| |
Consider
the following table showing the number of patients selecting various
descriptors during the course of the albuterol treatment.
| Table
2.1: Number of Patients Selecting Each Descriptor of
Dsypnea at Baseline and After Each Albuterol Treatment
|
|---|
| Descriptor
| Pre
| Post
1
| Post
2
| Post
3
|
|---|
| Tight |
16
|
8
|
5
|
6
|
| Breathing
more |
1
|
11
|
12
|
6
|
| Work |
7
|
3
|
5
|
4
|
| Effort |
6
|
5
|
4
|
3
|
| Breath
does not go out |
7
|
5
|
4
|
4
|
| Official
journal of the American Thoracic Society. © American
Lung Association. Reprinted with permission. |
|
Note
that the number of patients selecting chest tightness to describe
their breathlessness decreased to a greater degree with successive
albuterol treatments than did the sensations of effort and work.
A similar phenomenon occurs in patients with COPD, which may produce
a variety of sensations emanating from the airways, chest wall,
and chemoreceptors. There is no single "dyspnea receptor"
which, when stimulated with an electrical impulse, produces a
respiratory sensation that is common to all the diseases that
are characterized by dyspnea.
Research
is increasingly showing that dyspnea symptoms arise from a number
of different mechanisms and that these mechanisms lead to qualitatively
distinct sensations (Simon et al.,
1989; Simon et al., 1990; Mahler et al., 1996). When studying dyspnea, therefore, it is not sufficient
to inquire about or measure a global rating of breathing discomfort.
Rather, one needs to focus on discrete sensations that are produced
by discrete mechanisms.
Finally,
dyspnea, like all symptoms, is a subjective experience. A given
stimulus, such as a particular level of hypoxemia, will likely
produce different intensities of discomfort in different individuals.
Furthermore, within a particular individual, the same stimulus
may be perceived differently over time as a consequence of experience,
expectations, and behavioral factors such as mood.
|