Denver left Lady Gaga breathless - literally.

After wrapping up her concert in Denver on Wednesday night, the 28-year old "Artpop" singer fell ill due to altitude sickness. She was rushed to a local hospital.

While in the hospital, the singer snapped a photo of herself fully made up, with fake eyelashes to boot, wearing an oxygen mask. Apparently, an illness isn't an excuse to look sick.

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The Grammy-award winning singer, known for her wild props and out-of-this-world outfits, seems to have found a new accessory, as she uploaded the photo on Instagram and captioned it with "Altitude Sickness is no Joke! #hitThatHospitalS--t  #artRaveDenver many true ravers crowd tonight."

Her sickness certainly isn't a joke. Altitude or Mountain sickness is caused by exposure to low oxygen and high altitude, which leads to flu-like symptoms or a feeling that resembles carbon monoxide poisoning.

Although the sickness is "no joke", a possible oxygen mask selfie trend might just be.

However, if Lady Gaga's oxygen mask selfie becomes a trend, it wouldn't come as a surprise to many. The singer has been known to start odd cultural trends anyway.

She once said that clothes are as integral to her performance onstage as the music she sings. Onstage or off-stage, Lady Gaga said that she wants to be able to tell a story, saying that the image she wants to portray should be so strong that her fans will "want to eat and taste and lick every part."

"It's all about everything altogether-performance art, pop performance art, fashion," she added.

Lady Gaga's stint in Denver is part of her "The ARTPOP Ball" world tour.

Despite the illness, the show must go on. She is scheduled to perform again on Friday in Seattle.

Aside from Lady Gaga, other performers also fell ill during their concert tours recently, for one reason or another. The list includes Morrissey, Paul McCartney and Miley Cyrus.

TagsLady Gaga, sick, altitude sickness, oxygen mask, Denver