David Keys tried desperately to save the life of teenage horse rider Olivia Inglis but was essentially helpless without crucial equipment, a Sydney inquest has heard.
Seventeen-year-old Olivia was fatally crushed when she and her horse tumbled over a jump at the Scone Horse Trials in March 2016.
Mr Keys told the NSW Coroners Court on Friday that on the day of Olivia's death he'd been hired to provide "general first aid" by private contractor Health Services International.
Mr Keys said he had raised the issue of needing better equipment and more advanced medical professionals at events with his employer in the weeks before the fatal fall, but had been told it was "cost prohibitive".
"No one would pay for that," he said he was told.
Mr Keys arrived by Olivia's side about one minute after a call came through that a rider had fallen. He immediately tried to clear Olivia's airways but his machine lost suction.
Olivia suffered tension pneumothorax which was displacing her internal organs.
It's something Mr Keys - as a former combat medic with the army reserve and trained physician assistant - said he and the doctor who arrived later could have begun to work on.
But there was neither a cannula long enough nor an advanced airway kit inside his ambulance.
"I was extremely frustrated," Mr Keys said.
"Especially knowing how serious and how quickly it could turn bad."
Olivia died at the scene.
Her death came just weeks before 19-year-old equestrian Caitlyn Fischer was similarly killed during an April 2016 eventing competition in Sydney.
Deputy state coroner Derek Lee is examining the circumstances surrounding both tragedies in a two-week inquest at the coroners court at Lidcombe.
Counsel assisting Peggy Dwyer on Friday asked Mr Keys what he thought of Equestrian Australia's new requirement that paramedics with the capacity to provide advanced life support be present at events.
"It's a very good move, a good step forward," he said.
After his evidence, Mr Keys made an emotional speech to the parents of the girl he couldn't save.
"If I could just express my condolences to the families. I know what a painful time you are going through and I hope the changes made here can give you some resolve and help you move forward," he said.