Provocative bronchial challenge test


Capnographic monitoring of inhalative challenge provides a continuous and dynamic view of bronchial response to any broncho-constrictive agent. Non-specific (acetylcholine, carbamylcholine etc...) and specific (allergens) reactivities can be measured without the disturbances caused by forced expiration.

Example of Carbamylcholine provocation test in an asthmatic patient : Inhalation of cumulative doses of cch ; ventilatory assessment using both capnographic monitoring and iterative PEF measurements.

Waveform samples
of main stages
of recording
.

a time

b

c

d

e

f

g

a

b

c

d

e

f

g

Trends of S1 and S2 during a carbamylcholine challenge test

Inhaled doses (red numeric marks 1-12)
Red marks (above time axis) allow main incidents noted by the physician during recording to be located : drug administration, PEF measurement, clinical observations etc...

Chart interpreting above graph

1 PEF=450

4 320 mcg cch

7 PEF=200

10 PEF=300

2 80 mcg carbamylcholine

5 640 mcg cch

8 PEF=200

11 Pirbuterol ( 2 puffs)

3 160 mcg cch

6 1280 mcg cch, PEF=300

9 Pirbuterol (3 puffs)

12 PEF=390

Capnographic waveforms (red alphabetic marks a-g)
Main stages of recording are identified using alphabetic marks which allow corresponding capnographic samples to be located (above trend curves).

Trends
After a few minutes of reference recording (mark a, S2=0.3, PEF=450l/min) which confirms the absence of bronchospasm, cumulative doses of carbamylcholine are inhaled every 2 minutes (marks 2-6). Distinct deterioration of indices S1 and S2 appears as early as inhalation of a cumulated dose of 320 mcg (mark 4). Further doses (marks 5-6) result in severe bronchospasm (waveforms d-e) associated with a dramatic increase of S2 (0.9) and reduction in PEF (200 l/min). The situation slowly improves (waveforms f-g) after nebulization of a beta mimetic therapy (marks 9 et 11).

Interpretation
This test proves marked bronchial hyperresponsiveness assessed by capnographic monitoring as well by spirometric measurements.

 

Other carbamylcholine bronchial challenge including complete scrolling waveform (requires a "frame compatible" navigator)