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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
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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.
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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.
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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:
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- 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 ...