Lady Gaga had to get emergency care in Colorado due to the altitude, but she was well enough to take a selfie while she wore an oxygen mask.

 

A lot of artists struggle with shows in high altitudes if they aren't prepared. In 2013, Carrie Underwood took a photo of herself huffing oxygen while in Colorado. In 2012, Tracy Morgan was in Utah when he fainted after giving an acceptance speech at the Sundance Film Festival.

 

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