New IV Set Replaces Silicone

Fluid administration through a pump system controls the infusion rates of the solutions.

Frequently the patients require that the solutions or drugs administration is made in very precise quantities or specific infusion rates.  For this type of applications the industry has implemented the infusion system through the utilization of administration pumps, which control electronically or mechanically the infusion rates of the solutions.

The conventional design of the infusion equipments for these pumps; counts on a silicone segment, which is a flexible material whose properties of compression allow the IV set its adaptation to the pump. In order to obtain the required flow rate there are different types of functional mechanisms of the pump; a common system consists on pressing the tube segment in a peristaltic movement.

A cost-effective alternative for the silicone segment is given through an evaluation of new PVC compound DEHP free. This is a Class VI material according to the UPS requirements for medical applications. The physical properties, as well as mechanical and cosmetics of this PVC formulation accomplish the equivalent aspects and functionality as an excellent option for replacing silicone. Additionally this PVC formulation is unique in this texture and confers an appearance similar to silicone.

This new concept in flexible PVC compounds offers unique characteristics that let this application be an excellent replacement for thermoplastic rubbers, at the same time it allows an exceptional stability and simplifies the manufacturing process by permitting conventional extrusion. It’s ideal for equipments that require weatherability and, to improve their physical properties.

This type of material is ideal for medical applications where economies of scale are a key factor nowadays. The material has shown excellent properties as a replacement for silicone in applications where high performance is required, without pressing deformation, such as the deformation that tubes present on peristaltic pumps 

Important features of the Flexible PVC vs. Silicone for medial equipments:

• Cost-effectiveness.
• It can be assembled to other plastic components with conventional solvent.
• It simplifies the sterilization process including gamma.
• Appropriate hardness of material for manipulation and elimination of collapsed parts once it’s placed on the infusion pump.
• It can be processed in conventional extrusion equipments.
• Equivalent compression properties and resistance.

This Flexible PVC was applied during the development of a replacement for the silicone tubing segment. This segment is the essential component in an infusion set for fluid administration for pump application, which allows the control of the required infusion rate.

To obtain the tubing with the Flexible PVC an extrusion characterization was conducted with different tests to find the extrusion conditions and optimum parameters for the process of this new resin (temperature at different zones of the barrel, cooling water, rpm’s, etc.) in order to provide high quality pieces according to customers’ required attributes, design and specifications.

During the evaluation of the components’ assembly process for the IV set, several tests were applied to determinate the appropriate solvent for bonding the Flexible PVC tube with the other plastic parts, which results of assembly resistance (pull test), integrity, finished and stability allow the selection of the better solvent for the assembly process.

On the design evaluation stage, the functionally of the New IV set was verified with a protocol for a pump, making a comparison versus an IV set with silicone segment. On the DOE (design of experiments) different infusion rate conditions and time of infusion were evaluated, taking as reference the IV set with the silicone segment to verify the performance in the pump. The principal result considered was the difference between the programmed flow rate and the real delivered fluid. A common use solution was utilized in this test. Additionally in the experimentation the lost liquid by evaporation was considered as well as the temperature and relative humidity to check the environmental conditions of the tests.

The tests that were applied for each material are shown on Charter 1. 6 Subgroups were indicated with 5 samples each. For each Subgroup different infusion rates and conditions were considered. The solution used for the testing was a saline solution (9gr NaCl/ 1000ml). 

Charter 1. Experimental conditions for each material.

Where:

Q_t= Theoretical Infusion rate programmed on the Pump.

t_t= Test total Time.

V_tt= Theoretical total Volume.

Δt_i= Time Intervals considered in each test (Δt_i=t_i-t_i-1)

t₀= Initial time.

V_ti= Theoretical time for each time interval.

n= Number of time intervals considered for each test.

According to this, we can apply:

Q_ti= Theoretical infusion rate in each time interval.

The environmental conditions for the study are considered between 19.6°C - 22.8°C. The relative humidity is considered between 45 - 59 percent.

Figure 1 shows the observed results on the Infusion pump specifically for each subgroup, using silicone tubing and the alternative compound. A variation of +/-5 percent can be observed. 

Figure 1. % Error vs. Subgroups evaluating Silicone vs. PVC.

On the other side, Figure 2, presents the tipical behavior of both materials in the time. 

Figure 2. Tipical behavior found with silicone and PVC (observed on subgroup 5 for a specific pump).

The pump used for the evaluation included special features:

• Obstruction sensor. To detect the obstruction of the flow.
• Integrated clamp. To prevent the free flow when the door of the pump was opened.
• Bubble sensor. To detect air presence in the tube.

With the design validation, was verified that, the new Pump IV set that replaces the Silicone for a Flexible PVC compound, meets the functionality equivalence for the application, since a significant difference in the behavior between these two materials (silicone and flexible PVC), through time and different flow conditions did not appear.

In this product a substitute for silicone was found by using a Flexible PVC DEHP Free, which provides the same quality frame with a significant cost-effectiveness.

For more information visit www.pympsa.com