Washington DC - The woman who survived a botched execution attempt was still hospitalized in critical condition and on a ventilator, her lawyer said Sunday as he called for her death sentence to be commuted to life in prison.

Tennessee's prison chief resigned Saturday after convicted murderer Christa Pike (50) survived two lethal injections of pentobarbital, a drug that suppresses nervous system activity.

The case gained national attention and raised questions about capital punishment in the US and the methods used to carry it out.

"She's still in the hospital on a ventilator, critically ill," Pike's attorney Stephen Ferrell said on CNN. "We don't really know the prognosis yet, and may not know for several days."

Ferrell, who has been unable to see his client, said doctors were still trying to rid her body of the drug while she remains under guard at the hospital.

He urged Governor Bill Lee to show leniency.

"I think, at the very least, the governor should commute Ms. Pike's death sentence to a life sentence," Ferrell said. "We don't know what her physical state will be, but it is clear that she has endured a torturous attempt at executing her."

He added: "I think she's spent over 30 years in prison, most of that in solitary confinement, only to be taken out and not executed, but tried to execute her. And that we don't know right now, and we may never know what sort of torture she endured during that process."

Media witnesses listened to Pike snoring for about an hour after she was given the injections, and said she was alive as they were ushered out of the execution chamber viewing area at the Riverbend Maximum Security Institution in Nashville.

In his resignation statement, Tennessee Department of Correction Commissioner Frank Strada insisted "the Department carried out its responsibilities in accordance with the established protocol."

Lee, who previously denied Pike clemency, has halted further executions through the rest of the year pending a third-party review.

Pike's case sparked debate over the death penalty for young offenders, as she was 18 when she and her boyfriend beat and killed 19-year-old Colleen Slemmer at a job training camp in 1995.

Pike's lawyers sought clemency, citing her age, childhood sexual abuse, and mental health problems, including post-traumatic stress disorder.