Shortness of Breath

Overview
Types of Dyspnea
Common Causes
Mechanisms
Evaluation
Management
When to Seek Medical Care
Connections
References & Research
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Overview

Shortness of breath — or dyspnea — is the subjective experience of breathing discomfort. It is one of the most common reasons for ambulance calls and ER visits, and a frequent reason adults stop exercising before they realize anything is wrong with their heart or lungs. Like chest pain, dyspnea can mean almost anything — deconditioning, anemia, anxiety, asthma, heart failure, pulmonary embolism, ILD, or cancer — and the workup is layered: a quick set of bedside vitals and an ECG narrow it down at the bedside, with imaging and pulmonary function tests filling in the rest.

Types of Dyspnea

Acute dyspnea — sudden onset over minutes to hours; suggests pulmonary embolism, pneumothorax, acute heart failure, asthma exacerbation, anaphylaxis, foreign-body aspiration.
Subacute dyspnea — days to weeks; often pneumonia, sub-acute heart failure, pleural effusion, or new ILD.
Chronic dyspnea — weeks to months; COPD, ILD, chronic heart failure, deconditioning, obesity, anemia.
Orthopnea — dyspnea worse lying flat; classic for heart failure.
Paroxysmal nocturnal dyspnea — waking from sleep with severe shortness of breath; heart failure.
Platypnea — dyspnea worse upright; rare; suggests intracardiac shunt or hepatopulmonary syndrome.
Exertional dyspnea — only with activity; deconditioning, mild heart or lung disease, anemia.

Common Causes

Heart failure — orthopnea, PND, leg edema, exertional dyspnea; one of the leading causes in older adults.
Asthma — episodic wheeze, cough, and dyspnea; often triggered by allergens, exercise, viral infections.
COPD — chronic productive cough and dyspnea, almost always with smoking history.
Pulmonary embolism — sudden dyspnea, pleuritic chest pain, tachycardia, possible hemoptysis.
Pneumonia — fever, cough, focal lung exam.
Interstitial lung disease — progressive dyspnea, dry cough, Velcro crackles.
Pneumothorax and pleural effusion — sudden unilateral chest pain and dyspnea.
Anemia — fatigue and exertional dyspnea, often pallor.
Obstructive sleep apnea — daytime sleepiness, morning headaches; over time cardiopulmonary effects produce dyspnea.
Obesity hypoventilation syndrome — especially BMI >35 with daytime hypercapnia.
Anxiety and panic disorder — air hunger, hyperventilation, chest tightness; diagnosis of exclusion.
Deconditioning — gradual exertional dyspnea after prolonged sedentary period or illness.
Vocal-cord dysfunction — episodic stridor and dyspnea, often misdiagnosed as asthma.

Mechanisms

Increased respiratory drive — from hypoxemia, hypercapnia, acidosis, anemia, or anxiety stimulates chemoreceptors and produces air hunger.
Increased work of breathing — airway obstruction (asthma, COPD), reduced compliance (ILD, pulmonary edema), or chest-wall restriction (obesity, neuromuscular weakness).
Impaired gas exchange — ventilation-perfusion mismatch, shunt, diffusion impairment.
Cardiac dysfunction — elevated left-atrial pressures cause pulmonary congestion; right-sided dysfunction causes systemic venous congestion.
Mismatch between effort and result — the central perception of dyspnea integrates afferent input from chemoreceptors, mechanoreceptors, and motor command, producing the subjective sensation.

Evaluation

History — onset, position dependence, smoking, exposures, exercise tolerance, leg swelling, syncope, hemoptysis, fevers.
Vital signs and oxygen saturation — tachypnea, hypoxia, hypotension, hypercapnia.
Focused exam — lung sounds (crackles, wheeze, decreased), JVD, edema, accessory muscle use.
ECG — arrhythmia, ischemia, right-heart strain.
Chest X-ray — pneumonia, edema, effusion, pneumothorax, cardiomegaly.
BNP / NT-proBNP — helps separate cardiac from non-cardiac dyspnea.
D-dimer — in low-pretest-probability patients to rule out PE.
CT pulmonary angiogram — for suspected PE; HRCT for ILD.
Echocardiogram — left and right ventricular function, valves, pulmonary pressures.
Pulmonary function tests — spirometry, lung volumes, diffusing capacity for chronic dyspnea.
Cardiopulmonary exercise testing (CPET) — for unexplained dyspnea after baseline workup.
Sleep study — for OSA and obesity hypoventilation.

Management

Treat the underlying cause — this is the cornerstone; everything else is supportive.
Acute heart failure — loop diuretics, oxygen, vasodilators (nitrates), non-invasive ventilation in severe pulmonary edema.
Asthma exacerbation — albuterol, ipratropium, systemic corticosteroids, oxygen.
COPD exacerbation — bronchodilators, corticosteroids, antibiotics, oxygen, NIV.
Pulmonary embolism — anticoagulation; thrombolysis or thrombectomy in massive PE.
Pneumonia — antibiotics, supportive care, oxygen.
ILD — antifibrotics (nintedanib, pirfenidone for IPF), pulmonary rehabilitation, oxygen, lung transplant in selected.
Anemia — iron repletion, treat underlying cause.
Pulmonary rehabilitation — effective in most chronic dyspnea.
Symptomatic dyspnea — opioids in advanced disease (palliative); fan therapy; breathing-control techniques.

When to Seek Medical Care

Severe sudden dyspnea, blue lips, or unable to speak full sentences — call 911.
Dyspnea with chest pain, syncope, or unilateral leg swelling (suspect PE).
Dyspnea with fever and productive cough (suspect pneumonia).
Orthopnea or PND in someone with known or suspected heart disease.
Hemoptysis, especially in smokers or with recent immobility.
Progressive exertional dyspnea over weeks to months.
Dyspnea in a pregnant woman, postpartum, or postoperative patient (PE risk).
Wheeze that does not respond to a rescue inhaler.

Connections

References & Research

Historical Background

The systematic taxonomy of dyspnea began with William Harvey's 17th-century circulation work and was refined by 20th-century physiologists. The MRC dyspnea scale (1959) and the Borg scale (1982) standardized symptom reporting; cardiopulmonary exercise testing in the 1980s let clinicians separate ventilatory, cardiac, and gas-exchange limitations.