# Medical Catheter Packaging Tube (Protective Sheath / Support Tube) Basics

A packaging tube, also known as a **protective sheath, liner tube, or support tube**, is placed inside the sterile inner packaging and surrounds the catheter to prevent crushing, kinking, or twisting. It is commonly used for interventional catheters, long catheters, and thin-walled soft catheters. The tube does not directly participate in sterilization or serve as a breathable barrier; instead, it functions as an internal protective component. China Food and Drug Administration... 。

I. Common Materials for Protective Tubes

1. **PP (Polypropylene)**: Most commonly used, with moderate hardness and medical-grade quality. Excellent resistance to EO (ethylene oxide) and radiation sterilization, low cost; transparent or semi-transparent, allowing internal catheter visibility.

2. **PE (Polyethylene)**: Softer in texture, suitable for slightly curved catheters, good crack resistance but insufficient rigidity, weak support for long catheters.

3. **PET (Polyethylene Terephthalate)**: High rigidity, thin wall, excellent dimensional accuracy; note that some PET materials are not resistant to repeated bending.

> Must be **medical-grade material**, with biocompatibility and leachables testing performed; ordinary industrial plastic tubes must not come into direct contact with catheters.

II. Structural Types

1. **Straight Tube (Through-the-Tube Sleeve)**  

The entire catheter is inserted through the tube, both ends open, suitable for long straight catheters; often combined with blister packs and protective sleeves.

2. **Split C-Shaped Sleeve (Grooved Tube)**  

Longitudinal slot on the side allows easy insertion of the catheter without threading from one end, improving assembly efficiency; drawback: slot edges must be smooth to avoid damaging the catheter outer wall.

3. **Spiral Wrap (Helical Sheath)**  

Flexible design allows moderate coiling of the catheter, preventing kinking; ideal for catheters requiring coiled packaging.

4. **Short Protective Cap (End Caps)**  

Only covers the tip and connector sections of the catheter, protecting the tip, coating, and radiopaque marker; main body remains uncovered, with positioning via blister tray slots.

III. Key Design Considerations

1. **Internal Diameter Clearance**  

The inner diameter of the sleeve must exceed the outer diameter of the catheter, leaving a reasonable gap—never tightly constricting the catheter. After heat sterilization, it must not compress the catheter and cause permanent deformation. Excessive tightness may flatten the catheter during EO sterilization due to heat.

2. **Tube End Edges**  

Tube ends must be chamfered and deburred; sharp cuts can scratch the catheter surface, causing cracks or coating delamination.

3. **Length**  

The protective tube length should fully cover the section requiring protection. The tip must not extend beyond the catheter tip to prevent puncturing paper-plastic or Tyvek sterile bags, leading to package leakage.

4. **Sterilization Compatibility**

- **EO Sterilization**: PP, PE, and PET are all compatible; the sleeve must not completely block the catheter lumen to ensure gas circulation.

- **Radiation Sterilization**: Prefer modified PP with radiation resistance; some standard PP may become brittle and crack after irradiation.

5. **No Debris Release**  

The sleeve must not shed particles or powder; cutting should be performed in cleanroom conditions to prevent debris contamination within the packaging.

IV. Assembly and Packaging Integration

1. Protective sleeves are **inner packaging components**, sealed together with the catheter inside paper-plastic bags, Tyvek bags, or rigid blisters, and sterilized as a unit.

2. The sleeve cannot serve as a sterile barrier; the primary sterile barrier remains the combination of dialysis paper/Tyvek and heat-sealed film; the sleeve provides only physical protection.

3. For coiled packaging: the sleeve must not force bends smaller than the catheter’s minimum bend radius, otherwise internal kinks will form, rendering the product unusable.

4. Blister solution: Catheter positioned by blister tray grooves, with protective sleeve providing secondary protection—ideal for high-value interventional catheters.

V. Common Defects

1. Sharp burrs on the sleeve scratch the catheter outer wall;  

2. Insufficient inner diameter causes compression during EO sterilization, flattening the lumen;  

3. Sharp sleeve ends pierce the sterile bag, compromising sterility;  

4. Grooved C-sleeve openings pinch the catheter;  

5. Radiation-induced brittleness leads to sleeve fragmentation and particle release;  

6. Excessively long sleeves puncture the bag film.

VI. User Instructions

When clinicians open the packaging and remove the catheter, discard the protective sleeve immediately. The protective sleeve is not a component intended for use in the human body and must never be inserted into a patient.

VII. Simple Differentiation

- Sterile barrier: Paper-plastic bag, Tyvek, blister cover film (responsible for sterility and breathable sterilization)  

- Packaging protective tube: PP/PE/PET sleeve (only protects against pressure and bending; does not ensure sterility)