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Clinical Perspectives
ATS Publishes Recommendations:
Bronchial Provocation
Testing
by Susan Blonshine, BS, RRT, RPFT, FAARC
B
ronchial provocation
testing is widely performed in the
evaluation of airway hyperresponsiveness. Several methods
have been described in the literature, but the most commonly
used nonspecific agent is
aerosolized methacholine.1 Exercise-induced bronchoconstriction (EIB) occurs in 95 percent of
asthmatic children; therefore,
the performance of EIB testing is
also commonly performed.
The literature suggests correlation between severity of asthmatic symptoms and the severity
and degree of EIB.2,3,4 The American Association for Respiratory
Care published a clinical practice
guideline (CPG) in 1992 to
address bronchial provocation
testing.5 Subsequently, two chapters in the American Thoracic
Society (ATS) “Pulmonary Function Laboratory Management
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and Procedure Manual” address
the methacholine challenge test
and the exercise challenge test.6
Most recently, in January 2000,7
the ATS published guidelines for
methacholine and exercise testing. The AARC Bronchial Provocation CPG is under revision and
will be published later this year to
reflect changes in practice and
recommendations over the past
several years.
This article will highlight portions of the ATS guidelines for
methacholine and exercise challenge testing. For laboratories
performing bronchial challenge
testing, a thorough review of the
entire document is required.
G u i d elin e pu r pose
The intended purpose of the
ATS guideline is to outline specific details associated with the
two most widely used bronchial
provocation methods: methacholine and exercise. It does not
limit the use of alternative methods when the procedure or protocol has been well established in
the literature. Methacholine
challenge testing is better established than exercise. The document is directed at performance
of these two methods in a
patient population that can perform good-quality spirometry.
I n dication s an d
con tr ain dication s
Methacholine challenge testing will have the greatest diagnostic value when the pretest
probability is between 30 and 70
percent. Its negative predictive
power exceeds the positive predictive power; therefore, it
becomes more useful in excluding a diagnosis of asthma. The
exercise challenge test is
Clinical Perspectives
selected to make the diagnosis of
EIB in an asthmatic patient with
symptoms related to exercise. A
negative response to methacholine does not exclude EIB.
It is important to include a
pretest interview and/or questionnaire with the testing session to identify possible contraindications. The contraindications are grouped into categories that may impact the
quality of the test or subject the
patient to increased risk or discomfort. Contraindications are
further defined as absolute or
relative. These contraindications include the ability to perform reliable spirometry maneuvers, the degree of airflow
limitation, history of cardiovascular problems, pregnancy, nursing mothers, and current use of a
cholinesterase inhibitor. In addition, if exercise is performed,
additional contraindications
apply, as well as recommended
monitoring with a 12-lead electrocardiogram for patients
greater than 60 years of age.
Te c hno lo g i s t t r a i n i n g
a nd s a f et y i s s u e s
The technologist training and
competence assessment remains the responsibility of the
pulmonary laboratory director,
but minimum recommendations are addressed in the ATS
document.
The first recommendation
states the technologist should be
familiar with this document and
the specific testing procedures.
In addition, one should be able
to manage all equipment used
for testing, perform spirometry
proficiently, recognize contraindications, know safety and
emergency procedures, know
when to terminate testing, and
a good precautionary measure to
perform a methacholine challenge on each technologist
responsible for testing patients.
P atien t prepar ation
Careful attention
to patient
preparation is
essential.
administer and evaluate responsiveness to bronchodilators.
The safety of both the patient
and technologist should be considered with methacholine challenge testing. Consideration of
the safety issues is included in
the test procedure and the
design of the testing area. Specific attention must be given to
the availability of medications to
treat severe bronchospasm,
both for inhalation and subcutaneous injection. Oxygen must be
available. Other equipment that
should be available includes a
pulse oximeter, stethoscope, and
sphygmomanometer. Technologist exposure to methacholine
should be minimized. It may be
Careful attention to patient
preparation is essential. In my
experience, a primary reason for
canceling this procedure is a lack
of adequate patient preparation.
Upon scheduling the patient, a
list of medications to withhold
and the specific amount of time
to withhold each medication
must be given to the patient. In
addition, verbal communication
between the patient and technologist a few days pretest may
prove beneficial.
