How miniaturization is transforming peelable heat shrink tubing (PHST) technologies

The future of the medical tubing sector is an interesting one, not least because there are a variety of pressures on organisations within this space to provide cost-effective, highest quality products in shorter timescales. This is mainly driven by the global healthcare market, which continues to demand products and solutions that push the boundaries of what is possible at a price point that is highly competitive.

Take the catheter market as a prime example of these challenges. In the world of neurovascular techniques, clinicians are pushing for solutions that enable them to deliver complex procedures more efficiently, therefore not only reducing costs both in terms of time and money, but also enabling the provision of a higher quality of care to patients. Procedures which include delivering stents, coils and in some cases even signals/therapy down the catheter are all techniques that have improved with technological advances and are becoming mainstream.


The evolution of peelable heat shrink tubing

The peelable heat shrink tubing (PHST) market is an exciting area to be in. Not only does it address healthcare customers’ unmet needs, but it also paves the way for progressively smaller catheter-based procedures – an on-going requirement for medical device manufacturers. The reasons, aside from their desire to meet the healthcare sector’s needs, are because PHST ultimately reduces total cost of ownership (TCO) for the catheter manufacturer. Since companies no longer have to use the process of skiving the heat shrink material from the catheter, PHST can help them produce the final product more rapidly with improved yields and lower inspection levels while being more ergonomically safe.

The peelable heat shrinking process requires a very specific set of tasks, using typically, the products listed which include a mandrel, Etched PTFE liner (EPL), a sleeve of braiding, a tube of Pebax, PHST and a laminator. Having stretched the EPL liner over the mandrel and tied a knot on both ends, the catheter manufacturer should then place it into a vertical laminator, with a heating chuck on the top and a weight on the bottom enabling a consistent amount of heating and stretching. An important consideration for catheter manufacturers at this stage is the tensile strength of the EPL. With Junkosha’s EPL liners, they are processed to deliver consistent high tensile strength, which compares favorably to competitors.

On completion of this first stage, the etched PTFE Lined mandrel is taken out of the laminator where first the sleeve of metal braiding is placed over the liner (this delivers tortuosity to the surgeon in helping to snake the catheter around the body to get to the vessel or segment required with ease) followed by the tube of Pebax and then lastly, the PHST. The next stage is to place all of this in to the laminator, where the PHST enables the reflow of all of the materials used into one continuous, robust, tube. Once completed, the catheter manufacturer can peel off the PHST with ease, neck the mandrel and pull it out.


Peelable Heat Shrink Tubing takes small to the next level

The latest innovations from a PHST perspective answer the call for options that enable miniaturized catheter-based procedures. They include ultra-small PHST and high-shrink ratio PHST. The ultra-small PHST is the only suitable tubing for laminating jacket coatings to tiny guide wires, for example 0.011” and 0.014”, leveraging the fact that PHST has a recovered ID down to 0.009”. These miniature guide wires are suited for navigating vessels to reach a lesion or vessel segment within the brain or heart. The high-shrink ratio PHST (2:1) can be employed in manufacturing processes where tapered microcatheter shafts are used or where tolerance take-up is an issue.

A key benefit of PHST is that it can reduce scrap rates and decrease assembly time. Requiring only a single slit in one end to get it started, PHST peels easily along its entire length without the need for extra tools in the process, therefore saving significant time over the removal of fluorinated ethylene propylene heat shrink tubing (FEP-HST). In addition, it enhances productivity for catheter manufacturers who can remove the PHST with ease without damaging the catheter or guide wire, therefore resulting in an ability to use the same catheter more frequently.


The move towards miniaturization

The move towards miniaturization, from a medical tubing perspective is picking up pace, with medical device manufacturers demanding catheter solutions that can readily penetrate harder to reach places. Added to this is the requirement for increasingly sophisticated catheters that can send diagnostic signals into the body or provide therapy, in other words ‘active’ catheters.

The trend towards miniaturization of catheters covers a wide spectrum of applications including, as mentioned, neurovascular delivery of devices such as coils and stents for stroke or aneurysm therapies, and even signals/energy to help support treatments such as neuro modulation or neuro stimulation in the case of research for treatment of Parkinson’s disease.

Further innovations in the field of active catheters, which are designed to provide conduits for the delivery of signals or energy, are for example Intra Vascular Ultra Sound (IVUS). This is characterized by diagnostic applications such as intravenous examination of atherosclerosis, a condition in which fatty material collects along the walls of arteries, with the distal end providing signals back to data collection equipment. Alternatively, therapeutic applications involve pulsed ultrasound to remove plaque, and a transcranial MRI-guided High Intensity Focused Ultrasound (HIFU) system for the non-invasive treatment of various brain diseases such as brain cancer and Parkinson’s disease (thermal ultrasound), and stroke (mechanical ultrasound using microbubbles).

Peripheral arterial disease, where plaque builds up in arteries in the legs and in other places preventing blood flow, is usually treated using balloon angioplasty and stents, if a procedure is called for. A recent device, pioneered by Fremont-based Shockwave Medical, combines lithotripsy — which uses sound waves to break up calcium and is often used to treat patients with kidney stones — with the commonly used angioplasty balloon catheter. The Lithoplasty System was cleared by the FDA for use in the treatment of peripheral artery disease (PAD) in the US, where one in 20 individuals over the age of 50 has PAD.


Enabling catheter innovations

The miniaturization of catheters including the growing use of active catheters is challenging the medical device sector worldwide to produce solutions that enhance their use in previously inaccessible areas of the body. New tools, such as PHST, are cost-effective in reducing scrap rates whilst also increasing throughput by shortening assembly times. In the future, PHST might become a requirement for such technological advances.