A catheter sheath, also known as a sheath, is mainly used to establish channels and guide catheters, balloon catheters, or other intravascular instruments to enter blood vessels smoothly. The sheath tube is composed of an outer sheath, an expander, and a short guidewire.
The unit of catheter and catheter sheath is F (French), F represents the circumference, and the conversion of F and mm (millimeter) is 3 F = 3 mm, so the diameter of catheter sheath of 3 F is > 1mm.
The size of the catheter always refers to the outer diameter (OD), and the catheter sheath always refers to the inner diameter (ID). Therefore, the 5F catheter can be placed in the 5F catheter sheath.
Types of Catheter Sheath
The sheath is divided into four types: ordinary sheath, check-Flo sheath, peelable sheath, and long sheath (such as the mountain climbing sheath of the opposite lower limb). The sheath tube has one side connecting interface, which can take blood samples, monitor pressure, and inject vasodilator drugs or contrast agents during operation. At present, SCW Medicath Ltd. sells five generations of different catheter sheaths in the market, including Medtronic, Johnson & Johnson, and Terumo, most of which are sold abroad. The size of the catheter ranges from 4f to 9F and the length is 9-23cm respectively. 4f and 5F can be used for a radial artery with a smaller diameter, also known as trans-radial artery sheath. For ease of use, these catheter sheaths are sold in sets. According to the size, the suit is equipped with a puncture needle, guidewire, expansion tube, syringe, and blade of the corresponding size.
Steps to Use Catheter Sheath
After determining the arterial puncture point, first, select a suitable sheath, soak the sheath and its supporting expander with heparin saline, and flush its lumen. At the beginning of the operation, turn off the switch of the sheath sidearm. The expander base needs to be locked to prevent it from exiting when the sheath enters. After the sheath enters, the supporting guidewire can be inserted to ensure the entry of the sheath and serve as a track for other instruments.