powder
• May provokes bronchoconstriction in asthma/BHR

•Dose/Response relationship:
oProvocative Dose (PD)
oProvocative Concentration (PC)

Question 2

What is bronchial hyper-responsiveness?

Answer 2

• Excessive bronchial narrowing that manifests itself as an exaggerated bronchoconstrictor response of the airways to various inhaled stimuli
• Most patients with asthma and COPD show enhanced sensitivity

Question 3

Give ways in which the bronchial challenge can be done directly and indirectly:

Answer 3

Direct
-Histamine, Methacholine
Indirect
-Exercise, EVH, Hypertonic Saline, AMP, Mannitol

Question 4

Give examples of indications for BCT (bronchial challenge testing):

Answer 4

•To identify or exclude a diagnosis of bronchial hyperreactivity or asthma:
oSymptoms (e.g. cough, wheeze etc.)
oNormal lung function

• To evaluate occupational asthma
• To assess severity of bronchial hyperresponsiveness

Question 5

Are the contraindications used for BCT the same as PFT’S?

Answer 5

yes

Question 6

Give examples of contraindications of BCT:

Answer 6

•Airflow Obstruction:
oFEV1 < 60% predicted (adults/children)
o or < 1.5 litre (adults)
o Possible large ↓ in FEV1

-Same as spirometry
•Pregnancy/breast feeding
•Recent RTI (6 weeks)

Question 7

What should the patients do prior to the test?

Answer 7

Patient should refrain from smoking, 1 hour before testing

• Discontinue caffeine on the day of testing
• Check patients medication use, have been withhold the right amount of time prior to testing

Question 8

What is the common range of concentration used (mg/ml)?

Answer 8

0-16mg/ml

Question 9

When is the test end point for BCT?

Answer 9

A fall of ≥ 20% in FEV1 from baseline (PC20/PD20)

Question 10

Why is histamine/metacholine a direct BCT?

Answer 10

Histamine/Methacholine act directly on bronchial smooth muscle
•Can cause bronchoconstriction in patients with asthma/↑BHR at a lower dose

Question 11

How would you categorise PC20?

Answer 11

>

16. Normal bronchial responsiveness

4 - 16. Borderline BHR

1. 0 – 4.0. Mild BHR (positive test)
2. 25 – 1.0 Moderate BHR

< 0.25- Marked BHR

Question 12

WHICH NEUROTRANSMITTER DOES METACHOLINE MIMMICK?

Answer 12

ACETYLCHOLINE