Dyspnea and pulmonary edema

Distinguishing Cardiogenic from Noncardiogenic Pulmonary Edema The history is essential for assessing the likelihood of underlying cardiac disease as well as for identification of one of the conditions associated with noncardiogenic pulmonary edema. The physical examination in cardiogenic pulmonary edema is notable for evidence of increased intracardiac pressures (S3 gallop, elevated jugular venous pulse, peripheral edema), and rales and/or wheezes on auscultation of the chest.

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Approach to the Patient: Dyspnea (Fig. 33-3) In obtaining a history, the patient should be asked to describe in his/her own words what the discomfort feels like, as well as the effect of position, infections, and environmental stimuli on the dyspnea. Orthopnea is a common indicator of congestive heart failure, mechanical impairment of the diaphragm associated with obesity, or asthma triggered by esophageal reflux. Nocturnal dyspnea suggests congestive heart failure or asthma.

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Distinguishing Cardiovascular from Respiratory System Dyspnea If a patient has evidence of both pulmonary and cardiac disease, a cardiopulmonary exercise test should be carried out to determine which system is responsible for the exercise limitation. If, at peak exercise, the patient achieves predicted maximal ventilation, demonstrates an increase in dead space or hypoxemia (oxygen saturation below 90%), or develops bronchospasm, the respiratory system is probably the cause of the problem.

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Differential Diagnosis Dyspnea is the consequence of deviations from normal function in the cardiopulmonary systems. Alterations in the respiratory system can be considered in the context of the controller (stimulation of breathing); the ventilatory pump (the bones and muscles that form the chest wall, the airways, and the pleura); and the gas exchanger (the alveoli, pulmonary vasculature, and surrounding lung parenchyma). Similarly, alterations in the cardiovascular system can be grouped into three categories: conditions associated with high, normal, and low cardiac output (Fig. 33-2).

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Integration: Efferent-Reafferent Mismatch A discrepancy or mismatch between the feed-forward message to the ventilatory muscles and the feedback from receptors that monitor the response of the ventilatory pump increases the intensity of dyspnea. This is particularly important when there is a mechanical derangement of the ventilatory pump, such as in asthma or chronic obstructive pulmonary disease (COPD).

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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.

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