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Harrison's Principles of Internal Medicine, 18e
| Part 2. Cardinal Manifestations and Presentation of Diseases > Section 5. Alterations in Circulatory and Respiratory Functions > |
Chapter 33. Dyspnea
Sections: Dyspnea, Pulmonary Edema, Further Readings.
Topics Discussed: dyspnea; pulmonary edema.
Excerpt:"The American Thoracic Society defines dyspnea as a "subjective experience of breathing discomfort that consists of qualitatively distinct sensations that vary in intensity. The experience derives from interactions among multiple physiological, psychological, social, and environmental factors and may induce secondary physiological and behavioral responses." Dyspnea, a symptom, must be distinguished from the signs of increased work of breathing.Respiratory sensations are the consequence of interactions between the efferent, or outgoing, motor output from the brain to the ventilatory muscles (feed-forward) and the afferent, or incoming, sensory input from receptors throughout the body (feedback), as well as the integrative processing of this information that we infer must be occurring in the brain (Fig. 33-1). In contrast to painful sensations, which can often be attributed to the stimulation of a single nerve ending, dyspnea sensations are more commonly viewed as holistic, more akin to hunger or thirst. A given disease state may lead to dyspnea by one or more mechanisms, some of which may be operative under some circumstances, e.g., exercise, but not others, e.g., a change in position.Disorders of the ventilatory..."
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