Key Points
- Alarm signs requiring immediate assessment: confusion, marked cyanosis, dyspnoea while speaking (inability to speak in full sentences), and insufficient respiratory effort or respiratory exhaustion
- Red flag symptoms patients should seek urgent care for: rapidly worsening dyspnoea, chest pain, syncope, haemoptysis, and peripheral oedema
- Critical vital sign thresholds: HR >120 bpm, RR >30/min, SpO₂ <90%, accessory muscle use, altered mental status, stridor, or cyanosis
- Red flags per NHS England pathway: chest pain, haemoptysis, cyanosis, inability to speak in sentences, confusion, agitation, unilateral leg swelling, stridor, increased VTE risk, rapidly progressing symptoms, new low resting SpO₂, or unexplained reduction in SpO₂ with elevated RR
Red Flag Symptoms
These should prompt urgent evaluation for potentially life-threatening causes (PE, ACS, pneumothorax, acute heart failure, anaphylaxis):
- Chest pain (particularly cardiac-sounding pain at rest)
- Haemoptysis
- Syncope or presyncope
- New or worsening peripheral oedema
- Unilateral leg swelling (raises concern for DVT/PE)
- Rapidly worsening or sudden-onset dyspnoea
Red Flag Signs on Assessment
- Inability to speak in full sentences
- Confusion, agitation, or altered mental status
- Cyanosis (lips, nail beds, skin)
- Accessory muscle use / intercostal or subcostal retractions
- Stridor (inspiratory and/or expiratory)
- Insufficient respiratory effort or respiratory exhaustion
- Tripod positioning
Critical Vital Sign Thresholds
| Parameter | Threshold |
|---|---|
| Heart rate | >120 bpm (or <60 bpm) |
| Respiratory rate | >30/min |
| SpO₂ | <90% (or <92% if COPD, per Qld Health) |
| Systolic BP | <90 mmHg |
| New low resting SpO₂ or reduction on minimal exercise | Unexplained |
Key Life-Threatening Causes to Exclude
Acute-onset dyspnoea within minutes to hours should raise concern for: acute coronary syndrome, pulmonary embolism, pneumothorax, acute asthma/bronchospasm, anaphylaxis, or foreign body aspiration. Subacute onset over days to weeks may suggest heart failure, pneumonia, or anaemia.
See sources cited
- The Differential Diagnosis of Dyspnea (09.12.2016)
- Dyspnea - StatPearls - NCBI Bookshelf - NIH
- NHS England » Adult breathlessness pathway (pre-diagnosis): diagnostic pathway support tool
- Clinical Practice Guidelines for the Diagnosis and Management of Dyspnea in Primary Care and Outpatient Setting - journal.pafp.org
- Differentiating causes of Dyspnea in emergency and its management - J Otorhinolaryngol Allied Sci
- [PDF] Rotherham Adult Breathlessness Assessment Algorithm
- [PDF] 3 Emergency - Queensland Health
- Dyspnea in the Urgent Care: Differentiating Benign From ‘Can’t Miss’ - Journal of Urgent Care Medicine Dyspnea
Evidence Validator
Heidi Clinical Team4 Contributions
Dr. Sasha Sadiq
Primary Care / Emergency Medicine•AU
