Acute Dyspnea

Differential Overview

❑ Asthma

❑ COPD exacerbation

❑ Left heart failure

❑ Pneumonia

❑ Pulmonary embolism

❑ Pneumothorax

❑ Hyperventilation

❑ Pleural effusion

❑ Pericardial tamponade

❑ Upper airway obstruction

❑ Pulmonary hypertension

❑ Lung cancer

❑ Noncardiogenic pulmonary edema

❑ Bilateral diaphragmatic paralysis

Diagnostic Approach

Dyspnea is a sensation of inability to take in enough air, which causes anxiety and discomfort. Being caused by factors including tissue hypoxia, reduced lung compliance, and activation of J receptors, it may not correlate reliably with arterial oxygen saturation.

Paroxysmal nocturnal dyspnea occurs in congestive heart failure (CHF) when the patient awakens with a sense of suffocation. A patient with chronic bronchitis may also awaken with shortness of breath and wheezing caused by mucous plugging; this clears with a cough. Orthopnea is seen in CHF, asthma, and bilateral diaphragmatic paralysis. Sudden onset suggests pneumothorax, pulmonary embolism, or “flash” pulmonary edema.

Tachypnea can occur without dyspnea in conditions such as metabolic acidosis.

Clinical Findings

Asthma  Diffuse wheezing occurs without fever. The patient will complain of chest tightness. There will usually be a history of prior asthma, croup, or atopy. Mild bronchospasm may present with vague dyspnea (especially exertional) and cough. An acute increase in shortness of breath can occur with plugging of tenacious mucous. A severe asthma exacerbation is marked by low SaO₂, inability to speak full sentences, and a paucity of airflow (both on peak flow and on chest auscultation). The degree of pulsus paradoxus (paradox) provides a quantative measure of severity.

COPD exacerbation  Diffuse wheezing with productive cough occurs in smokers with chronic bronchitis, usually when an upper respiratory infection develops. The patient complains of an increased effort to breathe and a sense of not being able to take a deep breath.

Left heart failure  The patient has a sensation of air hunger or suffocation. Acute left heart failure usually occurs in the setting of myocardial ischemia, so substernal chest pain/discomfort is common. Orthopnea, paroxysmal nocturnal dyspnea, and S₃ gallop are helpful clues. Interstitial edema is marked by tachypnea and rales, which are inspiratory and dependent. Alveolar edema produces wet rales/rhonchi, anxiety, and frothy, blood-tinged sputum.

Pneumonia  Fever, productive cough, and consolidative findings (localized rales, egophony, and diminished breath sounds) are characteristic. Subacute onset of dyspnea in an HIV-positive patient suggests Pneumocystis.

Pulmonary embolism  Thromboembolism is recognized by acute pleuritic chest pain, hemoptysis (with pulmonary infarction), an embolic source in the legs, and factors predisposing to deep venous thrombosis. A pleural friction rub occurs in 20%.

Pneumothorax  The onset is acute, with unilateral diminished breath sounds and hyperresonance to percussion. It usually occurs in thin, young adults or older patients with bullous disease. A tracheal shift suggests tension pneumothorax.

Hyperventilation  It is recognized by the concurrence of perioral and acral paresthesias, the stressful setting in which it occurs, and perceived anxiety.

Pleural effusion  Unilateral diminished breath sounds and percussive dullness are found.

Pericardial tamponade  Findings of jugular venous distension with Kussmaul sign (veins fill with inspiration), exaggerated pulsus paradoxus, and hypotension are key clues.

Upper airway obstruction  Stridor and a tracheal wheeze are characteristic. Sudden aphonia while eating occurs with tracheal obstruction by a food bolus, a medical emergency. Other causes include severe laryngitis, diphtheria, and allergic laryngeal edema.

Pulmonary hypertension  An accentuated pulmonary component of the second heart sound, and right ventricular lift are suggestive.

Lung cancer  Acute dyspnea can occur with bronchial obstruction and lobar collapse. A unilateral wheeze and absent segmental breath sounds, are found. The patient is most frequently a smoker.

Noncardiogenic pulmonary edema  This occurs in the setting of infection, aspiration, shock, narcotic or salicylate overdose, high altitude, or CNS events. With salicylate intoxication, central hyperventilation occurs.

Bilateral diaphragmatic paralysis  This is a cause of acute dyspnea in neurologic or myopathic disorder, recent thoracic trauma, or surgery.

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Book Source Details

• Book Title: Field Guide to Bedside Diagnosis
• Author(s): David S. Smith
• Year of Publication: 2007
• Copyright Details: Field Guide to Bedside Diagnosis, Copyright © 2007 Lippincott Williams & Wilkins.

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Copyright Details: Field Guide to Bedside Diagnosis, Copyright © 2008 Williams & Wilkins.

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More About This Book: Title: Field Guide to Bedside Diagnosis Authors: David S. Smith Publisher: Lippincott Williams & Wilkins Copyright: 2007 ISBN: 0-78178-165-5

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