Acute Shortness of Breath

Differential Diagnosis

Common Diagnoses

Occasional Diagnoses

Rare Diagnoses

  • Aspiration Pneumonitis
  • Guillain-Barré syndrome
  • Hypovolaemic Shock
  • Shock Lung (Adult Respiratory Distress Syndrome)
  • Laryngeal Obstruction

Ready Reckoner

Key distinguishing features of the most common diagnoses

AsthmaPneumoniaLVFExacerbation of COPDHyperventilation
Purulent Phlegm PossibleYes NoYes No
Coarse Crackles NoYes NoYes No
Bilateral WheezeYes No PossibleYes No
Bilateral Fine Crackles No NoYes Possible No
Focal Reduced Air Entry NoYes No No No

Possible Investigations

  • The GP is highly unlikely to initiate any investigations at all other than pulse oximetry to assess oxygen saturation. If the patient with acute shortness of breath is ill enough – or the diagnosis obscure enough – to warrant investigation, then the patient probably requires admission. The following therefore refers to those few cases in which the patient is reasonably well, the diagnosis unclear and the scenario not so urgent that immediate referral is required.
  • Urinalysis: Glucose and ketones in DKA. Confirm with a glucometer reading.
  • Sputum culture: Very occasionally helpful in infective processes not settling with first-line empirical treatment.
  • FBC: WCC raised in infection. Anaemia may be significant incidental finding.
  • Pulse oximetry: Hypoxia suggests a significant problem.
  • CXR an essential part of assessment but usually done after admission/referral.
  • Other investigations such as blood gases and investigations for pulmonary embolus might be required to clinch a diagnosis but would be arranged by the admitting team.

Top Tips

  • If the diagnosis is likely to be hyperventilation, instruct the patient to rebreathe from a paper bag while waiting for you. This action may curtail the attack by the time you arrive.
  • Spacer devices can be as effective as nebulisers when managing acute exacerbations of asthma, and are more practical to use when on call.
  • Sudden onset of breathlessness in an elderly patient in the middle of the night is likely to be LVF. Remember that it may be have been precipitated by an infarct.

Red Flags

  • Cyanosis is an ominous sign meriting a ‘blue light’ ambulance and oxygen as soon as possible.
  • The presence of intercostal recession and use of accessory muscles of respiration indicate severe respiratory distress whatever the aetiology. Admit.
  • If a foreign body has been inhaled, astute telephone assessment and clear, calm advice may be lifesaving.
  • Acute confusion with breathlessness indicates severe hypoxaemia, metabolic disturbance or sepsis. Admit urgently.
  • Don’t forget that pneumothorax is commoner in asthmatics and patients with COPD – consider this diagnosis if the patient suddenly becomes more short of breath especially if there is no other obvious explanation, such as a supervening chest infection.
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