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Probability diagnosis

Bronchial asthma

Bronchiolitis (children)


Ageing, lack of fitness

Left heart failure/CCF


Serious disorders not to be missed


  • acute heart failure (e.g. AMI)

  • acute coronary syndromes

  • arrhythmia

  • pulmonary embolism

  • pulmonary hypertension

  • dissecting aneurysm

  • cardiomyopathy

  • pericardial tamponade

  • anaphylaxis


  • bronchial carcinoma, other malignancy


  • SARS

  • avian influenza

  • pneumonia

  • acute epiglottitis (children)

Respiratory disorders:

  • inhaled foreign body

  • upper airways obstruction

  • pneumothorax

  • atelectasis

  • pleural effusion

  • tuberculosis

  • acute respiratory distress syndrome (ARDS)

Neuromuscular disease:

  • infective polyneuritis (Guillain-Barré)

  • poliomyelitis

Pitfalls (often missed)

Interstitial lung diseases:

  • idiopathic pulmonary fibrosis

  • extrinsic allergic alveolitis

  • sarcoidosis

  • drug-induced interstitial lung disease

Chemical pneumonitis

Metabolic acidosis


Kidney failure (uraemia)

Multiple small pulmonary emboli

Masquerades checklist



Drugs (see list)


Thyroid disorder (thyrotoxicosis)

Is the patient trying to tell me something?

Consider functional hyperventilation (anxiety and panic attacks).

Key history

Aim to differentiate between pulmonary causes such as COPD and asthma and cardiac failure. Assess the rate of development of dyspnoea.

Key examination

  • Careful inspection is mandatory. With patient stripped to waist observe for factors such as cyanosis, clubbing, mental alertness, dyspnoea at rest, use of accessory muscles and rib retraction

  • Use auscultation to differentiate between crackles and wheezes

Key investigations

The two most important are CXR and pulmonary function test including pulse oximetry. Others include:


  • arterial blood gases

  • cardiology (e.g. ECG, echocardiography, enzymes and other medical imaging).

Diagnostic tips

  • All heart diseases have dyspnoea on exertion as a common early symptom.

  • Several drugs can produce a wide variety of respiratory disorders especially pulmonary fibrosis and pulmonary eosinophilia. The main agents are amiodarone and cytotoxic drugs.

  • The abrupt onset of severe dyspnoea suggests pneumothorax or pulmonary embolism.

  • Toxic agents that may cause hyperventilation are salicylate, methyl alcohol, theophylline overdosage and ethylene glycol.

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