Tubing Comes Into Its Own
As an Integral Component of Minimally Invasive Surgery, Quality Medical Tubing Is in Great Demand
Frank Celia, Contributing Writer
Minimally invasive surgery is that rarest phenomenon in the medical world: something everybody loves. Surgeons love it because it lowers postoperative complications and liability. Insurance companies love it because lowers costs. Patients love it because it reduces pain and shortens hospital stays. And governments love it for all those reasons combined. It’s not every day that these four groups get on the same page about anything.
As advances in medical-grade tubing continue to permeate the market, a wide array of options are available today. Photo courtesy of MicroLumen.
But the smaller-is-better trend has other effects as well, and one of them is greater demand for medical grade tubing. Yesterday’s surgery scalpel is being replaced by today’s articulating cannula, catheter, electrical coil, laparoscope and endoscope—all of which involve some kind of tubing. Tubes also are increasingly used to deliver medical devices into the body; stents, which are becoming more popular than ever, are one example of these devices. Finally, implantable tubes are needed to insulate the electrical wires for which product designers are finding more use, such as wires employed in pacemakers and neurostimulation.
All this has made for explosive growth among tubing manufacturers, which historically tend to be small, mom-and-pop operations that cater to a limited, regional clientele. This situation is beginning to change, as more money and demand flow into the field. Consolidation has begun, and companies are being pressured to provide additional services, such as process validation, that previously were not seen as a major priority.
Following is a look at how these forces and others are shaping this burgeoning industry.
Extrusion Process: A Mainstay in Tubing
Most industrial quality tubing is manufactured by a technique called extrusion. There are other ways to manufacture tubing, such as injection molding, but to create long lengths of product, extrusion is the most financially viable option and is the one most often used.
Extrusion techniques vary widely, and some companies have developed proprietary extrusion designs. But in general one of the first steps is to dry the polymer material that will be used to manufacture the tube. Many polymers used in the medical industry absorb moisture from the air, and so they must be dried before being employed in the extrusion process.
Next, the material usually is melted in the extruder and pushed through a die at a steady rate, usually by an auger-like screw. The die, located at the opposite end of the extruder, forms the shape of the tube when the molten material is forced through it. The part of the die that forms the inner diameter of the tube is called the mandrel, and the part that forms the outer diameter is called the ring. Extruder dies have many complex designs, and there are dozens of companies that specialize in manufacturing them. The die is important because it is the component of the process that determines the precision and quality of the tube’s physical properties.
Responding to market demands for smaller diameters and more resilient materials, tubing companies employ the latest technology to improve and expand the services they’re able to offer OEM customers. Photo courtesy of ExtruMed.
Usually located after the cooling system on an extruder line, a pulling apparatus drags the tubing out of the die. The final step typically is a machine cuts the tubing or rolls it into a spool. Secondary operations may placed anywhere along the extruder line.
As far as production lines go, extrusion tubing is the not the most complex in existence. The challenge for a contract manufacturer is to customize each tubing request and to do so quickly and accurately. “If you are running the same part day-in and day-out, you can make extrusion into a science,” said Apur V. Lathiya, chief operating officer of ExtruMed, one of the industry’s largest custom tubing manufacturers, based in Placentia, CA. “But when you are constantly extruding different tubing configurations using different materials and possibly different equipment, you have to know the nuances of this process. There is a lot of what people call ‘black art’ to it. Experience with different resins, designing the tooling to get the plastic to flow just the way you want and manipulation of the processing parameters to hold tight tolerance, both dimensionally and cosmetically—these are just some of skills that separates extrusion companies from each other.”
Often the final tubing product will require secondary operations in order to maintain the high quality and tight tolerance necessary for medical applications. One common secondary step is called annealing. During the extrusion process the material of the tube is pulled and stretched to a high degree. Thus, when the finished tubing product sits on a shelf for a few weeks, it begins to shrink back to its natural dimensions. It is in the manufacturer’s interest to hasten this process, making sure the tube reaches its natural dimensions before being shipped to the buyer. Annealing is the process by which tubing is placed for a period of time in a hot air oven, which rapidly shrinks it back to the material’s relaxed size.
Heat-Shrink Tubing Aids Smaller Devices
Like all areas of medical device manufacturing, extrusion houses are being asked to produce smaller parts that still retain the function and efficacy of their bigger predecessors. (A joke among tubing shops: the client asks for a tube whose inner diameter is larger than its outer.) To meet this demand for smaller tubes with thinner walls, many companies are turning to heat-shrink tubing. This manufacturing process can be used to create catheters of variable stiffness, tubes for electrical insulation, to join and transition tube products, to create catheter tips, as well as many other applications. Heat-shrink tubing is a rapidly growing part of ExtruMed’s business, Lathiya said, representing a significant percentage of the company’s current sales.
