Box 1.

Pulmonary embolism rule-out criteria

  • Age <50 years

  • Pulse <100 beats/minute

  • Arterial oxygen saturations >94% (on room air)

  • No unilateral leg swelling

  • No haemoptysis

  • No recent trauma or surgery

  • No prior venous thromboembolism event

  • No exogenous oestrogen use