Dyspnea

Definition

Abnormally uncomfortable awareness of breathing; intensity quantified by establishing

the amount of physical exertion necessary to produce the sensation.

Dyspnea occurs when work of breathing is excessive.

Causes

HEART DISEASE

• Dyspnea most commonly due toqpulmonary capillary pressure,and sometimes

fatigue of respiratory muscles. Vital capacity and lung compliance arep

and airway resistanceq.

• Begins as exertional breathlessness : orthopnea : paroxysmal nocturnal

dyspnea and dyspnea at rest.

• Diagnosis depends on recognition of heart disease,e.g., Hx of MI, presence

of S3, S4,murmurs, cardiomegaly,jugular vein distention, hepatomegaly, and

peripheral edema (Chap. 126). Objective quantification of ventricular function

(echocardiography,radionuclide ventriculography) is often helpful.

AIRWAY OBSTRUCTION (Chap. 133)

• May occur with obstruction anywhere from extrathoracic airways to lung

periphery.

• Acute dyspnea with difficulty inhaling suggests upper airway obstruction.

Physical exam may reveal inspiratory stridor and retraction of supraclavicular

fossae.

• Acute intermittent dyspnea with expiratory wheezing suggests reversible

intrathoracic obstruction due to asthma.

• Chronic,slowly progressive exertional dyspnea characterizes emphysema

and CHF.

• Chronic cough with expectoration is typical of chronic bronchitis and bronchiectasis.

DIFFUSE PARENCHYMAL LUNG DISEASES (Chap. 136) Many

parenchymal lung diseases,from sarcoidosis to pneumoconioses, may cause

dyspnea. Dyspnea is usually related to exertion early in the course of the illness.

Physical exam typically reveals tachypnea and late inspiratory rales.

PULMONARY EMBOLISM (Chap. 135) Dyspnea is most common

symptom of pulmonary embolus. Repeated discrete episodes of dyspnea may

occur with recurrent pulmonary emboli; tachypnea is frequent.

DISEASE OF THE CHEST WALL OR RESPIRATORY MUSCLES

(Chap. 137) Severe kyphoscoliosis may produce chronic dyspnea,often with

chronic cor pulmonale. Spinal deformity must be severe before respiratory function

is compromised.

Pts with bilateral diaphragmatic paralysis appear normal while standing,but

complain of severe orthopnea and display paradoxical abnormal respiratory

movement when supine.

Approach to the Patient

Elicit a description of the amount of physical exertion necessary to produce the

sensation and whether it varies under different conditions.

• If acute upper airway obstruction is suspected,lateral neck films or fiberoptic

exam of upper airway may be helpful.

• With chronic upper airway obstruction the respiratory flow-volume curve

may show inspiratory cutoff of flow,suggesting variable extrathoracic obstruction.

• Dyspnea due to emphysema is reflected in a reduction in expiratory flow

rates (FEV1),and often by a reduction in diffusing capacity for carbon monoxide

(DLCO).

• Pts with intermittent dyspnea due to asthma may have normal pulmonary

function if tested when asymptomatic.

Differentiation between Cardiac and Pulmonary Dyspnea

• Careful history: Dyspnea of lung disease usually more gradual in onset than

that of heart disease; nocturnal exacerbations common with each.

• Examination: Usually obvious evidence of cardiac or pulmonary disease.

Findings may be absent at rest when symptoms are present only with exertion.

• Brain natriuretic peptide (BNP): Elevated in cardiac but not pulmonary

dyspnea.

• Pulmonary function tests: Pulmonary disease rarely causes dyspnea unless

tests of obstructive disease (FEV1,FEV 1/FVC) or restrictive disease (total lung

capacity) are reduced (_80% predicted).

• Ventricular performance: LV ejection fraction at rest and/or during exercise

usually depressed in cardiac dyspnea.

• Cardiac dyspnea usually begins as breathlessness on strenuous exertion with

gradual (months-to-years) progression to dyspnea at rest.

• Pts with dyspnea due to both cardiac and pulmonary diseases may report

orthopnea. Paroxysmal nocturnal dyspnea occurring after awakening from sleep

is characteristic of CHF.

• Dyspnea of chronic obstructive lung disease tends to develop more gradually

than that of heart disease.

• PFTs should be performed when etiology is not clear. When the diagnosis

remains obscure a pulmonary stress test is often useful.

• Management depends on elucidating etiology.