Model B Interchangeable mattress is made up of the air mattress and the air pump; the air supply system in the pump can drive the two air channels ten times per hour regularly. The air mattress is made up of two separated tube-like air rooms, which are connected with the two air channels of the pump and waves alternatively with them to change the part of pressure of the patient. It can effectively prevent from and cure bedsore; the slight roll is just like massage to increase the blood circulation of the patient.