What is a sheath in medical equipment?
A sheath is a device that may be placed into a vessel at the site of percutaneous access. Sheaths permit rapid exchanges of guidewires and catheters while maintaining intravascular access. Sheaths are sized based on the diameter of the catheter or device that they allow to pass. A 7-Fr sheath accepts devices up to 7 Fr in outer diameter. A 7-Fr sheath is in fact closer to 8 or 9 Fr in diameter.