Dyspnoea

Overview

Dyspnoea is the feeling of breathlessness that is excessive for a given situation, sometimes with associated chest tightness. The most common cause is airflow obstruction secondary to asthma or COPD; other causes include obesity, functional hyperventilation, and long COVID/post-COVID syndrome (persistent breathlessness beyond the acute phase of COVID-19, particularly where initial cardiorespiratory workup is unremarkable — see COVID-19 & Post-COVID-19 Condition).

Broad categories:

• Respiratory: COPD, asthma, ILD, pleural effusion, malignancy, bronchiectasis, chest wall deformity, upper airway obstruction
• Cardiac: HFpEF, HFrEF, IHD, arrhythmias, valvular heart disease, pericardial disease
• Obesity/deconditioning
• Anxiety/hyperventilation
• Anaemia — unlikely to be the sole cause if Hb >110 g/L, unless a rapid drop or other contributing factors
• Other: thyroid disease, metabolic acidosis (e.g. DKA), neuromuscular disorders

Differentiating lung vs heart disease

Lung disease	Heart disease
History of respiratory disease	History of hypertension, IHD or valvular disease
Slow development	Rapid development
Present at rest	Mainly on exertion
Productive cough common	Cough uncommon, and then dry
Aggravated by respiratory infection	Usually unaffected by respiratory infection

Breathlessness at rest is common in respiratory causes (e.g. asthma) but uncommon except in advanced cardiac disease.

Asthma vs COPD

	Asthma	COPD
Symptoms <35yrs	Common	Unusual
Smoking history	Possible	Invariable
Chronic cough	Uncommon	Common
Dyspnoea pattern	Diurnal and variable	Constant and progressive
Response to bronchodilator	Good	Poor
Nocturnal waking	Common	Uncommon
Airflow obstruction	Reversible	Non-reversible

Red flags

Advanced age, sudden symptom onset, known IHD, recent migrant from Africa/Asia (TB), unexplained weight loss, haemoptysis, trauma, HIV, pallor/cyanosis, dyspnoea at rest, calf tenderness (DVT/PE — see Pulmonary Embolism for the canonical page on this topic, and DVT — Investigation for the leg side of it).

History and examination

Presence of wheeze is very informative; most respiratory causes are associated with cough. Time course is also useful — sudden onset suggests PE/pneumothorax; onset over 1–2 hours suggests LVF/asthma.

Crackles on examination: fine crackles (infection/pneumonia or fibrosis); medium crackles (CCF); coarse crackles (airway mucus — usually clears with coughing).

Investigations

Chest X-ray; pulmonary function testing (spirometry initially).

By age group

Children: asthma, bronchiolitis, pneumonia/other infections are the common causes. Don’t miss: epiglottitis, croup, myocarditis. Sudden dyspnoea: inhaled foreign body, pneumothorax.

Elderly: most commonly LVF and COPD.