Just prior to testing, the procedure is explained, informed
consent signed (when required),
medications reviewed, and an
evaluation for contraindications
is completed.
Meth ach olin e ch oice
an d prepar ation
Although the document
states that industrial sources of
methacholine appear to work as
well as Provocholine, there are
definite advantages to U.S. Food
and Drug Administration(FDA) approved methacholine.
Provocholine is approved for
human use and is required to
meet good manufacturing practices for quality, purity, and consistency. Methapharm Inc.,
based in Brantford, ON,
Canada, is currently the sole
provider of FDA-approved
methacholine (Provocholine).
The guidelines committee
members made a special note
concerning their preference for
normal saline without phenol as
the diluent, but there is no evidence that adding or not adding
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Clinical Perspectives
preservative impacts the test
results. Both are considered an
acceptable diluent, but buffered
solutions should not be used as
the diluent.
The mixing of the methacholine solutions should be performed by a pharmacist or welltrained individual. Storage
instructions vary based on the
source of the methacholine.
The methacholine should be at
room temperature when the
testing is performed.
P ro to c o ls
The ATS guidelines committee narrowed the protocol recommendation for methacholine
challenges to two: the 2-min.
tidal breathing method and the
five-breath dosimeter technique. The reader is referred to
the document for a detailed
description of each protocol.
Two dosing schedules are recommended. The first is a doubling
schedule beginning with 0.031
mg/mL, and the second is a fourfold schedule beginning with
0.0625 mg/mL. The two protocols described in the statement
are those most widely used in
North America and Europe.
Exercise testing is performed
with either a motor-driven
treadmill or an electromagnetically braked cycle ergometer.
Q ua lity a s s u r a n c e
Nebulizer output is critical to
obtaining valid results. Each
nebulizer should be tested to
verify that it meets the specifications for either the tidal
breathing method or the fivebreath dosimeter method. The
method for verifying nebulizer
output varies based on the
method selected. Two nebulizers for performing the metha-
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references
1. Scott, G.C., & Braun, S.R. (1991). A
survey of the current use and methods of analysis of bronchoprovocational challenges. Chest, 100(2),
322-328.
2. Godfrey, S. (1975). Exerciseinduced asthma — Clinical, physiological, and therapeutic implications.
Journal of Allergy and Clinical
Immunology, 56(1), 1-17.
3. Godfrey, S., & Bar-Yishay, E.
(1993). Exercise-induced asthma
revisited. Respiratory Medicine, 87(5),
331-344.
4. Godfrey, S., Springer, C., Noviski,
N., et al. (1991). Exercise but not
choline
challenges
are
described in the guidelines: the
DeVilbiss 646 and the English
Wright nebulizer.
The quality of the actual test
maneuvers impacts the interpretation of test results. High-quality baseline testing should be
obtained. Other tests, such as
the forced inspiratory maneuver,
body plethysmography, transcutaneous oxygen, and forced
oscillation are described as alternatives when the patient cannot
perform reliable spirometry.
Each of these tests may be indicated based on the age of the
patient, clinical indication, and
ability to reliably perform each
test maneuver.
The document also addresses
data presentation and interpretation of the results. Attention
to detail is imperative in
bronchial provocation testing.
Multiple variables exist and
should be controlled to yield reliable test results. b
Susan Blonshine is the director of
TechEd, a diagnostics consulting service in Michigan. She is the AARC’s
official representative to NCCLS (the
methacholine differentiates asthma
from chronic lung disease in children.
Thorax, 46(7), 488-492.
5. American Association for Respiratory Care. (1992). Clinical practice
guideline: Bronchial provocation.
Respiratory Care, 37(8), 902-906.
6. American Thoracic Society. (1998).
Pulmonary function laboratory management and procedure manual. New
York, NY: American Thoracic Society.
7. American Thoracic Society. (2000).
Guidelines for methacholine and
exercise challenge–1999. American
Journal of Respiratory and Critical
Care Medicine, 161(1), 309-329.
National Committee for Clinical Laboratory Standards), and she chaired
the Association’s Diagnostics Section
from 1995 to 1997.