“Most of the heat-shrink tubing we manufacturing is used as a manufacturing tool in catheter and tubing assembly. Whether our customer is manufacturing a variable stiffness shaft or reflowing a polymer over a braid, the heat-shrink is a useful tool in enabling the assemblers to accomplish their task,” adding that very few companies can achieve the extreme wall thinness that ExtruMed can obtain with its heat shrinking process. Furthermore, the company is continuing to push the technology with different materials and higher performance levels.
New clinical therapies are increasing challenges and opportunities for today’s tubing suppliers. Manufacturers are responding with a mixture of tried-and-true techniques and cutting-edge 21st century materials and technology not available just a few years ago. Photo courtesy of ExtruMed.
The manufacturing of heat shrink is a three-step process that includes extrusion, irradiation and expansion. ExtruMed designs and manufactures the extruded tubing, then outsources the cross-linking step of the process. Finally, the expansion step is performed in-house using the company’s custom-designed equipment, according to Lathiya. Common materials employed in this process are polyethylenes of varying densities, ranging from low-, medium-, and liner-low density.
Another growing area of ExtruMed’s business is manufacturing implantable grade tubing. Designing devices to be used in a medical setting already is fairly difficult, but an additional level of complexity is added to applications designed to stay in the body for decades, Lathiya noted. (See “Neurostimulation Growing Market for Tube Makers” on page 46.) But his company does not shy away from this challenge.
“In implant applications, not only do you have the dimensional requirements, but the cosmetic requirements are equally important, because you don’t want any points of failure in the tube. If the implant is in a person’s back, imagine how many times a person bends back and forth every day, and how that is going to affect the material over a period of 30 years,” he said.
Today’s Materials Offer Better Performance
As tubing is called on to perform more complex functions, greater demand emerges for materials that provide long-term durability, biocompatibility and various specific surface tasks. An example of the latter requirement is the degree of smoothness of the tube’s outer material, which is integral in vascular applications, in which the tube will be snaking through delicate veins and arteries.
Established in 1987, Tampa FL-based MicroLumen, Inc. manufactures high-performance Polyimide tubing. Polyimide is a thermoset plastic that possess many highly sought after characteristics.
“No other plastic has the same kind of properties,” explained Krissi Heard, technical salesperson for the company. “Our plastic can withstand gamma. Some of the other plastics, after so many doses of gamma, will begin to deteriorate. You can put acids or very alkaline solvents on it and it will not deteriorate. It can be exposed to 400-degree heat and it won’t melt. Even on the surface of the sun it wouldn’t melt. It would only turn to ash.”
The material also possesses desirable mechanical properties, Heard added. It is flexible yet transmits torque very well. It also offers a high degree of kink resistance, even when the tube has extremely thin walls. This quality is important, because Polymide tubing can be manufactured to extraordinarily small sizes. The sizes range from .004 inch—the width of a single strand of hair—to .086 inch—the width of a coffee stirrer. Coffee stirrer diameter is about as large as MicroLumen’s tubes get, according to Heard.
The only caveat with Polymide is it tends to be a little more expensive than other plastics. But when designers are looking for tubes for use in very critical applications, they are more than willing to pay for top-quality materials. MicroLumen certainly is not pounding the pavement for clients. Business is so brisk that the company has expanded from eight employees to 50 in just the last decade.
This seems to be true across the board in the tubing market. If a shop can provide a quality product and deliver it on time, price is not as important a consideration, according to Bob Poirier, vice president of sales at Manchester NH-based Dunn Industries, Inc., which specializes in extrusion for the medical, aerospace and telecom industries, and has a reputation for manufacturing superior tubing. “We look at our quality level and our delivery time. Most of the time, price is not the whole decision criteria. It is delivery time and quality that matter most,” Poirer said.
Design engineers are always searching for the next material breakthrough. Whether it is a nylon or polyurethane material, design engineers are constantly looking for increased performance and bio-stability. There are several smaller resin manufacturers that are trying to promote their resins for use in medical devices. ExtruMed has been successful in structuring strategic alliances with some of these companies. Lathiya noted, “Whenever you can educate a customer, from a chemistry and processing standpoint, on different resins that may work for their application that is truly value-adding information.”
In addition to polymers, there also is a place for metals in the world of tubing. Metal tubes often are used in applications in which a high degree of force or push is necessary, such as in angioplasty. To guide a catheter through an artery and past possibly dense lesions, surgeons must use some muscle, which increases the risk of kinks in the tube. Kinks can both harm the patient and decrease the efficacy of the procedure. One market leader producing metal tubing is Creganna Medical Devices, with manufacturing facilities in Galway, Ireland and Marlborough, MA and offices in Minneapolis, MN; San Diego, CA; and Finland. The company’s recently launched PoleVault hypotube has been gaining a reputation for quality due to its extreme kink resistance, estimated to be up to 40% better than any other hypotube on the market, according to Creganna.
