Definitions for EMS Event Intervals
| EMS Event Interval | Decision Rule |
|---|---|
| Discovery interval | Estimated time last seen to time EMS notified (dispatch called) |
| Call-response interval | Time EMS unit notified (dispatch called) to time of BLS or ALS arrival at scene |
| Scene-interval | Time of BLS or ALS arrival at scene to time EMS unit left scene |
| Minutes to CPR | If the arrest is witnessed and with bystander CPR or the arrest occurs in the presence of EMS, then minutes to CPR = 0 |
| If arrest is witnessed and without bystander CPR, minutes to CPR = time EMS unit notified (dispatch called) to time BLS or ALS arrived at scene | |
| If arrest is unwitnessed and without bystander CPR, minutes to CPR = estimated time last seen to arrival of BLS or ALS at scene | |
| If arrest is unwitnessed and with bystander CPR on discovery, minutes to CPR = time patient last seen to time EMS unit notified (dispatch called) | |
| Start-stop CPR interval | If bystander CPR present, start-stop CPR interval = the time EMS unit notified (dispatch called) to time of ROSC or death |
| If patient arrested in presence of EMS providers or there is no bystander CPR, start-stop CPR interval = time of EMS unit arrival to time of ROSC or death | |
| Transport interval | Time EMS unit left scene to time of arrival in ED |
| Sustained ROSC | If known ROSC >20 min or ROSC in the field or in the ED that results in the patient being admitted to the hospital alive |
BLS, indicates basic life support; ALS, advanced life support.