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The respiratory
system is replete with a variety of mechanoreceptors that monitor
changes in flow in the airways as well as changes in the volume
of the lungs and chest wall. Although information from these receptors
appears to be used in large part to assess the mechanical consequences
of efferent neurological activity to the ventilatory muscles,
stretch and irritant receptors along with c-fibers in the lungs
may provide primary sensory information to the brain via the vagus
nerve. This information appears to be processed in a manner that
leads to a perception of respiratory discomfort. For example,
a number of reports describe improvement in dyspnea among patients
in whom the vagus nerve was blocked (Guz
et al., 1971; Davies et al.,
1987).
As discussed previously,
acute bronchoconstriction produces several sensations including
chest tightness, an increased effort or work of breathing, and
a sense of air hunger (Moy, et al.,
2000). Although the sensation of increased effort or work
of breathing is also found when individuals with normal lung function
breathe through an external resistive load, the sensation of chest
tightness appears to be quite distinct.
Question
11.1
How might one design
an experiment to determine if an element of the breathlessness
associated with asthma arises from the lung?
 | Study
patients with bilateral lung transplants |
 | Attempt
to block pulmonary receptor activity during bronchoconstriction |
 | Study
patients with bronchoconstriction during mechanical ventilation |
 | All
of the above |
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