Medical personnel were "frustrated" by the radio systems at a music festival where two people fell ill and died, an inquest has heard.
Tommy Cowan, 20, died in hospital after having a fit at the Mutiny Festival in Portsmouth in May.
An inquest in Portsmouth heard he showed signs of having taken MDMA and that his death was an accident.
Georgia Jones, 18, also died after collapsing earlier the same day at the event.
Giving evidence, Oliver Sharp, a first responder with the on-site medical team, said: "Multiple organisations were using radio channels with poor etiquette. It was very frustrating."
He said it meant there was a delay of up to two minutes in calling an ambulance for Mr Cowan, although this did not affect the care given to him.
He also said he was aware of "lots of drugs" being taken but did not know Georgina Jones had collapsed earlier in the day.
Forensic pathologist Dr Brett Lockyear said tests showed Mr Cowan had a "high level" of MDMA in his blood, but also showed signs of an allergic reaction, possibly to a substance the drug had been mixed with.
One witness said Mr Cowan had hidden the pills in his trousers.
But Mutiny's operations manager, Neil Roberts, told the inquest the festival's security measures were "gold standard".
"It's very difficult if someone wants to sneak something in that is as small as a paracetamol," he said.
Reaching a conclusion of accidental death, coroner David Horsely said Mr Cowan had "wild times, but was beginning to settle down".
He said: "He succumbed to temptation, he wasn't a drug addict. He inadvertently took something which has killed him. Taking illicit substances is like Russian roulette, you don't know what you are getting, it's strength and what's in it.
"All the security measures in the world aren't going to stamp this out."
After the hearing, Mr Cowan's mother, Brook Hoar, said she was campaigning for more free drug testing to be made available at festivals.
She said: "If we can just save one family from going through what we have, it will be worth it."
The festival at King George V playing fields was headlined by Dizzee Rascal.
The second day was cancelled, and a number of other people were taken to hospital with drug-related symptoms.
The coroner ruled Georgia Jones's death was accidental at her inquest on Tuesday.