Case
Study: Bronchial Provocation in Dyspnea
The patient
who seeks medical consultation because of shortness of breath, difficulty
breathing, fatigue and so forth is usually subjected to a series of
questions, a physical examination, chest x-ray, spirometry, etc. These
studies, when taken individually, usually do not provide the answer,
but collectively shed light on the problem. When taking a clinical history
from a patient complaining of dyspnea, we attempt to quantitate the
symptoms in terms of onset, magnitude and methods of reducing the severity
of the symptoms.
In the
case of the patient with suspected reactive airways disease, it is often
necessary to challenge the airway to determine the degree of reactivity.
In such cases a methacholine challenge is often ordered. The symptoms
of chest tightness, breathlessness, etc., produced by the reactive airways
disease, and produced during testing in patients with the disease are
in part due to the hyperinflation that accompanies the bronchospasm.
A positive test by traditional pulmonary function testing is regarded
as a 20% change from baseline measurement of the FEV1. In some situations,
there may be no change in the FEV1 as demonstrated in the following
case study.
Case
Study
A 19-year-old
female (height 5'6", weight 125 lbs) presents with symptoms of
cough and breathlessness which at times is not related to specific events
or activities. The following pulmonary function tests are obtained:
|
Spirometry
|
Methacholine
Challenge
|
|
Actual |
Predicted |
Dose |
%
Change FEV |
| FVC
(L) |
3.73 |
91 |
0.025 |
0.2 |
| FEV1
(L) |
2.92 |
81 |
1.400 |
0 |
| FEV1/FVC |
88% |
|
14.00 |
0.6 |
| FEF
25-75 |
2.59 |
60 |
189 |
0 |
|
Plethysmography
Values
|
|
Pre-Challenge |
Post-Challenge |
%
Change |
Post
Bronch. |
| VTG |
2.94 |
3.54 |
20 |
2.77 |
| RV |
1.51 |
2.50 |
65 |
1.56 |
| sRaw |
7.01 |
9.54 |
36 |
6.17 |
| sGaw |
0.14 |
0.10 |
-30 |
0.16 |
The above
testing reveals a significant increase in thoracic gas volume, residual
volume and total capacity with methacholine challenge. Airway resistance
increased and conductance decreased similarly, and all values returned
to baseline with the inhalation of bronchodilator therapy, while the
FEV1 from spirometry did not show any signs of reduction when challenged.
The patient was started on bronchodilator therapy which resulted in
improvement in symptoms.
Pulmonary
function tests are commonly thought to consist of spirometry which includes
vital capacity, timed lung volumes and peak flows. Plethysmographic
measurement of airway resistance and conductance is a more sensitive
tool to determine the presence of airway disease. It can differentiate
between central and peripheral disease. It can also differentiate between
bronchospastic disease and emphysema as a cause of hyperinflation. Finally,
Raw and Gaw are a more sensitive test of the responsiveness of airways
to inhaled bronchodilators.
By tradition,
a primary or referring physician may request spirometry as a preliminary
to the evaluation of dyspnea, confirmation of a diagnosis of asthma,
or in an attempt to determine risk for post operative pulmonary complications.
With the exception of asthma, these studies are not in themselves diagnostic
of any particular entity. Spirometry alone cannot measure all lung volumes,
nor can it measure and differentiate all levels of airway resistance.
Acknowledgement
Edward
D. Sivak, M.D., FACP, FCCP, FCCM. Professor of Medicine, Chief, Division
of Pulmonary and Critical Care, State University of New York, Health
Science Center, Syracuse, NY
