A surgical apparatus includes a shaft having a proximal end and a distal end, an end effector coupled to the distal end of the shaft, and a sheath disposed on an external surface of the instrument shaft. The sheath includes a material that is permeable to gas so as to permit equalization of a pressure differential after insertion of the sheath and shaft into an environment at a surgical insufflation gas pressure. The pressure differential is between an insufflation gas pressure and an initial pressure lower than the insufflation gas pressure.