Cryogenisis suspension was a freezing procedure that was in use during the Clone Wars era. The procedure involved injecting a willing participant with the coma-inducing drug Dx31-B and then putting the subject into a cryogenisis suspension chamber. Once inside the chamber, life support was activated and the suspension timer was activated, if so chosen by the doctor in charge. After the set time was up, the participant would awaken and would be allowed back out. However, it seems, by the end of the Sith Crusade, this product had been outlawed, as there were no more shipments of Dx31-B being sent to the government. It is unknown when or why that this procedure was outlawed, but one can guess that it was due to the dangerous nature of the procedure, as in 1/3 of the patients injected with the drug, they all developed side effects and some of them even died.
The only known participant of this experiment was the Sith Admiral Negee Hoessatch, and he wasn't even a willing participant. He was kidnapped in 20 BBY and put inside one of the machines. He was freed almost 80 years later, by Admiral Strasbourg. It is unknown if Strasbourg's descendant was the one who kidnapped Hoessatch, or if it was totally unrelated.