Sisters Felicity and Lucy Scrivener share a fear of heights. But the pair also share a deep affection for their 75-year-old grandmother, who is gravely ill with the lung disease emphysema.

They are preparing to overcome their own terrors to raise awareness of the progressive condition, which causes the small air sacs in the lungs to dilate, and is irreversible.

On June 15, 20-year-old Lucy, from Colchester, will undertake a bungee jump from 160ft. Then the following day, Felicity, 22, will take to the skies and parachute jump from 13,000ft over Chatteris airfield.

Felicity, who lives in Sudbury, said: “Our nan has been hospitalised for more than three months - she suffered a cardiac arrest on Valentine’s Day after having emphysema for 18 years.

“We see our nan as an inspiration for continuing to fight this disease and we get so choked up talking about the difficulties she has faced. Climbing one step to her is the equivalent of us climbing Mount Kilimanjaro.”

The girls have decided not to watch helplessly while their beloved nan fights for her life, and they have pledged to do something to help find a cure for emphysema.

Felicity continued: “We also want to raise awareness of emphysema as not many people of our generation have ever heard of this disease. There are so many smoking campaigns that warn about lung cancer, but if people realised emphysema can occur years after quitting smoking, they might think twice about starting. Our Nan stopped smoking before we were born but the damage had already been done.

“We really want the public to listen to our story and if we can get just one person to stop smoking because of our plight - or help research into a new cure to save just one life - then we know that overcoming our fears to undertake these challenges will be worthwhile.” The sisters have raised £700 so far and hope to hit a £1000 target. Visit http://www.justgiving.com/Sisters-LeapOfFaith to donate.