Company insight
Component selection criteria in medical devices
For most medical device design engineers, selecting components from multiple vendors is a critical step in the design process. Whether the components and tubing are inside the device or part of a disposable tube set, there are many different criteria that should be considered in the selection process. This article by Qosina will provide guidelines on where to look when searching for the right components for the operations needed.
epending on the type of medical device, there can be quite a bit of tubing, connectors, pumps, fluid regulators and other fluid management sub-systems. Each section of tubing, connections and pumps completes a task for fluid or air flow inside of the device. These can be found in medical devices such as ventilators, in-vitro diagnostic devices, dialysis devices, blood pump systems, etc. Selecting the appropriate tubing and connector components can make a significant difference in device performance and manufacturability. Tubing is often necessary to keep fluid or air moving. Tubing selection factors include durometer, ID/OD and wall thickness, connection to pumps or tubing connectors and fluid paths within the medical device. For example, tubing must often be worked around other sub- systems within the device. This means the designer must be careful not to place tubing in a position where it could kink within the device. The durometer and thickness of the tubing can help reduce the potential for kinks. In addition, tubing needs to be selected based on rigidity, chemical resistance and fluid flow dynamics. Assembly of the tubing with the pumps and connectors within the device is critical to the production teams that need to consistently assemble the full device for performance to design specifications.
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Connectors on the inside of the device are utilised to connect tubing from multiple subassemblies in order to support functional performance in the device. The connectors chosen must be easily assembled to the tubing but also ensure a robust connection, preventing leaks. Often, connectors used internally
in medical devices are either barbed (inserted in the tube), compression (holds the outside of the tube) or bond-in (glued/bonded to the outside of the tube). Connectors are chosen to pass fluid or air and to control the flow of fluid or air backward and forward. This may be handled by standard open-flow connectors, check valves and filters. Check valves control forward flow and limit back flow of fluid. Filters limit the type of fluid flowing and remove any particulate that should not continue to flow forward in the device.
Tubing in medical devices are vital for keeping fluid or air moving, and must be carefully maintained. for the application.
Medical device designers do extensive prototyping of subassemblies in laboratories. This way, tubing and connector options can be tested to ensure the best design for manufacturability and performance. Different types of pumps and flow control devices can be tested to make sure that tubing and connectors are chosen to optimise the best fluid control
Medical Device Developments /
www.nsmedicaldevices.com
Cost is typically not a major factor when selecting tubing and connectors for the inside operations of a medical device. This is because the volumes required are usually low, and the surrounding mechanical systems are significantly more expensive. The primary goal is to ensure that operations within the device are maximised to the specifications. Special attention is needed to keep the device easy to assemble and allow for quality checks to ensure consistent performance. Typically, tubing and connectors used outside of the medical device get a lot more attention. This is because these tube sets are the single-use side of the device and generate the most revenue for the medical OEM. External medical device tube sets are related to devices such as infusion pumps, suction/irrigation for surgery, blood transfusion, dialysis and ophthalmic surgery. These are only a
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