Medical Design Briefs - July 2023 - 8

Optimal Hypotube Design
Pushability. Pushability is
determined by the measure of
the transmission of longitudinal
forces from the proximal
to the distal end of the catheter.
Ideally, when a pushing
force is applied by the physician,
an equal movement of
force should be exhibited on
the distal tip inside the patient.
When transmission forces are
high, the physician navigates
with confidence, knowing that
precise movements to the
proximal shaft will translate to
precise movements within delicate
anatomical pathways or
structures, for example, within the crucial
anastomotic circle of Willis structure
during neurovascular navigation.
Trackability. The term trackability is
therapies. Inflation and deflation
times describe the
When designing a hypotube, optimization of one characteristic can impact others to
achieve the perfect balance for the product. (Credit: Freudenberg Medical)
Kink Resistance. Intravascular anatomy
is challenging to navigate and reused
to measure the overall ability of a device
to progress through complex vasculatures
and reach the treatment site. Sometimes,
a physician will refer to trackability
as the overall feel of the device or how
smoothly it responds to the physician's
manipulation. When low tracking forces
are present, the physician feels that the
device is easier to manipulate and position.
The distal, or treatment end of the
catheter, plays a crucial role in overall
trackability. Advanced processing technologies
can make the distal end of the catheter
more flexible, thus aiding trackability.
Flexibility. Flexibility is a measure of the
stiffness along the hypotube length and is
a critical part of the overall catheter design.
Flexibility is a major contributor to
the trackability or feel of the device and,
while high pushability or stiffness is desirable,
a well-designed hypotube should
simultaneously exhibit good flexibility
when it is required to navigate acute angles
or anatomical structures. Optimizing
flexibility and pushability together is key
to the perfect hypotube design.
Lubricity. Lubricity measures how
much the friction between the medical
device and the anatomy or companion device
is reduced through the application of
a coating to the metal hypotube. Freudenberg
Medical, for example, offers a differentiated
coating solution called Cambus
Coat™, which has proven to exhibit excellent
adhesion and resistance to flaking
under the most demanding performance
tests. Additionally, Cambus Coat™ is a
smooth lubricious coating solution ideal
for hypotube and guidewire applications.
8
quires the physician, on occasion, to
cross acute radii. Kink resistance measures
the hypotube's ability to maintain
an intact cross functional profile when
bent around a radius. This characteristic
is critical in preserving the patency of the
internal lumen which plays a critical role
in therapy delivery. With this criticality in
mind, an advanced metallurgical solution
with superior kink resistance over
traditional 304 stainless steel hypotube
constructions such as Freudenberg Medical's
E-Pro™ should be considered. In
addition, such a solution offers product
designers an opportunity to optimize internal
diameters.
Inflation and Deflation Time. In addition
to being a critical tool in vascular
navigation, the hypotube plays an essential
role in delivering balloon catheter
length of time it takes an angioplasty
balloon to activate
and deactivate. When inflated,
a balloon creates a
temporary restriction of
blood flow, which can be
damaging to downstream
anatomy unless it is precisely
and accurately controlled.
The inner diameter of the
hypotube plays a crucial role
in determining the balloon
inflation and deflation time.
In short, the larger the internal
diameter of the hypotube,
the faster balloon inflation and
deflation response.
Manufacturing the Optimal Hypotube
An extensive range of capabilities are
required to manufacture the optimal hypotube,
balancing the performance characteristics
discussed above. This section
reviews the key technical capabilities required
to deliver a tailor-made minimally
invasive catheter.
Electrical Discharge Machining (EDM).
EDM is a high-precision machining process
used for cutting precision contours in
metal material. This method produces
burr-free skives in thin-wall tubing. A
well-designed skive enables a smooth transition
zone between the metal shaft and the
distal balloon assembly, improving overall
trackability and flexibility of the catheter.
Laser Cutting. Hypotubes must navigate
complex and tortuous paths, thereA
hypotube provides essential performance characteristics to enable access and delivery within the vasculature.
Its characteristics translate to the physician experience when deploying a catheter within the patient.
www.medicaldesignbriefs.com
Medical Design Briefs, July 2023

http://www.medicaldesignbriefs.com

Medical Design Briefs - July 2023

Table of Contents for the Digital Edition of Medical Design Briefs - July 2023