COLUMBUS, Ohio — An Ohio inmate facing execution next week from an untried method is at substantial risk of a medical phenomenon known as air hunger, which will cause him to experience terror as he strains to catch his breath, an anesthesiologist testified Friday at a federal court hearing.

Because condemned killer Dennis McGuire has several characteristics of someone with sleep apnea, or the struggle to breathe while asleep, the chances are even greater he will be subjected to feelings of suffocation, said David Waisel, a professor at Harvard Medical School.

“Mr. McGuire is at a substantial risk of experiencing the terror of air hunger during the first five minutes of the execution,” Waisel testified as a witness for defense attorneys trying to stop McGuire’s execution Thursday.

“Air hunger is a horrible feeling,” Waisel added. “It’s the inability to get your breath.”

Waisel testified at the beginning of a two-day hearing on the state’s new lethal drug process.

Ohio plans to use intravenous doses of two drugs, midazolam, a sedative, and hydromorphone, a painkiller, to put McGuire to death. The method has been part of Ohio’s execution process since 2009, though never used. It was chosen because of a shortage of other lethal injection drugs.

The Constitution bans executions that constitute cruel and unusual punishment. But that doesn’t mean procedures that are entirely comfortable, an assistant Ohio attorney general told Frost.

“You’re not entitled to a pain-free execution,” attorney Thomas Madden said.

Such dueling arguments have taken place often in federal Judge Gregory Frost’s courtroom over the years. Frost has heard numerous arguments for and against Ohio’s lethal injection process.

He has never ruled the drugs themselves unconstitutional, but he has at times harshly criticized the state for conducting haphazard executions.

McGuire, 53, was sentenced to die for the 1989 rape and fatal stabbing of Joy Stewart in Preble County in western Ohio. The 22-year-old Stewart was newly married and pregnant.

“McGuire will experience the agony and terror of air hunger as he struggles to breathe for five minutes after defendants intravenously inject him with the execution drugs,” the inmate’s attorneys said in a Monday filing.