Cave, 25, was admitted to the intensive care unit at Sunnybrook Hospital in Toronto.
“Please keep Colby and his wife Emily in your thoughts and prayers right now,” the Oilers said in a tweet.
Cave, originally from Battleford, Saskatchewan, has not been drafted. He signed an entry-level deal with the Boston Bruins in 2015. Cave was claimed by the Oilers for waivers in 2019. He has played 11 games with the Oilers this season, as well as 44 games with the Bakersfield Condors of the AHL. Cave has participated in 67 NHL games over the course of his career with the Oilers and Bruins.