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Imagine
that you are embarking on a research study to investigate the
effect of acute high blood levels of carbon dioxide (hypercapnia)
on the sensation and intensity of dyspnea. An earlier study suggested
that dyspnea seemed to be the consequence of muscle work and effort
(Killian et al., 1984). More
recently, however, you have become aware of data suggesting that
acute hypercapnia may cause a sensation of "air hunger"
(Banzett et al., 1989). The
protocol requires normal subjects to breathe at a constant fixed
level of ventilation while the investigator adds carbon dioxide
to the inhaled gas.
Question
6.1
You should ask subjects
to rate:
 | Breathing
discomfort |
 | Effort |
 | Effort
and breathlessness |
 | It
doesn't matter |
Question
6.2
The sensations of
effort and breathlessness that are depicted in the figure below
are affected by hypercapnia:
| Similarly |
| Differently |
| Figure
6.1: The Mean Change in Effort and Breathlessness Ratings
for Each Subject for Conditions A (PCO2=40) and B (PCO2=50)
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| Official
Journal of the American Thoracic Society. Copyright
American Lung Association. Reprinted with permission. |
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