The revision concerns the rules on the record keeping of information about inmates and the management of their files, the treatment of women prisoners, foreign nationals, as well as the use of special high security or safety measures such as the separation of prisoners from other inmates, solitary confinement, instruments of restraint, the need to ensure adequate levels in prison staff, inspection and independent monitoring.
The recommendation regulates in greater detail solitary confinement (i.e. being locked up for more than 22 hours a day without meaningful human contact). Decisions on this measure should always be used as a last resort and take into account the state of health of the prisoner. Due to the very negative effect such a measure may have on one’s physical and mental health, it should be imposed for a strictly specified period of time, which should be as short as possible.
The revised rules establish that states should set in their national legislation the maximum period for which solitary confinement may be imposed. Furthermore, inmates concerned should be visited daily by the prison director or an authorised member of the prison staff, as well as by the medical practitioner.

You can download the complete document of the Prison rules here.