Ollie Rosenwould, 17, experienced a life-threatening arrest at home in May after feeling unwell at school earlier that day.
His mother Donna said: “It was awful.
“Before I knew it, our house was full of paramedics and I could hear the air ambulance flying overhead.
“The paramedics took me out of the room to make space for them to begin chest compressions.”
Ollie, who has a connective tissue disorder and was still recovering from recent chest surgery, suffered a tension pneumothorax.
This means a collapsed lung caused by trapped air putting pressure on the heart and blood vessels.
The severity of the situation became clear when he told his mother: “Mum, I need an ambulance.”
He soon stopped breathing and went into cardiac arrest.
Paramedics performed a rare emergency procedure, needle decompression, which involves inserting a needle into the chest wall to release trapped air.
Donna said: “I then heard the sound of the defibrillator and didn’t think Ollie was going to make it.
“Paramedics saved his life.
“I keep replaying it in my head but thank God the ambulance crews were there.
“I dread to think what would happen if Ollie didn’t ask for an ambulance.”
Ollie was taken to St Bartholomew’s Hospital for specialist surgery to fix the air leak in his lung.
During the chaotic scene, Donna recalled a moment of compassion from one of the paramedics.
She said: “While he was being loaded onto the ambulance, one of the paramedics pulled me to one side and hugged me.
“She wanted to hug me – one mum to another.
“That got me through some tough times being strong for my boy.”
Following his recovery, Ollie asked London Ambulance Service to visit his school, Jo Richardson School in Dagenham, to train his classmates in CPR and other life-saving skills.
He was reunited with the crew who helped save his life.
Paramedic Daisy Page said: “It was great seeing Ollie look so well and helping to teach his friends how to do CPR.
“Last time we saw him he was so poorly and we don’t often meet our patients afterwards, so it was really nice meeting him.”
Ollie described the reunion as long overdue.
He said: “I’ve been wanting to meet the crews for a while and it was really great to see them.
“CPR training should be taught at schools everywhere – it’s so important.
“I’m living proof that cardiac arrest can happen to anyone or someone you know.”
