The intravenous (IV) delivery system is a common mechanism in modern healthcare, used to administer fluids, nutrients, and medications directly into a patient’s bloodstream. This setup is a complex, engineered system where the choice of material for each component is critical for patient safety and treatment effectiveness. The tubing, which is the main conduit, must be flexible, transparent, and chemically stable. The entire system is an assembly of various materials, each selected for a specific mechanical or chemical function.
Primary Materials Used for the Tubing
The material most historically and widely used for the flexible tube itself is Polyvinyl Chloride (PVC). PVC is favored primarily for its excellent flexibility, durability, and low cost, making it the default choice for high-volume, single-use medical devices. To achieve the necessary softness and pliability, PVC requires the addition of plasticizers, which are mixed into the polymer during manufacturing.
A growing number of non-PVC alternatives have emerged, driven by concerns over chemical safety and drug compatibility. Polyurethane (PU) is a key option, valued for its strength and high abrasion resistance, achieving flexibility without needing external plasticizers. Silicone is another high-performance material, frequently chosen for its superior biocompatibility and extreme temperature stability.
Other materials like Polyolefin (PO), which includes Polyethylene (PE) and Polypropylene (PP), or various Thermoplastic Elastomers (TPEs), are also increasingly used. These materials offer varying degrees of flexibility and chemical resistance, often employed to create tubing that avoids the issues associated with traditional PVC.
The Importance of Material Compatibility and Safety
The choice of tubing material is fundamentally linked to safety, primarily due to the phenomena of leaching and drug adsorption. Leaching occurs when additives within the plastic migrate out of the material and into the fluid passing through the tube. The most recognized example involves the plasticizer Di(2-ethylhexyl) phthalate (DEHP), used to soften PVC. This chemical is not chemically bound to the polymer and can escape into the infused solution.
Exposure to leached DEHP is a particular concern for vulnerable patient populations, such as premature infants, dialysis patients, and chemotherapy recipients, especially with chronic or high-dose exposure. Certain medications, particularly those that are lipid-based or highly lipophilic, can accelerate the leaching process. This has prompted a shift toward DEHP-free PVC or completely non-PVC materials in many healthcare settings.
Drug adsorption presents a different challenge, where medication molecules adhere to the inner surface of the tubing, reducing the effective dose delivered to the patient. This is especially relevant for certain hydrophobic drugs, like diazepam or nitroglycerin, which can be absorbed by plastic materials like PVC. Conversely, some non-polar drugs may adsorb less to materials like polyolefin. The interaction between the fluid and the tubing surface is a complex chemical process that directly impacts therapeutic efficacy.
Composition of Non-Tubing System Components
The complete IV system includes several hard plastic components that perform specific functions beyond simple fluid transport.
Drip Chambers
The drip chamber, positioned below the fluid source, is a transparent, usually rigid part that allows healthcare providers to visually monitor the flow rate and acts as a barrier to prevent air from entering the main line. These chambers are often made from clear, medical-grade plastics like polycarbonate or sometimes DEHP-free PVC to maintain visibility and structural integrity.
Connection Points
The connection points are standardized components designed for a secure, leak-proof interface with other medical devices. Luer lock connectors, which feature a threaded mechanism, are typically manufactured from rigid, medical-grade plastics such as polycarbonate, acrylonitrile butadiene styrene (ABS), or high-density polyethylene (HDPE). These materials are selected for their strength and ability to withstand the torque required for a secure connection.
Clamps and Valves
Other smaller components, such as roller clamps, slide clamps, and stopcocks, are also made from various polymers. Polypropylene (PP) and high-density polyethylene (HDPE) are common for clamps due to their resilience and low cost. Stopcocks, which manage fluid direction, often utilize polycarbonate for their main body and high-density polyethylene for their internal valves. Specialized inline filters, which are sometimes included to remove particulate matter, use membranes composed of materials like nylon or polysulfone housed within rigid plastic casings.