Shortness of Breath
Robert M. Theal
Shortness of breath, or dyspnea, accounts for 3.7% of all visits to medical clinics (1).
Approach
The initial history, physical examination, and chest x-ray (CXR) study are diagnostic in 66% to 92% of the patients (1). This symptom is present in many different illnesses. Fortunately, only a handful of disorders cause most of the cases; therefore, the most economical approach is to exclude acute life-threatening problems during the initial clinical examination. These include pneumonia, pulmonary embolus, acute heart failure, toxic exposure or ingestion, myocardial infarction, pneumothorax, life-threatening neuromuscular disease, or airway obstruction. If these are unlikely, then the next step is to systematically evaluate the patient for the most frequent disorders using common tests.
Shortness of breath has a long differential diagnosis, but respiratory and cardiac diseases account for 85% of the cases; in the remaining 15%, only a few illnesses are usually found (3). Of all the final diagnoses in dyspneic patients, the frequency of asthma is 18% to 33% and chronic obstructive pulmonary disease is 9% to 19% (1–4). Congestive heart failure (CHF) or pulmonary edema represents 11% to 63% of the cases (1–4). Other important diagnoses are deconditioning or obesity in 3% to 5% (1–4). Final diagnoses ranging between 0% and 10% include interstitial lung disease and ischemic heart disease (1–4). Table 8.3 lists less common diagnoses.
History
Are historical features helpful? Historical findings are neither sensitive nor specific; however, some symptoms are associated with specific diseases. Regardless of the cause, people associate shortness of breath with words that describe a sense of “work” or “effort” to breathe. Asthma is associated with words that denote a sense of “tightness.” Patients with interstitial lung disease choose terms emphasizing the sense of “rapid” breathing. Did the patient select terms indicating difficulty with both inhalation and exhalation? This is often reported by patients with CHF (Chapter 7.5). Patients who are deconditioned select rapid, breathing more, or heavy to describe their dyspnea. Patients suffering from neuromuscular disorders select terms denoting rapid breathing or difficulty with inhalation. Is the patient aged less than 40 years? Are the patient’s symptoms episodic? Reactive airway disease and hyperventilation are associated with these terms (2).
Physical examination
In the physical examination, focus on signs of respiratory or cardiac disease. For the respiratory system, this means a careful examination starting at the nose. Specifically, on head, eyes, ear, nose, and throat examination look for evidence of obstruction, infection, or postnasal drip. Exclude obstruction, subcutaneous emphysema, or tracheal deviation. On cardiac examination, look for evidence of cardiomegaly, S3 gallop, or hepatojugular reflux (HJR). In this setting, HJR is very specific for CHF (1). Assess the lungs for abnormal breath sound intensity, rales, wheezing, rhonchi, or tachypnea. Examine the chest for abnormal movements or deformities. Exclude abdominal masses, ascites, pregnancy, or abdominal distention. Evaluate the extremities for edema, tenderness, or asymmetry. Do a complete neurologic examination, and screen for weakness atrophy, sensory loss, and fasciculations.
Testing
Most patients require a CXR study and pulse oximetry to screen for cardiac and pulmonary diseases. Use an arterial blood gas (ABG) analysis to confirm hypoxia, hypercapnia, hypocapnia, and acidosis. Complete blood count (CBC), electrolytes, thyroid-stimulating hormone (TSH), and drug screens are useful for suspected cases of anemia, acidosis, hyperthyroidism, hypothyroidism, or drug ingestions.
Pulmonary function studies (PFTs) are important to document the presence of obstructive or restrictive lung diseases. A methacholine challenge test is used if the symptoms are intermittent, the patient is aged less than 40 years, or if lung disease is suspected and the PFTs are normal. In this setting, the results will confirm or exclude asthma (3). In dyspneic patients, a lung diffusion capacity (DLCO) has a high positive predictive value and a high negative predictive value for interstitial lung disease (3). Low maximal inspiratory and expiratory pressures suggest neuromuscular disease.
The cardiac causes of dyspnea are CHF, intracardiac shunts, valvular heart disease, pulmonary hypertension, and pericardial disease. They have abnormal or characteristic findings on echocardiography and Doppler echocardiography. An electrocardiogram (ECG) or exercise stress test (EST) screens for arrhythmias and ischemic heart disease. Warning: A negative EST does not exclude ischemia in dyspneic patients (3) (Chapter 7.1).
Other tests are used in selected patients. High resolution computerized tomography (CT) of the chest detects early interstitial lung disease in patients with normal CXR films. Electromyogram (EMG) and nerve conduction studies are useful for confirming and differentiating the most common neuromuscular problems: myasthenia gravis and Guillain-Barré syndrome. A therapeutic response to H2 blockers confirms gastroesophageal reflux disease (GERD) in most dyspneic patients (2). Screen for acute or chronic pulmonary embolism with a nuclear medicine ventilation and perfusion (·V/Q·) scan.
Diagnostic assessment
The initial assessment usually requires a clinical evaluation, CXR study, and pulse oximetry. This identifies about 70% of the underlying diseases (1). For the remainder, a systematic evaluation for the most common diseases will correctly identify the cause. If appropriate, consider obtaining an ECG, CBC, TSH, and electrolytes. If theses are nondiagnostic, then further testing is indicated.
Exclude pulmonary diseases if the initial evaluation is nondiagnostic, or if pulmonary diseases are suspected, which account for 75% of the cases (3). Start with PFTs and an ABG. If the PFTs are normal, then order a methacholine challenge test to rule out asthma. If interstitial lung disease is suspected or if the PFTs show a restrictive pattern, then order a DLCO. Abnormally low maximal inspiratory and expiratory pressures suggest neuromuscular disease. Confirm the diagnosis with an EMG.
When pulmonary disease has been excluded, or if cardiac disease is suspected, the next step should be a cardiac evaluation. An echocardiogram will suggest or identify most of the cardiac causes. If the echocardiogram is normal, consider exercise stress testing or a Holter monitor. If these are normal, then most patients will have either GERD, deconditioning, or psychogenic disorders. Other low frequency causes of shortness of breath that need further evaluation include neuromuscular diseases, pulmonary emboli, postnasal drip, and sleep apnea. With a clinical suspicion of these disorders, obtain an EMG, ·V/Q· scan, or polysomnogram. Otherwise, they are not indicated.
References
1. Mulrow CD, Lucey CR, Farnett LE. Discriminating causes of dyspnea through clinical examination. J Gen Intern Med 1993;8:383–392.
2. DePaso WJ, Winterbauer RH, Lusk JA, Dreis DF, Springmeyer SC. Chronic dyspnea unexplained by history, physical examination, chest roentgenogram, and spirometry. Chest 1991;100:1293–1299.
3. Pratter MR, Curley FJ, Dubois J, Irwin RS. Cause and evaluation of chronic dyspnea in a pulmonary disease clinic. Arch Intern Med 1989;149:2277–2282.
4. Schmitt BP, Kushner MS, Wiener SL. The diagnostic usefulness of the history of the patient with dyspnea. J Gen Intern Med 1986;1:386–393.
5. Mahler DA, Harver A, Lentine T, Scott JA, Beck K, Schwartzstein M. Descriptors of breathlessness in cardiorespiratory diseases. Am J Respir Crit Care Med 1996;154:1357–1363.
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Book Source Details
- Book Title: The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter
- Author(s): Robert B. Taylor (editor)
- Year of Publication: 2000
- Copyright Details: The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter, Copyright © 2000 Lippincott Williams & Wilkins.
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Copyright Details: The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter, Copyright © 2008 Williams & Wilkins.
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