Although known for its metal products, Creganna has moved into extruded and braided materials as well, according to Product Manager Maura Leahy. Much of this work is done at the company’s Marlborough facility. Unlike most tubing manufacturers, which tend to be mainly production oriented, Creganna has a reputation as a design house, Leahy said.
“Four years ago we established a contract design service as a standalone business unit within Creganna. We have had amazing market success with that," said Leahy. The company gets substantial business from manufacturers of minimally invasive devices for vasculature applications such as the peripheral vasculature or neuro-vasculature. These companies need an advanced tubular-based device to deliver their products into the body. “For example, carotid artery stents, or self-expanding stents,” she explained. “Device manufacturers continue to push the frontiers of minimally invasive treatments by seeking to treat ever more complex and hard-to-reach anatomy. This is driving demand for more sophisticated and innovative component level products. Our contract design service clients often do not even bother designing a delivery system. Instead, they focus their design efforts on the treatment device and task Creganna's designers to create the delivery system from the ground up.”
Consolidation Permeates Tubing Markets
As more business and venture capital flow into tubing manufacturing, some shops have become overwhelmed with the intense new demands and have opted to sell out, while others, flush with earnings, have decided to buy them. “I think we will continue to see further consolidation in the industry, as some of the smaller extrusion companies will have to make the choice of either heavily investing in their business or becoming part of a larger organization that already has the quality, engineering, sales and finance infrastructure in place,” said Lathiya. “That is exactly what happened to us. We were a small family-run business. Then we were acquired by a group of investors, and subsequently went on to acquire our biggest competitor. Over the past couple of years, we have invested heavily in our quality department, engineering, finance, sales and marketing—we recruited people with relevant industry experience to build out our organization. The smaller companies may not choose to make those investments as it effects profitability in the short term. However the landscape is changing. Customers are demanding more from their suppliers and in the long term if companies want to continue to grow they will either have to make these investments, sell their business or stay small.”
Creganna is experiencing similar growth. It purchased a tubing company last year and always is on the lookout for future acquisitions, according to Leahy. “If you assess the baseline market, there has been enormous growth in recent years. The advent of DES [drug-eluting stents] two or three years ago really brought the market to a whole new level…It’s a hugely exciting industry to be working in.”
Neurostimulation: A Growing Market for Precision Tubing Manufacturers
For certain patients with chronic pain, life is all but intolerable. Conditions such as failed back syndrome, complex regional pain syndrome and arachnoiditis can leave sufferers bedridden and in a state of continual torment. In some extremely severe cases of chronic pain, no amount of even the strongest pain medication can alleviate the patient’s misery.
Growing numbers of these patients are gaining some relief from a new technology called neurostimulation. In neurostimulation, an implant in the spine or peripheral nerves delivers a low-voltage shock that blocks the sensation of pain. The mechanism of action is unclear, but experts believe these low-grade shocks somehow stimulate the body’s pain inhibitory system. Instead of feeling pain, the patient experiences a tingling sensation akin to a limb that “falls asleep” after being deprived of blood flow, which is called paresthesia.
Studies have demonstrated that when implanted in carefully selected recipients, neurostimulation devices reduce pain, increase activity levels and reduce dependence on narcotic painkillers. In addition to its apparent efficacy and adequate safety profile, interest in this technology is being driven by advances in low-power semiconductor designs that prolong battery life; wireless communication innovations associated with the FDA-created band of frequencies known as the Medical Implant Communication Service; and, perhaps most significantly, the wide range of other conditions it potentially could treat. Migraine headaches, stroke recovery, Alzheimer’s disease, obesity, epilepsy and depression are under investigation as potential targets of neurostimulation.
“This is a fast growing market for us,” said Apur V. Lathiya, chief operating officer for Placentia, CA-based ExtruMed, one of the industry’s largest manufacturers of custom thermoplastic medical tubing. “It is essentially the same technology as a pacemaker. An electrical stimulus is provided through coils and electrodes. The lead tubing functions in two capacities: as an insulating jacket for the active lead wires and receptors, which deliver the electrical stimulus and administer the therapy, and as a long-term bio-stable interface with the body.”
Plenty of companies can provide tubing to an OEM or a venture capital funded startup, but fewer can provide implantable quality tubing, the kind designed to stay in the body for 30 or 40 years without malfunctioning. This is an area where ExtruMed sees itself as a market leader. “We are saying, not only do we do this, but it constitutes a significant level of our business. We are the only company that services all three major OEMs in both neurostimulation and cardiac implant tubing,” said Lathiya.