The basic idea is that the Medium goes into a deep meditation before the Trance Healing begins.

Thus, the Medium must reach a state of trance. This helps them to connect to the spirits that bring the healing energy. In this process, the energy fields of the Medium and the Spirit Friends will blend.

Hence, if the Medium is doing a healing session for someone else the healing energy is transferred from spirit, through the aura of the medium, to the client.