Manufacturers must test medical devices to detect flaws that could lead to catastrophic failure in the field as well as ensure that the devices will function efficiently and meet end-user requirements.

Instruments that perform tests on medical devices must work reliably and repeatability. They must be cost effective, operator-friendly, and time-efficient. Often, these requirements cannot be met with an off-the-shelf instrument.

Consider, for example, the testing of medical catheters as a good example. In its simplest form, a catheter is simply a tube with a connector at one end through which a medium is passed. Testing just takes blowing into one end and making sure air comes out the other end, right? Of course, it’s not that simple. Catheters must be tested for two different failure modes using two methods, leak testing, and flow occlusion testing. Leak testing ensures that the test medium applied to one end of the catheter is not flowing out of a connector or a flaw in the material. Flow occlusion testing ensures that the test medium exits the device at the same rate it is applied. This shows that there is no obstruction in the catheter. In addition, because some catheters in end use are subjected to high pressures, manufacturers must quantify the pressure used in tests and the flow rate. Finally, manufacturers must securely store and maintain test results in case the government comes calling.

Catheters are seldom as simple as just described. They often include multiple lumens, or tubes, which are extruded individually and together comprise the flexible catheter body. Each lumen has a defined function, and it is necessary to ensure the integrity (freedom from interlumenary leakage or leakage at welded joints) and the patency (the open and unobstructed nature) of each lumen. Most lumens have a port at the distal tip or the sides of the catheter, pass through a connector body, and connect separately at the proximal end to a device or devices. Each lumen must be tested separately. It’s also helpful if failures can be attributed to specific lumens.

To refine the problem a bit more, the lumens in question may or may not be identically sized or made from varying materials. Because leak testing is volume related, it might be necessary to use different failure criteria for the lumens in a single catheter. Additionally, tests must be timely so manufacturers can catch process-control problems early-on.

For testing catheters, we developed the TME Solution Leak/Flow Tester with custom fixturing. The Solution is a high-resolution (0.0001 psig), programmable instrument that can accommodate catheters made up of one to eight lumens. Individual test ports interface with proximal luer inputs or straight tubes. The instrument lets users program different failure parameters for lumens with different specifications (although the test pressure must be consistent throughout).

The key to the instrument lies in the fixture design. The fixture, operated remotely by the test instrument, usually consists of a radial seal (to hold the catheter body in place) and a “stop” that opens the tip to the atmosphere for the flow-occlusion test. Once patency has been established, the fixture blocks the distal tip (for the pressure decay leak test). Seal clamps located along the fixture axis similarly open and block any side ports. Once the catheter sits in the fixture with the proximal connectors attached to the test instrument’s front ports, the TME Solution automatically and sequentially tests the lumens for flow and then leak, clearly identifies failures and their cause (leak or occlusion), reports results by lumen, and stores the data. In most cases, the test time takes five to 10 seconds.

When process time is highly important, a dual switching system is available that tests one catheter while the operator unloads and replaces the tested part. The test instrument automatically switches to the second catheter while the operator works.

Separate fixtures for a variety of catheters can be used interchangeably with the TME Solution, which can store up to 100 test programs. It conforms to ASTM guidelines and meets 21 CFR Part 11 data protection.