Because the stakes are high and the options are many, it’s important to have a simple and repeatable process for selecting how you will connect tubing in medical applications. We have developed a four-step process based on these simple questions:
1. What are the safety needs of the device or equipment?
This is the most important question you can ask about the connector. Not only does it need to be safe for patients, consideration needs to be given to the health care professional who will be using it.
One of the primary concerns is misconnections. As the number of tubes and connections in medical laboratories, hospital rooms and operating rooms continues to increase, so too does the potential for misconnections. This is especially a problem when using a luer as a connector.
In fact, the problem of misconnection is concerning enough that the International Standards Organization (ISO) has released a series of new, small-bore medical connector standards. Specifically, ISO 80369-1 contains general requirements to ensure the prevention of misconnection between small-bore connectors used in different applications. It is important to work with a company who has developed products to answer misconnection concerns.
2. What are the functional needs of the application?
The selection parameters for tubing and connectors is driven by the functional needs of the application. Consider the following factors as part of your decision-making process:
Flow requirements: The inner diameter size of the tubing helps establish the size of the connector. But consideration must also be given to pressure drops across connectors and valves. These can vary greatly by manufacturer, and some designs exhibit less turbulence and resistance to flow than others. By comparing published CV factors for various connectors (often listed in manufacturers’ catalogs), design engineers can determine the pressure drop across the connector and match the correct size to their application requirements.
Media effects: Connectors need to be compatible with the media being transferred. Start with a review of published data in chemical compatibility charts. Also remember to consider cleaning solutions and other environmental exposure including the effects of gamma ray, electron beam, ETO or autoclave sterilization on connector materials if the device will be sterilized.
Temperature and pressure: Consider the range of temperatures and pressures in the application. Also consider the range of temperatures the connectors might be subjected to in storage or during shipping.
Connector quality: Manufacturing quality of a connector dramatically affects its performance and can also play a role in aesthetics. On molded plastic couplings, imperfections on barbs or threads can lead to leaks. Check the parting lines (where two halves of the mold came together) and inspect for mold defects—they should be minimal on the connector body and absent from the first hose barb. The connector should be free of jagged edges that can catch or tear surgical gloves or tubing.
Fitting type: The most popular styles are single and multiple hose barbs. Single hose barbs are sufficient with softer tubing such as silicone rubber. However, connectors with multiple, sharp barbs provide a more secure connection over a wider range of tubing types.
Valve options: Connectors with integral valves prevent spills upon disconnection and prevent air from entering the system. Connectors with integral precision flush-face valves are considered true “dry-break” connectors and should be selected when there is a critical need to avoid any drips, spills, contamination or the introduction of air.
Mounting options: In some applications, a connector is mounted to the back, side or front panel of a machine. Metal may be preferred for strength and a higher-end appearance; however, in most applications, plastic provides a robust, cost-effective solution.
3. Will an enhanced connector improve its functionality?
Communicating couplers can transmit information that helps protect equipment, improves processes and even saves lives in medical applications. These intelligent connectors are equipped with radio frequency identification (RFID) technology allow data to be exchanged at the point of connection. They communicate by sending RFID signals between the two separated coupling halves. Data is stored on an RFID tag embedded in the passive half of the coupling, known as the insert. Looking for the tag is an RFID reader housed in the active half of the coupling, called the body. When the two coupling halves are brought within a few centimeters of each other, the reader detects the tag, reads it, and sends the tag data to the control unit running the system. The control unit can also tell the reader to write new information to the tag.
You may also want to consider a hybrid quick disconnect, which combines the transfer of power, signal and fluids (liquids and air) in a single device. Hybrid connectors eliminate the need for multiple connections and simplify the user interface between remote tools and a device. These connectors allow technicians to quickly and safely change or replace modular tools, umbilicals or hand pieces.
4. What connector material works best with the application?
The type of media flowing through a connector influences what material the connector is made of. Here’s an overview of the most widely-used materials:
BS – Economical, medical-grade thermoplastic that withstands gamma and E-beam sterilization.
Acetal – Strong, lightweight and economical material that has good rigidity over a broad temperature range, with toughness and durability.
Polyamide (nylon) – Very resistant to wear and abrasion, with good mechanical properties at elevated temperatures.
PEEK (polyetheretherketone) – An engineered thermoplastic with high-temperature, chemical and fatigue resistance.
Polycarbonate – Resistant to some chemicals, transparent and withstands sterilization for medical applications.
Polyethylene – Low-cost, chemically resistant, opaque thermoplastic.
Polypropylene – Excellent general-purpose resin that is highly resistant to attack from solvents and other chemicals.
Polysulfone – Rigid, strong and chemically resistant, it withstands repeated sterilization and higher temperatures more than other thermoplastics.
PVDF (polyvinylidene difluoride) – Rigid, strong and chemically resistant, it withstands repeated sterilization and higher temperatures better than other thermoplastics.
Aluminum – Lightweight metal with a high strength-to-weight ratio that is available with a durable anodized finish.
Chrome-plated brass – Rugged and attractive, this metal is excellent for high-pressure and high-temperature applications.
Die-cast zinc – Weighing about 20 percent less than brass, this durable and lightweight material withstands high pressure and high temperature.
Buna-N – This is the most common O-ring material due to its solvent, oil and water resistance.
EPDM (ethylene-propylene-diene-monomer rubber) – Also known as EPR, this material offers excellent chemical resistance.
FKM (fluorocarbon) – Known for its outstanding resistance to heat, oxidation, weathering and ozone.
Silicone – Has good temperature resistance. Medical-grade silicones also meet FDA Class VI requirements for biocompatibility in life-science applications.
Connector selection is an important decision in the design process because it helps fulfill aesthetic goals as well as product performance and patient safety objectives. Considering the key attributes of the connector early helps make the medical device easy to use and plays a key role in overall perception of the device’s design.
*CPC does not specify the suitability of any connector for a particular medical application.