Medical tubing connectors
Choosing the right fluid connector can improve patient safety and user convenience, while maximizing sealing and flow performance written by Dr. Hasanat Alamgir.
Because of the many risks and options for connecting tubing in medical applications, it is important to choose a simple and repeatable strategy to select the best connector. The process requires a thorough analysis of the application to ensure that the connector is compatible with the physical, chemical, and biological environment, is easy to use, and helps prevent misconnections-whether the application involves connecting the trachea for the blood pressure cuff, the reagent supply Connect to a blood analyzer or establish a critical connection between the patient and the heart-lung machine. The connector selection process can be divided into the decision steps outlined below.
Connectors for medical applications come in a variety of styles and sizes. Choose the style that provides the best performance, convenience and safety.
Step 1: Consider security requirements
Start choosing a connector by considering the safety of the patients and healthcare professionals who will use the connector. The connector must be easy to use and intuitive, so there is no risk of leakage, overflow or especially connection errors.
In the past, the Luer connector was a simple universal design that provided acceptable connections for many applications. However, the number of pipes and connections in medical laboratories, hospital wards, and operating rooms continues to increase, increasing the risk of connection errors. Regulatory and reporting groups such as the Food and Drug Administration (FDA), the Institute for Safe Use of Medicines (ISMP), and the Joint Committee (TJC) have all reported injuries or deaths of patients due to connection errors.
Concerned about the proliferation of luer connectors, the working groups of the International Standards Organization (ISO) and the International Electrotechnical Commission (IEC) are developing a series of new small-bore medical connector standards. The ISO 80369 series of standards will define non-interchangeable connectors and will influence the choice of connectors for a range of medical device applications. As of the beginning of 2014, only Part 1 of the new standard was published; ISO 80369-1 contains general requirements to ensure the prevention of misconnections between small-diameter connectors used in different applications.
Parts 2 to 7 are under development and will provide standards for specific connector applications. ISO 80369-20 will define test methods and is expected to be released in the second half of 2014. At the same time, it is important to cooperate with companies that understand emerging standards and have developed products to solve the misconnection problem.
Step 2: Define the functional requirements of the application
The connection with medical equipment must be safe and convenient, while preventing misconnections.
The connection with medical equipment must be safe and convenient, while preventing misconnections.
The functional requirements of medical device applications determine the parameters of pipes and connectors. The application also specifies whether tubing and connectors are disposable or reusable, and whether valves are required. For example, many hospitals use disposable blood pressure cuffs as a means of controlling infections. For manufacturers of sphygmomanometers and cuffs, this means choosing a connector type without a valve, which is simple, low-cost, and easy to fix and disassemble.
The blood analyzer is a more complex application that uses multiple lengths of tubing and connectors to provide various reagents or cleaning chemicals to the machine. Usually, laboratory technicians connect reagent bottles to the machine through pipes with connectors at both ends. Connectors with valves are designed to eliminate leakage and restrict air from entering the system when disconnected, resulting in a closed system and a cleaner and safer working environment. Finally, the selected connector and pipe materials must be compatible with the reagents, solvents and cleaning agents used.
In the decision-making process, please consider the following factors:
The inner diameter (ID) size of the pipe is usually the primary consideration for connector size. The pressure drop between connectors and valves of different manufacturers varies greatly, and some designs have less turbulence and flow resistance than others. By comparing the published CV coefficients of various connectors (usually listed in the manufacturer’s catalog), design engineers can determine the voltage drop across the connector and match the correct size to their application requirements.
The connector and O-ring must be compatible with the media to be transmitted. First check the published data in the chemical compatibility chart to understand which materials are compatible with the range of chemicals, media or reagents in the application. Remember to consider cleaning solutions and other environmental exposures. Testing potential product materials is always a good idea to evaluate the performance of materials in actual applications. If you want to sterilize the equipment, you should also consider the effect of gamma ray, electron beam, EtO or autoclave sterilization on the connector material.
Please consider the temperature and pressure range in the application, and consider the temperature range that the connector may be subjected to during storage or transportation.
The manufacturing quality level of the connector greatly affects its performance, and it can also play a role in aesthetics. On molded plastic couplings, the parting line on the connector body (the two halves of the mold are put together) and mold defects should be minimized, and the first hose barb does not exist. Defects on the barbs or threads can cause leakage. The gate of the molded connector (where the plastic is injected into the mold) should have no jagged edges, and these tips may jam or tear surgical gloves or tubes.
