Joan Rivers Joan Rivers

Could Joan Rivers' death have been prevented?

Rivers may have stopped breathing during an unscheduled throat biopsy that cut off her air supply, according to a damning report in the New York Daily News.

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Rivers never regained consciousness after she was rushed to a Manhattan hospital on Aug. 28, when she stopped breathing during a routine surgery on her vocal cords. She died Sept. 4 at the age of 81.

A medical source told the Daily News that during the procedure at Yorkville Endoscopy, a doctor at the clinic noticed "something" on the comedienne's vocal cords. Rivers' personal doctor, who had accompanied the Fashion Police host to the clinic and whom the Daily News does not name, then asked if he could use the clinic's instruments to perform an impromptu biopsy — a procedure Rivers hadn't signed off on, according to the paper. The comedienne's vocal cords seized during the biopsy and cut off her air supply.

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"A biopsy like that should only be done in a hospital setting," the source told the Daily News. "If she had been in a hospital when it happened, she might have been okay."

According to the New York Times, Rivers' personal physician is Dr. Lawrence B. Cohen, a gastroenterologist. He wrote a 2007 paper for the medical journal Gastroenterology, in which he made the controversial argument that gastroenterologists should be able to perform endoscopies on otherwise healthy patients without an anesthesiologist present.

Rivers had reportedly signed off on an endoscopy, but not a biopsy, before going to the clinic.

An autopsy on Rivers was inconclusive and more tests are being conducted to determine her cause of death.