<keypoints>
- **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
</keypoints>
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)