A former nursing assistant at an East County rehabilitation center who admitted raping a 76-year-old incoherent patient in her room on multiple occasions was sentenced Friday to three years in prison.Felix Panem, 54, pleaded guilty in June to rape of an incoherent patient and elder abuse.Deputy District Attorney Chantal De Mauregne unsuccessfully argued for a six-year prison term in a hearing before El Cajon Judge Allan Preckel.Panem was arrested last December after another employee of the El Dorado Care Center caught him having sex with the victim. He had worked at the facility for three years.El Cajon police Officer David Vojtaskovic testified at an earlier hearing that he questioned Panem after his Dec. 26 arrest."He told me that he came in (to her room) and cleaned her up," Vojtaskovic said. "He changed her and had sexual intercourse with her."Panem also conceded that he had sex with the woman in May and November of 2009, the officer said.He said he found "practice" resignation letters written by the defendant, in which he apologized.Vojtaskovic said he tried to speak with the victim, but she kept asking him why he was there and who he was, even though he was in uniform.The woman described Panem as a friend but didn't recall seeing him that day and denied having sex with him, the officer said.