Catalog of Regulatory Science Tools to Help Assess New Medical Devices
This regulatory science tool presents a lab method for enteral tubes gravity flow rate testing and selection criteria for the test fluid. Please see appendix.
Technical Description
Fluid Properties
The tool recommends use of either a glycerin/water mixture with viscosity ≥ 10 centipoise or with non-Newtonian shear thinning clinical diets that exhibit viscosity of > 10 centipoise at clinically relevant rates of 100 s-1 at room temperature. Further details are provided in supporting documentation section.
Flow Rate Testing
For gravity flow rate testing, manufacturers can follow the procedures recommended in FDA-recognized standards ASTM F2528-6 or ISO 20695, or they can refer to the supporting documentation below. The supporting documentation complements the standards and provides additional details on how to perform the testing.
Note: This tool was previously listed in the Catalog of Regulatory Science Tools to Help Assess New Medical Devices as “Use of Newtonian Analog Fluids and 3D Printing to Evaluate Flow Rates of Diets in G-Tubes.”
Intended Purpose
The tool provides flow-rate-testing protocols for two scenarios – one in which the manufacturer already has a finished enteral tube, and another in which the manufacturer is currently optimizing their enteral tube design.
The tool can be used to obtain flow rates (in mL/s) for both a predicate device and a subject device. If the flow rate in subject device using the proposed fluids is found to be significantly lower than the predicate device, then it is likely that patients will see a lower delivery rate of nutrition, relative to the predicate device when using the subject device.
Regulatory Evaluation
This tool is intended to compare the gravity-flow-rate performance of the subject device with predicate. It can also be used by device manufacturers currently developing enteral tubes, to optimize the connector section of the enteral tube design. This tool does not replace other special controls or other design requirements discussed in FDA-recognized standards ASTM F2528-6, ISO 80369-3 and ISO 20695.
Regulatory Background and Intended Population
The test protocol applies to enteral tubes with product codes PIF and KNT. Such devices are typically placed percutaneously and connected to the stomach through an established gastrointestinal stoma tract. These devices are used for enteral feeding, medication administration, or decompression for both adult and pediatric patients.
Testing
This tool offers three different test protocols for device manufacturers and developers who:
- want to choose a fluid for gravity flow testing for their predicate and subject G-tubes should refer to protocol P1 listed in the attachment.
- are planning to use their finished G-tubes for flow-rate testing can either refer to FDA-recognized standards ASTM F2528-6, or ISO 20695, or can alternatively refer to protocol P2 listed in the attachment.
- do not have a finished G-tube, who are developing new G-tubes using the FDA-recognized ISO 80369-3:2016 standard and would like to perform testing to optimize their G-tube design should refer to protocol P3 listed in the attachment.
Given the simple nature of the tests and sample preparation, proficiency in wet lab is not required.
Limitations
This tool is based upon research conducted by the FDA in response to observations that tests involving gravity-driven flows of water in enteral tubes do not accurately simulate real-world conditions.
This tool should not be used with enteral fluids that are not well blended, as the particulates may clog the enteral tubes and influence flow rate testing results.
Supporting Documentation
Detailed Methodology
See instructions in Appendix below.
References used for this tool
- The following publication demonstrated that gravity-flow-rate testing with water is not worst case and that testing should be performed with nutritional diets:
Guha S., Ravi N., Silverstein J.S., Cooper J.C., Myers M.R., In vitro Performance Testing of Legacy and ENFit Gastrostomy Tube Devices Under Gravity Flow ConditionsExternal Link Disclaimer. Journal of Parenteral and Enteral Nutrition. 2018, 42(8): 1334-1341. - The following publication demonstrated that glycerin-water mixtures can act as useful surrogates for nutritional diets in gravity-flow-rate testing. It also provides methodology for flowrate testing during the development phase of an Enteral tube, performed to optimize the connector section and minimize reduction in flow rates through devices:
Guha S., Herman A., Herbertson L., Antonino M.J., Silverstein J.S, Cooper J., Myers M.R., Technical Considerations for medical device manufacturers when designing gastrostomy tubes (G-tubes) using the new ISO 80369-3 connectorExternal Link Disclaimer. Plos One. 2020, 15(7), e0236644.
Additional resources for informational use only
Gravity flow testing with blenderized diets
Guha, S., Bouhrira, N., Antonino, M.J., Silverstein, J.S., Cooper, J., Myers, M.R., Impact of Design Changes in Gastrostomy tube (G-tube) devices for patients who rely on home-based blenderized diets for enteral nutrition. Journal of American College of NutritionExternal Link Disclaimer. 2019, 38(4): 311-317. Link:
Invited review of current literature on ISO 80369-3 based Gastrostomy tubes and their performance
Guha, S., Herman, A., Antonino, M.J., Silverstein, J.S., Venkataraman-Rao, P., Myers, M.R., Synthesis of research on ENFit gastrostomy tubes with potential implications for US patients using these devicesExternal Link Disclaimer. Nutrition in Clinical Practice. 2022.
Contact
Tool Reference
- In addition to citing relevant publications please reference the use of this tool using RST24CV07.01