Table 2 Participant exclusion criteria (published in protocol paper [17])

Lay public 999 callers

Calls were excluded where: (i) 999 caller was not at the scene; (ii) 999 call originated from a landline; (iii) 999 call originated from another emergency service e.g. police or fire; (iv) 999 calls where resource (excluding community first responder) would arrive on scene before video livestreaming could be activated; (v) 999 call ended before transfer for activation of video livestreaming; (vi) 999 calls where another incident took priority; and (vii) calls where clinical acuity was found to be lower than the threshold for the study (not major trauma)

All callers identified by the dispatchers as a child caller (under 16 years old) and those who selected they are under 16 on the 999-caller survey were excluded

All callers identified by the HEMS dispatchers/APP-CCs as a child caller (under 16 years old) and those who selected they are under 16 on the 999-caller survey were excluded

N/A

EOC staff

EOC staff not mentioned in the inclusion criteria

EOC staff not mentioned in the inclusion criteria

EOC staff not mentioned in the inclusion criteria

Trauma patients

Any emergencies of a suspected medical origin (e.g., heart attack or stroke)

Any emergencies of a suspected medical origin (e.g., heart attack or stroke)

N/A