Catalog of Regulatory Science Tools to Help Assess New Medical Devices
This regulatory science tool presents a lab method that may be used for used for measuring aerosol emission from water-based heater cooler devices (HCDs). Please see appendix.
Technical Description
Aerosols inadvertently generated from contaminated water in HCDs have been associated with multiple infections[1]. The FDA requests medical device manufacturers to provide performance data that demonstrates that the risks of aerosol emission from their heater cooler devices are low. This in vitro tool describes how to prepare samples of clinically relevant test organisms before performing aerosolization testing with HCDs and how to then sample these organisms post-aerosolization. This tool also provides protocols for a positive control that can be used for validating the sampling methodology before testing HCDs.
Intended Purpose
Heater Cooler devices (HCDs) are used in patients who undergo cardiopulmonary bypass surgeries. The current technical protocols may assist medical device manufacturers or third-party testing facilities with testing aerosol emission from HCDs.
Related product codes: DWC or DWJ
Testing
Bubbling in contaminated water tanks is believed to be the primary mode of aerosol generation in heater cooler devices. The article by Guha et al[2] describes how a bubbler (a small, handheld pipe that uses water to filter smoke) can be used as a positive control for device manufacturers. The bubbling characteristics were qualitatively matched with bubbling observed in heater cooler devices. The publication also demonstrates how one biological assay can be used for collection and quantifying aerosol emissions in heater coolers. Inter-species variability, repeatability, and operator to operator variability were also characterized.
Limitations
This tool is not designed to be part of a physical assay to quantify and analyze total aerosol emission from heater cooler devices.
This assay cannot quantitatively determine the size distribution of bioaerosols.
Supporting Documentation
The basis for this tool can be found in the publication:
- Guha, S., Wolloscheck, D., Abdali, N., Wentz, C., Gillette, N., Bauer, K. A., & Weeks, J. W. (2022). A methodology for investigating aerosolization of nontuberculous mycobacteria from contaminated heater cooler devices. Frontiers. https://doi.org/10.3389/frwa.2022.902872
Given the complexities of working with Non-tuberculous Mycobacterium (NTM) aerosols, we recommend that the user be proficient in growth and isolation of NTM. We also recommend that testing be conducted in a BSL 2 laboratory with adequate safety controls to protect the experimenter from aerosol exposure (for example: experiments performed within a 6’ Class II Type A2 or other Biosafety Cabinet).
We recommend the use of the following testing parameters:[1]
Testing Parameters
- Test organism selection:
- Mycobacterium chimaera has been associated with patient infections during heater cooler use. Therefore, device manufacturers should use this organism for their studies.
- Positive control criteria:
- Positive control should be capable of generating reasonable concentration of M. chimaera aerosols with a low air flow rate of (0.2 Liters/minute) and with a liquid inoculum containing M. chimaera at a concentration of (105 CFU/milliliters).
Tool Output
If the test results indicate that the positive control generates sufficient M. chimaera aerosols, then the biological assay used in the positive control may subsequently be employed for quantifying the extent of aerosol emission from the heater cooler device.
A protocol for preparing NTM solution, measuring concentrations, description of a positive control and an assay is provided as an attachment.
Additional resources for informational use only
The following publication discusses additional considerations for testing in heater coolers and similar reprocessed devices:
- Weeks, J.W., Segars K., & Guha S. (2020) The Research Gap in Non-tuberculous Mycobacterium (NTM) and Reusable Medical Devices. Frontiers in Public Health. https://doi.org/10.3389/fpubh.2020.00399
Contact
Tool Reference
- In addition to citing relevant publications please reference the use of this tool using RST24CV04.01