CHICAGO (CBS) — Next month, more than 4,000 people will climb 94 floors all the way to the top of the John Hancock Center to raise money for breathing problems, and one man knows what it’s like to gasp for air.

As CBS 2’s Susan Carlson reports, Steve Ferkau is getting ready for his 10th climb this year, and he proves the sky is truly the limit.

“I have cystic fibrosis,” Ferkau said. “It’s a genetic disease that I was born with.”

Ferkau struggled to breathe until he had a double lung transplant in 2000. Despite his challenges, for the past nine years he’s managed to reach the top at the Hustle up the Hancock.

But he’s not in it for the notoriety, or even the fact that he’s raised more $250,000 for the Respiratory Health Association.

“I’ve always done this to tell people about Kari,” Ferkau said.

Kari Westberg is the 17-year-old girl whose lungs Ferkau now uses to breathe. The day before her junior prom, the Iowa girl died of an aneurysm.

“In my heart, they’ll always be her lungs and they’ll always be her gift, but I lived for 40 years without understanding what it felt like to breathe normally,” Ferkau said. “I never imagined it would feel this amazing.

What is also amazing is the bond that’s developed over the past decade between Ferkau and Kari’s friends and family.

“Twelve years after she passed away, they still come out and honor her by climbing with me,” Ferkau said. “This year, it’s my 10th climb and I have 20 of them coming out.”

Another regular on Ferkau’s team is his wife of 23 years, Laura. She, too, holds Kari’s family in high esteem.

“Her family just has a special kind of grace, that they would think of others at such a horrible time in their lives,” Laura Ferkau said. “I’m so grateful to them.”

Ferkau says he feels like Kari is with him all the time.

“It’s always like there’s a guardian angel over my shoulder,” he said.

In the month before Kari died, she told her family twice how strongly she felt about organ donation. When tragedy struck, her family had no doubt about her wishes.

If you would like to participate in the Hustle up the Hancock, there are still spots available for the half-climb. Click here for more from the Respiratory Health Association of Metropolitan Chicago.