Chapter 65

Common respiratory symptoms that bring patients to the ED include dyspnea (sometimes with the associated findings of hypoxia and hypercapnia), wheezing, and cough. Hiccups are an infrequent presenting symptom, but when persistent, they are very distressing to the patient. Cyanosis can be associated with pulmonary, vascular, and hematologic conditions. Pleural effusion can be caused by a variety of pulmonary and cardiac diseases. This chapter discusses these symptoms, signs, and disorders as they relate to evaluation of emergency patients. Despite the increasing availability of and reliance on ancillary tests, the assessment of patients still begins with an accurate history and a careful physical examination to make the wisest use of ancillary tests.1

Dyspnea is a subjective feeling of difficult, labored, or uncomfortable breathing, which patients often describe as “shortness of breath,” “breathlessness,” or “not getting enough air.” Dyspnea does not result from a single pathophysiologic mechanism, but approximately two thirds of symptomatic patients presenting to the ED have a cardiac or a pulmonary disorder.

Dyspnea is frequently associated with other respiratory symptoms. Tachypnea is rapid breathing; it may or may not be associated with dyspnea. Orthopnea is dyspnea in the recumbent position. It is most often the result of left ventricular failure, but can also be seen with diaphragmatic paralysis or chronic obstructive pulmonary disease (COPD). Paroxysmal nocturnal dyspnea is orthopnea that awakens the patient from sleep. Trepopnea is dyspnea associated with only one of several recumbent positions. Trepopnea can occur with unilateral diaphragmatic paralysis, with ball-valve airway obstruction, or after surgical pneumonectomy. Platypnea is the opposite of orthopnea: dyspnea in the upright position. Platypnea results from the loss of abdominal wall muscular tone and, in rare cases, from right-to-left intracardiac shunting, as occurs from a patent foramen ovale. Hyperpnea is essentially hyperventilation and is defined as minute ventilation in excess of metabolic demand. Hyperpnea may not be associated with dyspnea, and dyspnea is not always associated with increased minute ventilation.

### Pathophysiology

Dyspnea is a complex sensation that involves both objective and subjective elements. Dyspnea has no defined neural pathway, and the perceived difficulty probably arises from the interaction of several pathophysiologic mechanisms.2 Input from any or all of the following receptors is integrated in a complex manner in the central nervous system (CNS) at both the subcortical and cortical levels:

• A conscious sense of the voluntary peripheral skeletal and respiratory muscular effort that occurs with increased work of breathing
• Stimulation of upper airway mechanical and thermal receptors
• Decreased stimulation of chest wall afferents
• Stimulation of central hypercapnic chemoreceptors in the central medulla
• Stimulation of peripheral hypoxic chemoreceptors, primarily in the carotid body in concert with those in the aortic arch
• Stimulation of a variety of lung receptors, including intraparenchymal pulmonary stretch receptors, airway irritant receptors, and unmyelinated receptors that respond to interstitial edema or a change in compliance
• Stimulation of peripheral vascular receptors, including the right atrial and left ...

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