Patients in healthcare settings often receive medication and medical therapies through a variety of devices or delivery systems. These systems include syringes, catheters, and tubing sets that connect to each other.
Due to the easy-to-use and compatible nature of luers, they are the most frequently used connectors for these systems. Yet, despite their functionality, luers have also contributed to the highest risk of patient injury due to clinicians accidentally connecting to incorrect systems. This causes medication or other fluids to be delivered through improper routes.
To prevent these medical mistakes, having a proper luer design and luer testing is essential to ensure connections remain secure throughout procedures to allow full administration of treatment. This prevents disruption of treatment, risk of contamination, or possible introduction of air.
Importance of Proper Luer Design
Having the proper catheter luer design and adherence to the international standards is essential to ensure expected performance is consistently achieved. The two prevailing standards are ISO 594 testing and ISO 80369 testing. The newer standard, ISO 80369, consisting of eight parts, was introduced in 2011 by the International Organization for Standardization to improve patient safety and reduce the risk of small-bore misconnections used in liquid and gas healthcare applications. ISO 80369-1 defines general requirements. ISO 80369 2-7 defines six different types of luer connections with different designs, so that incompatible connectors can never be accidentally joined together. The standards also define luer tests for compatibility as well as new tests to confirm incompatibility with the other luer designs.
ISO 80369 describes common luer test methods, which are to be completed for all connectors complying to this standard. The purpose of this test protocol is to verify that the design of small-bore connectors meets the functional requirements and non-interconnectability requirements defined in the standard. Many of the test methods in this section are identical to or derived from the previous ISO 594-1 and ISO 594-2.
Improper design or unexpected variability can lead to non-compliance to the standard. At Medical Murray, we test many catheter luers and work with our customers to identify and overcome failures.
Following are the two primary compliance failures we have observed.
Several catheter luer dimensions are captured for the critical features using standard and advanced tools. The impact of out-of-specification dimensions can include the inability to properly attach to mating components, leakage, low separation force to the mating component, and stress cracking. As a result, it is often best to screen components for dimensions as a part of the first article evaluation before initiating the full gamut of ISO 80369 small-bore connector testing.
ISO 80369 provides clear specifications for the dimensional requirements. However, due to the tight tolerances and small component details, they can be difficult to measure and challenging to control in manufacturing. It is our recommendation that catheter luers be evaluated early in the process to confirm adherence to specifications with the use of proper equipment and special fixtures.
Our experience with luer molding and manufacturing luers often with catheter luer over-molding directly onto catheter shafts has led to tight process controls with clearly defined tooling, validation activities, and ongoing lot release testing. Small variations in tooling, the environment (such as humidity), and process parameters can lead to part failure.
A second frequent cause of failure has been related to the material selected for the catheter luer. The material is critical for ensuring proper mating of components, resistance to stress cracking, ensuring adequate separation force, and reducing the risk of leakage. Proper material selection is also critical for biocompatibility compliance and the consistency of manufacturing.
Medical Murray has significant experience with multiple materials in luer connectors, which includes rigid and semi-rigid materials. Some common materials include polycarbonate, nylon, Pebax, PVC, and polypropylene. Selection is dependent on many factors including:
- Durability of material in presence of stresses associated with compatibility to mating components.
- Biocompatability of the material selected.
- Manufacturing considerations to ensure its ability to maintain required tolerances.
- Attachment method to the catheter or tubing. If catheter overmolding is required, the temperature of molding needs to be considered to ensure compatibility. If adhesively bonded, ability for adhesive to securely attach to both materials. If solvent bonded, ability to maintain durability post bonding.
- Ability to effectively sterilize the material, both in terms of ensuring sterility and continued adherence to standards post-sterilization.
Meeting ISO Standards
Medical device and catheter testing for compliance of ISO 80369 is a critical part of the R&D process in preparing a device or delivery system for regulatory submission. Adhering to these standards is essential for not only safety and performance but, most importantly, to avoid potential patient health hazards. The medical device industry must continue to be vigilant when designing devices and delivery systems to ensure that possible misconnection is eliminated.