Which of the following cases would allow EMS to initiate care?

Initiating care in the context of EMS protocols is largely governed by the immediacy of a patient's condition and the presence of critical events that require intervention. A witnessed arrest by EMS personnel is a clear situation where immediate action is necessary. In this scenario, paramedics or EMTs are present and able to observe a patient suddenly become unresponsive and cease breathing or have no pulse. This provides a direct legal and ethical basis for initiating life-saving measures such as CPR and advanced cardiac life support (ACLS) without needing further consent or confirmation from others, as the need for urgent care is evident.

This contrasts with the other scenarios, which do not present an immediate medical emergency. Delayed patient registration could indicate a lack of urgency in starting care, as it pertains more to administrative processes rather than immediate medical response. Allergic reactions reported by family might warrant care, but without a direct assessment, the severity and need for immediate intervention depend on the presentation of the patient, which is less clear. Finally, non-traumatic conditions without symptoms suggest that the patient is stable or asymptomatic, and therefore, there is no imminent need for EMS to intervene at that moment. In summary, the urgency and clarity of the emergency situation presented in a witnessed arrest justifies