A patient support system for a wheelchair is provided. At least a portion of the patient support system components form a no-air-loss patient support surface. At least one fluid pump can supply air pressure to a plurality of no-air-loss air cells, and at least one pressure release valve can release air pressure from the no-air-loss air cells. A computer can compare air pressure within the air cells to a desired air pressure set point and can modulate the air pressure by actuating the at least one fluid pump and/or the at least one pressure release valve to bring the air pressure within the air cells to a desired air pressure. After the initial air pressure adjustments are made and the desired air pressure is achieved, no further adjustments during the operation are able to be made by the computer so that the patient positioned thereon the patient support system will not be moved by the patient support system during an operation.
