clinical NEWS

JULY 20, 2O22

Using Filters To Reduce Infections Associated with Heater-Cooler Units

The US-FDA has issued a notice1 last month regarding the need for new strategies in preventing infections from the use of heater-cooler units (HCUs). Over the last few years, there have been reports on the association of nontuberculous mycobacteria (NTM) infection and the use of HCUs on patients undergoing cardiothoracic surgery.

The FDA have identified the following as potential causes for the contamination.
1)    Aerosolization. Water tanks are not airtight so bacteria that grew inside can escape through air bubbles.

CP4000H + 冷温水槽用除菌フィルター SHIELD

2)    Laminar flow disruption. The distance and direction of the heater-cooler’s exhaust fan can disrupt the laminar flow inside the operating room. Air flow can carry the aerosolized bacteria into the surgical field.
3)    Heater-cooler design. Water filters (0.22 micron) should be able to remove most NTM from the tap water used in heater-cooler devices.

Following this guidance, Technowood conducted testing to confirm whether the addition of the SHIELD filter (0.2 micron) will be able remove bacteria from the water circulating inside the CP4000H Compact Heater-Cooler.

With the filter and roller pumps attached, the unit was operated at 37oC simulating clinical use. Water samples were then collected at 1, 5 and 10 minute intervals and used for a 7-day bacterial culture test. Bioburden testing confirmed that bacterial growth can be seen on the water inlet. However, through filter use, the number of bacteria in the outlet decreased to single digits in 10 minutes.  

HCUs are also used in extracorporeal membrane oxygenation (ECMO). ECMO usage has expanded significantly over the last couple of years due to COVID-19. Unlike in cardiothoracic surgery where HCUs are used for hours, ECMO use can last weeks or even months. For this reason, filter function needed to be validated after prolonged use. After 21 days of continuous HCU and filter use, the micron rating of the SHIELD filter was tested. The used filter was able to capture 0.3 μm particles showing the same filtration efficiency as a new filter.

Furthermore, since the filter makes use of polysulfone fiber membrane, there was little change in the water flow rate to the heat-exchanger in both short-term and long-term use.

Using SHIELD filter on the CP4000H Compact Heater-Cooler can mitigate potential cardiac surgery infections risk without compromising HCU performance.

1. Center for Devices and Radiological Health. (2022, June 14). FDA's Ongoing Evaluation and Continued Monitoring of Reports of Nontuberculous Mycobacteria Infections Associated with Water-Based Heater-Cooler Devices. U.S. Food and Drug Administration.


Related device

CP4000H Compact Heater-Cooler with SHIELD filter

With its compact design, the CP4000H can be used for cardiac bypass surgery and extracorporeal membrane oxygenation (ECMO). Operability and visibility has been improved through the upgraded detachable LCD touch panel. The unit can be equipped with the Shield filter to reduce bacterial contamination and to lessen the risk of patient infection during cardiothoracic surgeries.


Not all products shown are approved for sale in all countries.
Please contact the regional Technowood representative for more information.

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