A padded cell is a special room in a hospital for mentally ill people. It's made so that the patients can be put there when they go through a crisis (or they have a fit or seizure). They are put there so they can go through their crisis on their own, without putting others into danger. Padded cells are made in special ways so that those having the crisis cannot hurt themselves. Padded cells have been used for a long time in psychiatry. In the 1980s, their use declined in Europe. This is because there are drugs that can be given that make them nearly unnecessary.
Seizures and crises are usually very tiring. For this reason, patients usually only spend a short time in these cells. They usually collapse because of fatigue rather quickly. When they do, they need medical attention quickly.