A surgical instrument that includes a distal member configured to receive a pneumatically operated tool assembly therein. The instrument may also include pneumatically powered drive member configured to generate at least one actuation motion upon receipt of at least one pneumatic signal from a source of pneumatic power fluidically coupled thereto. A drive shaft assembly communicates with the pneumatically powered drive member for transmitting the actuation motions to the distally mounted pneumatically operated tool. The device further includes a power assist member that communicates with the drive shaft assembly for transmitting additional manually generated actuation motions to the drive shaft assembly.