Willie Nelson is back on the road after canceling a Saturday (Aug. 18) concert appearance near Denver. The 79-year-old singer-songwriter was hospitalized for altitude-related breathing problems and emphysema, according to Denver's NBC affiliate KUSA-TV. He was scheduled to perform a concert Saturday night in a private home in Castle Pines, Colo., to raise money for a local animal shelter. "He's fine," his publicist, Elaine Schock, told The New York Times on Monday (Aug. 20). "He's on the road to the next gig, and he's not in any danger." Nelson's next concert is scheduled for Tuesday (Aug. 21) at the House of Blues in Dallas.