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Anxiety
is a frequent manifestation of pulmonary diseases and the prevalence
of panic disorder is higher in patients with chronic lung disease
than in matched, healthy controls (Smoller
et al., 1996). The reverse is also true: patients with anxiety
disorders frequently report symptoms of dyspnea, chest pain, palpitations,
and a tingling or prickling sensation in the extremities (paresthesias).
Patients experiencing an acute anxiety disorder may also experience
hyperventilation with hypocapnia. Three models have been proposed
to explain the relationship between dyspnea, hyperventilation,
and anxiety disorders (Smoller
et al., 1996).
| Figure
32.1 Schematic Representation of Three Models of the
Relationship between Dyspnea, Hyperventilation (HV), and Panic
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| Official
Journal of the American Thoracic Society. © American
Lung Association. Reprinted with permission. |
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The hyperventilation
model postulates that an increased ventilation leads to an acute
respiratory alkalosis, the consequences of which are breathing
discomfort and anxiety. The second model, a cognitive-behavioral
model, suggests that individuals misinterpret physical sensations
leading to a positive feedback cycle of anxiety leading to more
symptoms leading to more anxiety. The third model proposes an
abnormality in the central chemoreceptor such that a given stimulus
leads to an over-exuberant response of the respiratory controller
and an associated sense of dyspnea and panic/anxiety.
In patients with expiratory
airflow obstruction, anxiety may also lead to a breathing pattern
that precipitates physiological changes that can produce dyspnea.
As respiratory rate rises, a common manifestation of anxiety,
the patient with expiratory airflow obstruction has insufficient
time to exhale. This leads to hyperinflation with an increased
work of breathing and a sense of greater effort to breathe, and
may be accompanied by the sensation of an "unsatisfying breath"
. Breathing retraining techniques, commonly employed in pulmonary
rehabilitation programs, are designed to break this cycle of rapid
breathing, hyperinflation, more distress, and even faster, more
shallow breaths. To the extent that one can provide the patient
with strategies for dealing with their symptoms and attendant
fears, the individual may establish a sense of control over his
or her body that may pre-empt the development of anxiety and hyperventilation.
Exercise training, by repeatedly exposing the patient to breathing
discomfort under safe, monitored conditions, may also "desensitize"
the patient to the fear associated with the sensations of dyspnea
(Carrieri-Kohlman et
al., 1996).
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