Types of joints:
The most popular types of hose connections are single-tube and multi-tube barbs. Single hose barbs can be used with softer hoses such as silicone rubber. However, connectors with multiple sharp and well-made barbs have no parting line and can provide safer connections on various types of pipes.
There are many styles of valves, and their flow and pressure drop will be different. The connector with integrated valve prevents splashes when disconnected and prevents air from entering the system. A connector with an integrated precision flush valve is considered a true “dry disconnect” connector. This connector should be selected when there is an urgent need to avoid any overflow, pollution or air introduction during the connection.
In some applications, the connector is mounted on the back, side or front panel of the machine. Metal may be the first choice for strength and high-end appearance; however, in most applications, plastic provides a reliable and economical solution.
Manufacturers provide a variety of fluid connectors so that medical product designers can choose from the best solutions for their applications based on safety considerations, functional requirements, additional performance, and material compatibility.
Step 3: Consider enhanced connector functions
In addition to connecting pipes to facilitate and control fluid flow, the new connector technology can also bring other functional and performance attributes to medical devices and equipment. Smart connectors equipped with radio frequency identification (RFID) technology allow data to be exchanged at the connection point. Smart couplings communicate by sending RFID signals between the two separate coupling halves. The data is stored on an RFID tag embedded in the passive part of the coupler (called an insert). Looking for the tag is an RFID reader located in the active half of the coupler (called the body). When the two half couplings are not more than a few centimeters apart from each other, the reader will detect the tag, read the tag, and then send the tag data to the control unit of the running system. The control unit can also tell the reader to write new information to the tag. Communication couplers can transmit information that helps protect equipment, improve processes and even save lives in medical applications.
Another new connector method to increase connector functionality is the Hybrid Quick Disconnect, which combines the transmission of power, signal and fluid (liquid and air) in a single device. Hybrid connectors eliminate the need for multiple connections and simplify the user interface between remote tools and devices. These connectors enable technicians to quickly and safely replace or replace modular tools, umbilical cords or handpieces.
Step 4: Match the material to the application
The type of media flowing through the connector will affect the choice of connector. The sidebar below lists commonly available connector and O-ring materials and guidelines for using these materials.
Economical, medical-grade thermoplastic that can withstand gamma and electron beam sterilization.
A strong, lightweight and economical material that has good rigidity in a wide temperature range, and has toughness and durability.
very resistant to abrasion and has good mechanical properties at high temperatures.
PEEK (polyether ether ketone): an engineering plastic with high temperature resistance, chemical resistance and fatigue resistance.
resistant to certain chemicals, transparent, and can withstand sterilization for medical purposes.
low-cost, chemically resistant, opaque thermoplastic.
Excellent general-purpose resin, highly resistant to solvents and other chemical substances.
strong, strong and chemical resistant, compared with other thermoplastics, it can withstand repeated sterilization and higher temperatures.
A strong engineering thermoplastic that strikes a balance between physical and chemical properties, making it suitable for high-performance applications.
Lightweight metal with high strength/weight ratio and durable anodizing treatment.
Robust and eye-catching, this metal is ideal for high-pressure and high-temperature applications.
This lightweight, durable material is about 20% lighter than brass and can withstand high pressure and high temperature.
This is the most common O-ring material because it has solvent, oil and water resistance.
Also known as EPR, this material has excellent chemical resistance.
Known for its excellent heat resistance, oxidation resistance, weather resistance and ozone resistance.
Has good temperature resistance. Medical-grade silicones also meet the FDA’s level VI requirements for biocompatibility in life science applications.
Although connectors are sometimes regarded as a secondary component of medical equipment, they should not be blamed on hindsight during the design process. In order to achieve aesthetic goals as well as product performance and patient safety goals, connectors must be considered early in the process. Because the connector is usually the main interface between the user and the device, it plays a key role in the overall design perception. Well-designed connectors make medical equipment easy to use and increase overall satisfaction with the equipment.
Jim Brown is the Medical Marketing Business Unit Manager of CPC (Cold Products Company) in St. Paul, Minnesota. Jim has customized fluid connections for more than 20 years. His expertise includes the application of medical equipment, such as blood pressure monitoring, dialysis and surgical equipment. Jim holds a bachelor’s degree in mechanical engineering from the University of Minnesota Polytechnic Institute. Jim is a member of LifeScience Alley and AAMI, and currently serves as an American expert in ISO technical committee 210/JWG4 to develop standards to prevent misconnection of small-caliber connectors.