Lady Gaga asked for oxygen to calm her down before her performance at The O2 in London at the weekend.
The 'Do What U Want' singer had St John Ambulance first aid crew bring her a cylinder of oxygen as she prepared to hit the stage at Capital FM's Jingle Bell Ball on Sunday (08.12.13).
A source told the Daily Mirror newspaper: "Gaga had oxygen with her during her last tour, and it's become something she now relies on in work situations.
"It had originally been overlooked in her rider so a crew from St John Ambulance were sent out to set up an oxygen canister for her ... Gaga has had a really rough year and genuinely sees it as an essential medical supply. Neat oxygen gives her energy and calms her down."
In the past year the 27-year-old pop star has undergone hip surgery, which saw her spend time in a wheelchair.
Gaga also parted ways with her long-term manager, Troy Carter, while her album 'ARTPOP' has not had the same sales success as her previous release 'Born This Way'.
The 27-year-old singer arrived on stage late at the Jingle Bell Ball after struggled to walk in her 12-inch platform heels from her dressing room to the piano.
Gaga did meet the Beckhams backstage and chatted to Victoria, David and their four children, and even signed an autograph for them after fashion designer Victoria asked.
The musician was seen "cuddling" their daughter Harper and got on well with the superstar couple.
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