Harrison's Internal Medicine Part 2. Cardinal Manifestations and Presentation of Diseases Section 6. Alterations in Gastrointestinal Function Chapter 33. Dyspnea and Pulmonary Edema Dyspnea 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. . | Chapter 033. Dyspnea and Pulmonary Edema Part 1 Harrison s Internal Medicine Part 2. Cardinal Manifestations and Presentation of Diseases Section 6. Alterations in Gastrointestinal Function Chapter 33. Dyspnea and Pulmonary Edema Dyspnea 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. Mechanisms of Dyspnea Respiratory sensations are the consequence of interactions between the efferent or outgoing motor output from the brain to the ventilatory muscles feedforward 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 . A given disease state may lead to dyspnea by one or more mechanisms some of which may be operative under some circumstances but not others. Figure 33-1 Algorithm fqrthe Inputs in Dyspnea Production twk Baud AS Kafpar DL. Briunwatd f. Uvi r BL. Lanpp OL. Jamaf fi JL. LGiCiisfl Jl H rrisofi s A jwijp ar AT Æcj. . 17th Edibon. cc 5imedkiri .qorri Cspwrtflhi Th Mcijr u-Hill CempanHi lot AU riah c Armvij. Hypothetical model for integration of sensory inputs in the production of dyspnea. Afferent information from the receptors throughout the respiratory system projects directly to the sensory cortex to contribute to primary qualitative sensory experiences and provide feedback on the action of the ventilatory pump. Afferents also project to the areas of the brain responsible for control of ventilation. The motor cortex responding to input from the control centers sends neural messages to the ventilatory muscles and a corollary .
