Stasis

Stasis, also known as suspension, is a state of suspended animation in which a person subject to the process is chronologically frozen. The subject is unconscious, and cannot move, think, or speak.

Side Effects
Stasis has some known side effects. Being in stasis for a period of a couple months may cause cognitive deterioration, while staying subject to it for a couple years may cause serious brain damage. The effects of being under stasis for a short period of time are unknown.

Portal
At the beginning of Portal the player character,Chell, wakes up from stasis in the Relaxation Vault. The amount of time she had been in suspension was undefined. This is the only appearance of stasis in Portal.

Portal 2: Lab Rat
In the Portal comic Lab Rat, which is set between Portal and Portal 2, shows stasis on two occasions.

Portal 2
In Portal 2 the player character wakes up from Stasis after 50 days and is asked by the Announcer to do a mandatory physical and mental wellness exercise. The player goes into stasis again. The player then reawakens after an extremely long time, too long for the announcer to compute. This is the only appearance of stasis in Portal 2.

Appearance
The bed in the relaxation vault is evidently some kind of medical equipment. At the front there is a screen and near the back there are canisters of a undefined substance. This is very different to the bed found in The Extended Relaxation Centre which is made to look like a normal bed and does not show any signs of how it works.