Acute Shortness of Breath

This is a terrifying symptom for the patient, and the subjective feeling of shortness of breath is not predictably related to the type or degree of pathology. This, combined with the fact that the cause is often organic, means that a careful and urgent assessment and appropriate referral is mandatory.

Published: 2nd August 2022 | Updated: 3rd February 2023

Differential diagnosis

Common Diagnoses

Asthma
Pneumonia
Acute LVF
Acute Exacerbation of COPD
Hyperventilation

Occasional Diagnoses

Pneumothorax
Pulmonary Embolism
Pleural Effusion
Diabetic Ketoacidosis (DKA)
Lobar Collapse (Tumour)

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

	Asthma	Pneumonia	LVF	Exacerbation of COPD	Hyperventilation
Purulent Phlegm	Possible	Yes	No	Yes	No
Coarse Crackles	No	Yes	No	Yes	No
Bilateral Wheeze	Yes	No	Possible	Yes	No
Bilateral Fine Crackles	No	No	Yes	Possible	No
Focal Reduced Air Entry	No	Yes	No	No	No

Possible investigations

The GP is highly unlikely to initiate any investigations at all. 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 see them.
Spacer devices are considered first line when managing acute exacerbations of asthma – both in and out of the surgery setting.
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.