Patent ID: 7918831

Claim:
A catheter assembly comprising: a catheter; and a sheath, made of a liquid-impermeable material that is sterile or able to withstand sterility treatment, impermeable to bacteria and other contaminants, and gas-permeable, surrounding and enclosing at least an insertable portion of the catheter, the sheath composed of a microporous polyolefin material, the microporous polyolefin material made by taking a microporous polyolefin matrix and filling pores of the microporous polyolefin matrix with a moisture-vapor permeable, liquid-impermeable, hydrophilic material to prevent the passage of liquids through the microporous polyolefin material while readily permitting passage of moisture vapor, the sheath preventing air buildup at a distal end of the sheath as the sheath bunches up during insertion of the catheter, the sheath preventing the air buildup by transferring air through a wall of the sheath to an outside atmosphere, wherein a gap in the sheath at the proximal end created during insertion is not of such size to allow venting into the sheath.