A CIA inspector general's report issued in 2004 was more critical of the agency's use of sleep deprivation than it was of any other method besides waterboarding, according to officials familiar with the document, because of how the technique was applied.
The prisoners had their feet shackled to the floor and their hands cuffed close to their chins, according to the Justice Department memos.
Detainees were clad only in diapers and not allowed to feed themselves. A prisoner who started to drift off to sleep would tilt over and be caught by his chains.
The memos said that more than 25 of the CIA's prisoners were subjected to sleep deprivation. At one point, the agency was allowed to keep prisoners awake for as long as 11 days; the limit was later reduced to just over a week.
According to the memos, medical personnel were to make sure prisoners weren't injured. But a 2007 Red Cross report on the CIA program said that detainees' wrists and ankles bore scars from their shackles.
When detainees could no longer stand, they could be laid on the prison floor with their limbs "anchored to a far point on the floor in such a manner that the arms cannot be bent or used for balance or comfort," a May 10, 2005, memo said.
"The position is sufficiently uncomfortable to detainees to deprive them of unbroken sleep, while allowing their lower limbs to recover from the effects of standing," it said.
In the Red Cross report, prisoners said they were also subjected to loud music and repetitive noise.
"I was kept sitting on a chair, shackled by hands and feet for two to three weeks," said suspected Al Qaeda operative Abu Zubaydah, the first prisoner captured by the CIA, according to the Red Cross report. "If I started to fall asleep, a guard would come and spray water in my face."