Unique medical needs of animals

Editor's Note: We have not gone to the dogs...and we are not changing the focus of TMD from humans to animals... but we found this article of great interest from a number of angles. First is the growing market for advanced medical treatment of animals, from livestock to your favorite furry friend. Next, the basics and concepts are the same – the need for high quality, dependable medical devices and components continues to grow. As the need increases, there can be synergy of ideas from one marketplace to the next. Finally, yes, the FDA is involved in the veterinarian market with the FDA Center for Veterinary Medicine division. We hope you enjoy this as much as we did.
 

Fluid delivery through IV devices for medicating animals can be a difficult procedure for veterinarians. However, the Flex-Coil Swivel System IV device – a registered trademark of International WIN Ltd. – makes the process easy, safe for the animal, and less labor intensive for the veterinarian.

Key to the success of the Flex-Coil Swivel System is a unique seal designed by Minnesota Rubber and Plastics (MR&P). It provides bi-directional sealing to contain and control fluid passing through a center pin that turns freely within the seal. The assembly provides 360° swiveling motion of the hollow center pin, allowing free movement of the animal during treatment.

Until design of the Flex-Coil Swivel System IV device, administering fluids such as nutrients, blood, antibiotics, and other medications to dogs, cats, and larger animals – such as foals and calves – depended on unreliable and improvised devices. The most common problem was that with normal movement, the animal disconnected the IV, became entangled, and/or chewed the tubing. Administration of continuous IV fluid, especially through the night, required continuous monitoring and repeated attention to the IV attachments to keep it working properly.


The System
The device consists of a series of tubes, coils, and connections that center and function from a mounted housing located above the caged animal patient. This housing snaps into and out of a shoe affixed to the top of the cage or holding area, and contains the seal assembly that is the key to the overall function and success of the Flex-Coil Swivel System IV device.

Shown here are the individual components that make up the seal assembly in the Flex-Coil Swivel System IV device.Inside the housing, the seal and related assembly connects to coiled tubing that connects to an IV catheter inserted in a vein and attached to the animal’s body. The coiled tube flexes easily when the animal moves and shifts position. Expanding and contracting, the coiled tubing allows free movement without the animal’s legs or body entangled in it. Most important, the swivel device allows full 360° rotation without twisting, binding, or disconnecting the tubing. Fluid delivery continues uninterrupted at the prescribed rate.

The fluid bag or container (that contains blood, nutrients, antibiotics, saline, etc.) attaches to the tubing (above and outside or high in the cage or enclosure) and leads to the mounted housing. This keeps the fluid supply, infusion pump (when used), and the drip mechanism out of harms’ way and away from any movement that the animal might make.

What is so clever about this device setup is that even if the animal becomes highly agitated and does a lot of jumping and twisting, the Flex-Coil Swivel System IV device keeps the animal clear of the coiled tube and IV connections. With this setup, the animal cannot see the IV attachment, bite at it or the coiled tube, and therefore leaves it alone.


Addressing Seal Problems
“Coming up with the right seal was a real challenge when the technology for delivering IV fluids advanced about five years ago,” reports William Donawick, DVM, president of International WIN Ltd., and inventor of the Flex-Coil Swivel System IV device. “Our original design had a one-way seal with minimal friction. It worked well for the time but as more veterinarians included infusion pumps and longer tubing in their IV setups, the potential for problems arose. Use of infusion pumps occasionally created a negative pressure in the IV tubing causing dangerous air bubbles to enter.

“In addition, when longer IV tube setups were used, gravity and distance allowed small amounts of air to get into the IV. We had to find a seal to solve both of these leak conditions and one that also provided free 360° swiveling motion. It was that or discontinue the product.”

MR&P supplied the seals in the original Flex-Coil Swivel System IV device. Donawick says that he knew of the company’s long history in designing special application seals for unusual applications.

“So we challenged them to see what they might recommend to replace the original seal,” Donawick explains. “It was a monumental task because nothing quite like this had been done before. But, Chris Mauhar, design engineer for MR&P, saw this opportunity to do something really different. He and his team came up with the solution. The success of the Flex-Coil Swivel System IV device really depended on the function and reliability of that new seal design.”

