Breathing can be difficult for anyone in Colorado. I lived in Denver for close to a year, and I can see it would be very difficult for anyone with emphysema to breath let alone sing.

Willie Nelson was supposed to play at a fundraiser in Castle Pines, Colo., on Saturday. But the 79-year-old singer had to cancel.

USA Today said that organizers told the audience Nelson was suffering “from breathing problems due to the high altitude and emphysema” and was taken to a nearby hospital.

“I was told Willie woke up and had trouble breathing, so he was taken to the hospital,” fundraiser host Fred Bartlit told the Denver Post.

Nelson is scheduled to perform at the House of Blues in Dallas on Tuesday.