Testing of Catheters

Testing of Cardiovascular and Urological Catheters

Zwick offers the ideal testing systems for catheters—medical devices that belong to the highest risk category and are subject to strict quality requirements.
Catheter test heart model underwater image

Horizontal Testing of Catheter Systems

Catheters are used for many reasons, including transporting microinstruments integrated in a patient's body. They enable surgeons to make surgical procedures as minimally invasive as possible. A catheter can also help administer medicine directly to the infected area of the body or facilitate the use of stents to keep blood vessels open.

Engineers who develop these catheter systems and guide wires focus on reducing the coefficients of friction and breakaway torques. Zwick's horizontal AllroundLine testing machine makes it possible to determine the push force in a simulated catheter insertion with very high accuracy. The frictional behavior of the catheter is measured by pushing it through an artificial artery. This is known as the tortuous path. The test is carried out in a horizontal orientation to simulate the physiological status of the patient during surgery.

Zwick has developed a system specifically for this application that controls both the crosshead of the materials testing machine and a specially automated specimen grip. The horizontal AllroundLine testing machine provides space for 3D models and fluid baths above and below the main test axis. In a typical test, the machine pushes the catheter into the artificial aorta for a predefined distance. The specimen is then released and the crosshead returns to its initial position. The pneumatic specimen grips close again and the crosshead moves in the direction of the test. This sequence repeats itself until the catheter is completely inserted in the artificial artery. The fully automated test method makes it easy to test artificial aortas of various lengths. The following results can be determined with the machine software:

  • Insertion force measurement: measures the force used to advance through the introducer sheath
  • Track force: measures the force required to advance the catheter, guide wire, or another minimally invasive instrument through the artificial artery
  • Push efficiency: uses the proximal and distal load cell to measure the amount of force the distal tip of the product sees when a known force is being applied to the product on the proximal end
  • Guide wire movement: measures the force needed to advance a guide wire through a catheter, a guide catheter, or a similar minimally invasive instrument
  • Flexibility: measures a catheter tip's ability to track over a specified bend in a guide wire, such as 90 degrees
  • Guide wire and catheter lubricity track measurement: comparative test using the track test data to determine if coatings have an affect on the force required to advance product through an artificial artery

The results can be determined with a high level of accuracy. The extremely stiff load frame with digital control and drive systems is able to ensure that forces measured during the test originate from the sample under test and not from within the machine itself. The machine's control system has such a high resolution that it is able to position the crosshead of the machine to less than 1µm, and read forces to an accuracy of better than 0.5 % down to values of less than 0.1 mN.

Stent fixture
Catheter test horizontal heart model
Horizontal catheter testing

Testing the Lubricity Track Force of Catheters

Catheter glide force test in fluid bath
The coefficient of friction of cardiovascular and urological catheters must be tested when they are wet. To do this, the catheter is removed from a temperature-controlled water bath through jaws which are closed with a defined gripping force. These jaws can be opened and closed automatically to produce a repeated cyclic test. In addition, the jaws can be changed quickly to facilitate various lubricity surfaces for tests.

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Glide force test on catheters

Glide force test on urological and cardiovascular catheters with thermoregulation bath

Testing of Catheter Systems

To determine the insertion and connecting forces of catheter tube systems in accordance with DIN EN ISO 10555, each individual connector must be loaded to tensile until failure. For this, a wide variety of connecting diameters are required. The 8050 self-aligning tension grip has a rotating self-locking disc with various opening widths used to test numerous connectors. Pneumatic specimen grips for maximum tensile forces up to 1 kN are used for repeatable gripping of the opposing side of the catheter. The specimen grips are closed by means of a foot pedal, leaving both hands free for inserting the specimen. The closing force can be set steplessly with the pneumatic control unit, and the low overall height of the specimen grips facilitates optimal use of the material testing machine's test area. In addition, Zwick offers a wide range of jaws for the most diverse types of applications.
Tensile test catheter systems ISO 10555 turret specimen grips
Tensile test catheters ISO 10555 turret specimen grips

Benefits and features:

  • Disc-locking feature enables tool-free changes between test environments
  • Generous grip height enables testing of large specimens (for example, needle pull-out tests on syringes)
  • The 8050 specimen grip can be used with any materials testing machine using Zwick's standard connector system.
  • Easy changeover to additional rotating discs

Flexure Tests on Guide Wires, Catheters, and Tubes

Flexure test to determine the kink resistance of guide wires
2-point flexure test to determine the kink resistance of guide wires. The test fixture is designed for forces up to 50 N. The grip-to-grip separation can be adjusted steplessly. In addition, the fixture is equipped with a dial gage to display the grip-to-grip separation of 0 to 55 mm, with an accuracy of 0.1 mm. It has rotatable clamping, with specimen clamping in the vertical plane. The bending angle (max. 90°) is generated via the rotating clamping unit.
Flexure test kit for stiff medical catheters and hoses
Another flexure test kit for testing the flexure characteristics of stiff medical tubes (catheters, etc.) and guide wires, consists of a flexure table and two holding-down clamps for gripping the specimen. Differing specimen diameters are accommodated by differently-shaped holding down clamps (straight and prismatic), which are easily exchanged. The kit is designed for a maximum compression force of 50 N.
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