“Dr. Donawick was an ideal customer to work with because he had a good sense of design and helped [us] to overcome the design challenges,” Mauhar states. “Together we recognized that conventional seals would not handle the opposing pressures in the IV line, while at the same time providing the needed 360° swiveling feature. Dr. Donawick envisioned a seal that worked with the squeegee effect of a windshield wiper blades alternating motion. Playing off that concept, we came up with a double lip seal design so that the lip facing up would contain the downward fluid (positive) pressure. The lip facing down would handle the upward fluid (negative) pressure.”

This was only half of the solution, however. The rotating hollow center pin (to allow fluids to pass through it) held in place by the seal, housing, and cap of the assembly, had to swivel freely in a 360° motion without leaking when an animal patient pulled, twisted, and turned the IV set. To function properly and deliver IV fluids at the correct rate without leakage, the seal required the right material formulation, exact sizing, and molding to consistently tight tolerances.

Using Solid Works 3D modeling software, Mauhar and his MR&P team created a seal design concept with double lips that had extreme side-loading resistance. Donawick, in turn, designed a protocol for testing these CAD designed parts, allowing MR&P to verify its theoretical seal designs.

Mauhar used finite element analysis (FEA) throughout the development stages. FEA was first used for the original double lip seal design and then to revise the design when testing showed problems.


Material selection critical
Drawing on its more than 50 years experience developing custom elastomers for difficult medical applications, the MR&P team settled on a specially formulated Ethylene Propylene Diene Monomer (EPDM) compound. Formulated and molded to ensure low extractables, the seal material was compatible with the wide range of fluids available for administration through the IV system.

Size of the seal also was important. Through various size iterations and testing, final dimensions were: 0.346" OD, 0.140" ID and 0.145" thickness.

Maintaining tolerances also was critical to product success. MR&P’s ensured repeatable quality, with its state-of-the art molding operations, results in tolerances on the following critical dimensional surfaces: ID ±0.004", OD sealing diameter dimension (0.295") held to ±0.005"; and sealing thickness (0.195") held to ±0.005".

Keeping the seal design as small as possible was a cost saving and had functional benefits as well. The small seal allowed just the right capacity for correct fluid flow with no leakage. This small seal design also created less friction than a comparable larger design. (Excessive friction caused the coiled tubing to kink when the animal moved). MR&P designers improved the low friction feature by applying a medical grade silicone lubricant to the seal prior to assembly.


Precision Components
The complete seal and bearing assembly is a combined effort of MR&P and Wycon Mold & Tool Inc.

The Flex-Coil Swivel System IV device consists of the following components: (1) injection molded polycarbonate mounted housing with fluid chamber that holds the seal and bearing assembly; (2) injection molded thermoplastic rotating hollow center pin that rotates in the seal; (3) transfer molded EPDM formulated double lip seal; (4) stainless steel washer; and (5) injection molded thermoplastic cap.

To assemble, the seal and washer slide onto a hollow center pin inserted into the housing sleeve. The cap, when bonded to the housing, creates a fluid reservoir chamber, holds the top of the center pin in alignment, and prevents formation of side forces that could deform the seal and allow leaks. The cap locks the entire seal assembly into place. The freely rotating pin is then ready to connect to the coiled IV tubing.

Final steps include testing to be certain the center pin turns freely; testing the swivel assembly for leaks with positive air pressure and a vacuum; and spinning the pin for 30 seconds to evenly distribute the medical silicon lubricant. Needed medical tubing and connectors are attached to the coil and the completed sets are packaged and sterilized with Ethylene Oxide (EtO).

All design work for the Flex-Coil Seal System IV device, and a 73-cavity production mold, were done at MR&P headquarters. Molding was performed at the company’s Watertown, SD.

“The Flex-Coil Swivel System IV device, with the new sealing assembly, has been used successfully by veterinarians all over the world for nearly two years,” Donawick reports. “We really owe its success to the seal device Chris Mauhar and the MR&P team designed and continue to manufacture for us.”

Watch the video at OnlineTMD.com/flex-coil-iv-system.aspx for a close up look at the system.


Minnesota Rubber and Plastics
Minneapolis, MN
mnrubber.com

International WIN Ltd.
Kennet Square, PA
internationalwin.com

Wycon Mold & Tool Inc.
Warminster, PA
wyconmold.com