Dawn Sturgess was in “non-survivable” condition when paramedics arrived at the scene, a medical expert has told an inquest looking into her fatal Novichok poisoning.

The 44-year-old died on 8 July 2018 after being exposed to the nerve agent, which was left in a discarded perfume bottle in Amesbury, Wiltshire.

Her death followed the attempted murders of ex-spy Sergei Skripal, his daughter Yulia and then-police officer Nick Bailey, who were poisoned in nearby Salisbury in March 2018.

All three survived, as did Ms Sturgess’s boyfriend Charlie Rowley, who unwittingly gave her the bottle containing the deadly nerve agent.

The inquest in central London heard that Ms Sturgess’ cause of death was hypoxic-ischemic brain injury following cardio-respiratory arrest caused by Novichok nerve agent poisoning.

Hypoxia in the brain is caused by lack of oxygen and ischemia by lack of blood flow.

Dr Jasmeet Soar, who works in intensive care medicine and is a consultant at Southmead Hospital in Bristol, explained that the effects of Novichok, if not treated “quickly”, can lead to a “vicious cycle of muscles becoming weaker”. including the muscles in the chest and diaphragm which are the mechanisms by which we breathe.

After this period of time, even if you can restart someone’s heart, you will not survive cardiac arrest due to irreversible hypoxic-ischemic brain injury

He said not being able to breathe leads to low oxygen levels in the blood and brain, which can lead to unconsciousness and eventually cardiac arrest.

Once the heart stops beating, the brain is deprived of oxygen and “dies very slowly,” the doctor continued.

He and another medical expert, Professor Jerry Nolan, testified on Wednesday and estimated that Ms Sturgess did not receive CPR treatment for almost 10 minutes after her cardiac arrest.

Prof Nolan, a consultant in anesthesia and intensive care medicine, said: “After this period of time, even if you can restart someone’s heart, you will not survive cardiac arrest due to irreversible hypoxic-ischemic brain injury.”

He said in his opinion Ms Sturgess’ condition was already unsurvivable by the time paramedics attended.

Prof Nolan also agreed that whatever treatment he received from paramedics or hospital staff would not have made a difference if he survived.

In a report, the pair concluded that Ms Sturgess’ prolonged period of cardiac arrest caused severe irreversible hypoxic-ischemic brain damage and meant she would have died in hospital.

They also discovered that she had a brain hemorrhage during her intensive care stay, which was a complication of the brain injury.

Consultants wrote: “In our view, in her circumstances, she had no chance of surviving to leave hospital.

“We note that the decision to withdraw life-sustaining treatments was made based on her clinical circumstances and her family’s statement that Dawn Sturgess ‘would not want continued treatment in the face of significant brain damage.’ They feel that Dawn died at home last week.”

They also concluded that any real or perceived delay in starting treatments for Novichok poisoning did not affect Ms Sturgess’s survival and that the treatment she received at the scene and in hospital was of a reasonable standard.

Jesse Nicholls, asking questions on behalf of Ms Sturgess’s family, showed drafts of the inquiry’s documents being considered by the Department of Health into the risk of a secondary incident following previous poisonings in Salisbury.

He singled out one of the ways authorities believed a secondary incident could occur as “accidental discovery of an agent dropped by humans,” which he said was “unfortunately the worst-case scenario that’s reasonably horrendous that happened to Dawn Sturgess.”

Asked whether providing this information to clinicians could have been helpful, Professor Nolan said: “I can only say that it could have happened, but as I say, it’s speculation on my part.”

Dr Soar explained that Ms Sturgess was probably the only poisoning victim to go into cardiac arrest because she was likely exposed to a relatively high dose of Novichok compared to Mr Rowley and the Skripals.

He told the inquest that, according to Mr Rowley’s interviews, Ms Sturgess sprayed her perfume on her wrists while he spilled some on his hands, which he then washed.

“Unfortunately, she inadvertently applied it and sprayed herself on her wrists … as opposed to having accidental or more tactile contact with it,” Dr Soar said.

He also said he likely inhaled aerosol components of the agent.

The investigation continues Thursday.