Pulmonary embolism is indicated by breathing rate increases by a factor of two.
 In those who have low risk, age less than 50, heart rate less than 100 beats per minute, oxygen level more than 94% on room air, and no leg swelling, coughing up of blood, surgery or trauma in the last four weeks, previous blood clots, or estrogen use, further testing is not typically needed
 shortly after a major operation), or a person has a pulmonary embolus in spite of being anticoagulated

