During a Colorado concert last week Carrie required oxygenbecause the venue's high altitude bothered her.
She performed in Broomfield on Thursday, but before her encore she returned to her dressing room where she posted a photograph of herself wearing an oxygen mask on Twitter. Carrie wrote, "In high altitudes, they put oxygen in my dressing room under the stage! This is me before the encore."
She later added: "Thanks, Colorado, for the wonderful energy over the last two shows! I can always tell when I'm in a great place full of great people."