A medical instrument , comprising: an elongated outer housing with a hollow inner plenum , wherein a distal end of the elongated outer housing includes an outer shaft distal opening ; a main body extending proximally from a proximal end of the elongated outer housing ; an inner drive shaft positioned within the elongated outer housing and extending into a hollow cavity within the main body , wherein the inner drive shaft is sized such that a flushing fluid plenum exists in the hollow inner plenum of the elongated outer housing between an outer surface of the inner drive shaft and an inner surface of the elongated outer housing ; a drive system in communication with the inner drive shaft and extending radially outward from the main body , wherein the drive system is configured to move the inner drive shaft axially within the hollow inner plenum of the elongated outer housing ; and an instrument flushing system in communication with the hollow cavity within the main body and configured to pass flushing fluid through the hollow cavity within the main body and through the flushing fluid plenum in the hollow inner plenum of the elongated outer housing between the outer surface of the inner drive shaft and the inner surface of the elongated outer housing ; characterized in that the instrument flushing system further comprises at least one standoff positioned in the flushing fluid plenum and extending between the outer surface of the inner drive shaft and the inner surface of the elongated outer housing to maintain the flushing fluid plenum ; wherein the at least one standoff of the instrument flushing system is formed from a collar extending radially outward from the outer surface of the inner drive shaft , wherein the collar includes at least one axially extending groove therein positioned on a radially outer surface of the collar . an elongated outer housing with a hollow inner plenum , wherein a distal end of the elongated outer housing includes an outer shaft distal opening ; a main body extending proximally from a proximal end of the elongated outer housing ; an inner drive shaft positioned within the elongated outer housing and extending into a hollow cavity within the main body , wherein the inner drive shaft is sized such that a flushing fluid plenum exists in the hollow inner plenum of the elongated outer housing between an outer surface of the inner drive shaft and an inner surface of the elongated outer housing ; a drive system in communication with the inner drive shaft and extending radially outward from the main body , wherein the drive system is configured to move the inner drive shaft axially within the hollow inner plenum of the elongated outer housing ; and an instrument flushing system in communication with the hollow cavity within the main body and configured to pass flushing fluid through the hollow cavity within the main body and through the flushing fluid plenum in the hollow inner plenum of the elongated outer housing between the outer surface of the inner drive shaft and the inner surface of the elongated outer housing ; characterized in that the instrument flushing system further comprises at least one standoff positioned in the flushing fluid plenum and extending between the outer surface of the inner drive shaft and the inner surface of the elongated outer housing to maintain the flushing fluid plenum ; wherein the at least one standoff of the instrument flushing system is formed from a collar extending radially outward from the outer surface of the inner drive shaft , wherein the collar includes at least one axially extending groove therein positioned on a radially outer surface of the collar . <EOS>