Connections in medical devices encompass a variety of styles, including those that make electrical connections within medical machines and systems, as well as those used to latch and unlatch tubing in medical devices. Connectors are used to transfer power, signal, data or media and can be designed for just one of these operations or as hybrid systems. No matter what type, they must all be safe and hygienic.
Electrical medical connectors and cables are often used in MRI, ultrasound, defibrillators, EKG, heart-lung machines, surgical, diagnostic and therapy systems, to name a few. As a result, reliability is critical. These connectors must be easy for trained professionals to use and connect and disconnect, but also fool-proof to prevent untrained users from damaging or mating cables incorrectly.
In addition to being IP68-rated for watertight sealing, most reusable connectors (those used in operating rooms or similar environments) must be autoclavable, surviving temperatures above 121° C for 20 minutes. If not, they must be inexpensive enough to be disposed after a single use. Common materials are different types of plastics (PEEK, PVC, etc.) and stainless steel.
Some medical connections require high numbers of mating cycles, from 5,000 cycles or more, such as an ultrasound machine where the operator changes the cable many times during the day. Medical connector manufacturers have developed specific mating contact systems to accommodate many mating cycles.
Most connectors in medical applications feature a push-pull locking mechanism that prevents accidental disconnection if someone trips or runs over a cable. Because many designs are custom or semi-custom, a variety of contacts are available, ranging anywhere from male and female solder, crimp and PCB termination to multipole 2 to 64 contacts.
Medical cables are usually very flexible. The key to flexibility is the use of small conductors using stranded wire and dielectric recipes optimized for flexibility. Over-molded cables help maintain this flexibility while providing a seal against moisture and strain relief and preventing mismating and latching.
The operative demands of your application determine the parameters for tubing and connectors. Fittings, luers and quick disconnect couplings are the most common tubing connectors used in low-pressure environments. They are reliable, cost-efficient, low-weight designs and should be designed to reduce or even eliminate the potential for user fault. Hybrid connector designs help transfer liquid and air media, as well as electrical signals, in one device. While each is appropriate for certain applications, they are not necessarily interchangeable. For example, in applications where spill prevention is desired, a valved connector is a better choice than a luer (see figures 1 and 2). If the application involves frequent connecting and disconnecting, a quick disconnect designed for long-term reliability is a good choice.
These latch and unlatch couplings and fittings used on medical equipment are often of the quick-disconnect design, allowing for quick and secure connections and disconnections. They are used to prevent accidental misconnections for safe machine and system designs.
Designs include general-purpose couplings for air and fluid handling to simplify design with a modular approach and non-spill features. Next, connectors made with medical-grade materials meet USP Class VI, MEM elution and other regulations. They must also be safe and clean designs that allow for easy connections. Finally, several manufacturers provide specific connectors for applications such as blood pressure machines.
It is important to consider the following when selecting a connector for use in medical applications, as these factors will all impact your choice:
- tubing size, both inner and outer diameter
- termination type, including hose barb, compression fittings and push-to-connect
- flow rate and pressure,
- ID size for hose barbs, OD for push-in fittings and tube ID and OD for compression
- valve designs, such as integral valves, flush-face designs, poppet-style, etc.
- mounting and configuration, such as panel mount or direct mounting into NPT thread or ports
- connector quality—even the most minute defect or jagged edge could lead to leaks or tears in other materials.
Finally, connector materials used must also be considered, as a variety of fluids and gases are used in medical applications and the fluid must be compatible with the thermoplastics, fluoropolymers, metal alloys and sealing materials.