A mom has recalled a difficult conversation she had with a doctor after her teenage daughter fell unwell with 'popcorn lung'.

Christie Martin received a panicked call from her daughter Brianne Cullen who claimed she was struggling to breathe.

Horrified, Christie rushed the 17-year-old to a nearby ER where she was given oxygen, X-rays and medication before being diagnosed with bronchiolitis obliterans — a health condition better known as 'popcorn lung'.

It's an uncommon type of lung disease caused by a build-up of scar tissue in the lungs, which blocks the flow of air.

Little did Christie know that Brianne had started secretly vaping at the age of 14.

Recounting the day her daughter started to feel sick, Christie, from Henderson, Nevada, US, said: "[Brianne] went to cheer sick, she had a cough and a sore throat. She was lifting up these kids, tumbling, it's all very straining.

"She called me all of a sudden and said she can't catch her breath.

"I couldn't understand her, she kept saying 'I can't breathe', it was the scariest thing."

The mom went on to credit the sport for saving Brianne's life.

"Cheer saved her life because the exertion that you put out during cheer practice on top of being sick, she couldn't breathe," Christie said.

"The doctor came in and said, we need to have a very serious conversation," the mom went on to recall of their hospital dash.

"I didn't expect the news she gave me, that it was popcorn lungs that's permanent and children are dying from it. [...] We still don't know if there will be long term effects."

Brianne, who puffed on a $25 vape she bought each month for three years, was given an inhaler by doctors at St. Rose Dominican Hospital to help her breathing.

Christie said: "We don't know the status of her lungs now, I was an absolute mess at the ER that night.

"They told me she should be able to make a full recovery because we caught it so early, but it can also cause problems like cancer in the future. I thought I failed as a mother.

"Smoking takes years to show its effect and your lungs can heal from it, but popcorn lung is irreversible."