Denver, Colorado - Rapper Cardi B shared a shocking backstage clip from her sold-out concert in Denver. Apparently, she needed emergency oxygen!

"B**ch this air ain't no joke," Cardi B wrote in the caption of a video in her Instagram Stories late Monday night.

The clip shows the WAP rapper sucking down emergency oxygen backstage at her concert at the Ball Arena in Denver, Colorado.

Panting she yells, "Denver! Denver is f**king different," before adding a "Wooo."

Denver is also known as the Mile High City due to its official elevation of exactly a mile.

The altitude can make breathing harder for some people, especially those not acclimated to the elevation, as the air is thinner.

Performing at higher elevations could be especially tricky for people with asthma – like Cardi B.

While preparing for The Little Miss Drama Tour, the 33-year-old rapper openly discussed her asthma in an interview with Billboard, saying, "I have asthma. My fans know I got asthma. They know I gotta take a water break. But, I’m going to give it my all."

As Cardi's Instagram Stories show, she's doing just that. Monday's concert was her 14th consecutive sold-out show.