Dyspnea

For further information, see CMDT Part 2-03: Dyspnea

Essentials of Diagnosis

• Inquire about

  • Fever; cough; chest pain

  • Vital signs; pulse oximetry

  • Chest and cardiac examination

  • Chest radiography

  • Arterial blood gas result (in selected patients)

General Considerations

• Defined as a subjective experience or perception of uncomfortable breathing

• Can result from primary pulmonary vasculopathy (pulmonary hypertension) or from psychogenic conditions or from conditions that

  • Increase the mechanical effort of breathing (eg, asthma, chronic obstructive pulmonary disease [COPD], restrictive lung disease, respiratory muscle weakness)

  • Produce compensatory tachypnea (eg, hypoxemia or acidosis)

• The following factors play a role in how and when dyspnea presents in patients:

  • Rate of onset

  • Previous dyspnea

  • Medications

  • Comorbidities

  • Psychological profile

  • Severity of underlying disorder

Symptoms

• Rapid onset, severe dyspnea in the absence of other clinical features should raise concern for

  • Pneumothorax

  • Pulmonary emboli

  • Increased left ventricular end-diastolic pressure (LVEDP)

• Spontaneous pneumothorax

  • Usually accompanied by chest pain

  • Occurs most often in thin, young males, or in those with underlying lung disease

• Pulmonary emboli should always be suspected when cause of dyspnea is not apparent or when a patient with new dyspnea reports

  • A recent history (previous 4 weeks) of prolonged immobilization or surgery

  • Estrogen therapy

  • Other risk factors of deep venous thrombosis (eg, previous history of thromboembolism, cancer, obesity, lower extremity trauma)

• Silent myocardial infarction

  • Occurs more frequently in diabetic persons and women

  • Can result in increased LVEDP, acute heart failure (HF), and dyspnea

• When cough and fever are present,

  • Pulmonary disease (particularly infections) is the primary concern

  • However, myocarditis, pericarditis, and septic pulmonary emboli can also present in this manner

• Chest pain

  • Should be further characterized as acute or chronic, pleuritic or exertional

  • Although acute pleuritic chest pain is the rule in acute pericarditis and pneumothorax, most patients with pleuritic chest pain in the outpatient clinic have pleurisy due to acute viral respiratory tract infection

  • Periodic chest pain that precedes the onset of dyspnea is suspicious for myocardial ischemia or pulmonary emboli

• Wheezing

  • Most cases due to acute bronchitis

  • Other causes include new-onset asthma, foreign body, and vocal cord dysfunction

• Interstitial lung disease and pulmonary hypertension should be considered in patients with symptoms (or history) of connective tissue disease

• When a patient reports prominent dyspnea with mild or no accompanying features, consider

  • Noncardiopulmonary causes of impaired oxygen delivery (anemia, methemoglobinemia, cyanide ingestion, carbon monoxide)

  • Metabolic acidosis due to a variety of conditions

  • Panic disorder

  • Neuromuscular disorders

  • Chronic pulmonary embolism

• Platypnea-orthodeoxia syndrome

  • Characterized by dyspnea and hypoxemia on sitting or standing that improves in the recumbent position

  • May be caused by an intracardiac shunt, pulmonary vascular shunt, or ventilation-perfusion mismatch

• Hyperthyroidism can cause dyspnea from

  • Increased ventilatory drive

  • Respiratory muscle weakness

  • Pulmonary hypertension

Physical Examination

• Should include focused evaluation of the head and neck, chest, heart, and lower extremities

• Visual inspection of the patient's respiratory pattern can suggest

  • Obstructive airway disease (pursed-lip breathing, use of accessory respiratory muscles, barrel-shaped chest)

  • Pneumothorax (asymmetric excursion)

  • Metabolic acidosis (Kussmaul respirations)

• Patients with impending upper airway obstruction (eg, epiglottitis, foreign body), or severe asthma exacerbation, sometimes assume a tripod position

• Maximum laryngeal height

  • Defined as the distance between the top of the thyroid cartilage and the suprasternal notch at end expiration

  • A measure of hyperinflation

• Absent breath sounds suggests a pneumothorax

• An accentuated pulmonic component of the second heart sound (loud P2) is a sign of

  • Pulmonary hypertension

  • Pulmonary emboli

Differential Diagnosis

• Pneumonia

• COPD

• Asthma

• Pneumothorax

• Pulmonary emboli

• Cardiac disease (eg, HF, acute myocardial infarction, valvular dysfunction, arrhythmia, cardiac shunt)

• Diffuse alveolar hemorrhage

• Metabolic acidosis

• Cyanide toxicity

• Methemoglobinemia

• Carbon monoxide poisoning

• Interstitial lung disease

• Pulmonary hypertension

Laboratory Findings

• Elevated blood levels of procalcitonin or C-reactive protein can support the diagnosis of pneumonia in equivocal cases

Imaging Studies

• Chest radiography

  • Confirms diagnosis of pneumonia

  • Fairly sensitive and specific for new-onset HF

  • End-expiratory chest radiography enhances detection of small pneumothoraces

• High-resolution chest CT

  • Useful in the evaluation of pulmonary embolism

  • Also provides information about interstitial and alveolar lung disease

• Helical ("spiral") CT

  • Useful in diagnosing pulmonary embolism

  • To minimize unnecessary testing and radiation exposure, a clinical decision rule (such as the modified Wells criteria or the PE rule-out criteria) should be used to estimate the pretest probability of a pulmonary embolism

Diagnostic Studies

• Serum or whole blood B-type natriuretic peptide (BNP or NT-proBNP) testing

• Arterial blood gas measurement

• Venous blood gas measurement

• Spirometry

• Pulse oximetry can be used in office setting

• Aimed at relieving the underlying cause

• Supplemental oxygen (unless significant hypercapnia is present or strongly suspected pending arterial blood gas measurement)

• Pulmonary rehabilitation programs may be helpful for patients with

  • Moderate to severe COPD

  • Interstitial pulmonary fibrosis

When to Refer

• Following acute stabilization, patients with advanced COPD should be referred to a pulmonologist, and patients with HF or valvular heart disease should be referred to a cardiologist

• Cyanide toxicity or carbon monoxide poisoning should be managed in conjunction with a toxicologist

• Lung transplantation for patients with advanced interstitial lung disease

When to Admit

• Impaired gas exchange from any cause or high risk of pulmonary emboli pending definitive diagnosis

• Suspected cyanide or carbon monoxide poisoning