Basic Life Support or BLS care is deemed when Primary Care Paramedics (PCP) only provide EMS response. Where limited ALS is available, BLS paramedics may provide first response to a trauma scene with or without ALS backup. EMS systems have evolved novel strategies to utilize ALS care. Some have mixed crew configurations with an ACP and PCP working on an ambulance. Some systems utilize an ACP on a roving vehicle which back up BLS practitioners when needed. EMS systems find solutions to meet the evolving standards of out-of-hospital care with the levels of practitioner available in their system.

The first responder is often the first on scene during trauma. This is often provided by full-time or volunteer firefighters as part of an integrated dispatch process. There are a few models around North America where police have adopted the first responder role. Regardless, within the public safety model, outside community agencies will work closely with EMS to provide care at the scene of a traumatized patient. First responders provide the extra hands, scene control, rescue, and extrication skills required in a busy trauma scene.