Episode #309 Mold Risk In Anesthesia Workstations

Opening Clip: There are reports of moisture and mold accumulation in a critical area for anesthesia care, within certain GE HealthCare anesthesia workstations especially when these workstations were used for longer cases and in high humidity clinical settings. We are here to bring you the details of these findings and what the team on the ground discovered during their system-wide investigation including vulnerabilities within ventilator breathing systems. Best of all, we also have well-informed mitigation strategies for moisture management to help keep your equipment clean and dry and your patients safe. This is a Rapid Response to questions from our readers episode that you don’t want to miss.

Hello and welcome back to the Anesthesia Patient Safety Podcast. I’m your host, Alli Bechtel.

Before we dive further into the episode today, we’d like to recognize PPM, Preferred Physicians Medical Risk Retention Group, a major corporate supporter of APSF. PPM has generously provided unrestricted support to further our vision that “no one shall be harmed by anesthesia care”. Thank you, PPM – we wouldn’t be able to do all that we do without you!”

Our featured article is “Moisture, Mold, and More in GE Operating Room Ventilators: System Response and Mitigation” by Sandeep Narayan and Katie Passaretti. This is a Rapid Response Article that was published online February 1, 2026. To follow along with us, head over to APSF.org and click on the Newsletter Heading. The third one down is Rapid Response to Questions from our readers. Then, you can scroll down until you get to our featured article, and I will include a link in the show notes as well.

It all began when two GE HealthCare Aisys CS2 anesthesia workstations in a single facility were found to have black particles on the EZChange module of the Advanced Breathing System and alarm bells went off with concern for mold growth. This facility was part of Advocate Health, a 69-hospital health care system across 6 different states. Check out Figure 1 in the article for a zoomed in picture of the GE ventilator with the circuit removed to reveal the flow sensor unit, the EZChange module, and the CO2 absorber. Figure 2 in the article shows the focus of this investigation, black particle concerning for mold around the valve of the EZChange module where moisture-containing gas leaves the absorbent canister. This EZChange module is a key component since it allows continued ventilation of the patient while changing the CO2 absorbent canister. The black, mold-like particles were seen during close machine inspection after a failed daily checkout and a flow sensor failure alarm event. Following this, an investigation was launched across the health care system.

300 GE HealthCare Operating Room anesthesia workstations were examined. 21 units including Aisys CS2 and Avance CS2 models showed the potential for mold growth. In addition, many additional workstations had significant moisture accumulation within the internal components of the ventilators. Cultures of the black particles were taken from 3 ventilators which grew Cladosporium and alterneria. Another 188 GE HealthCare anesthesia workstations in non-OR areas did not have evidence of moisture accumulation or mold growth. The team reached out to other health care systems and discovered similar reports of mold growth in GE Healthcare workstations.

Next, the team took action with moisture and mold checks every 1-2 weeks to identify any mold regrowth while working with GE Healthcare to determine steps for mold and moisture mitigation.

There was an important question looming…what is the risk to patients if there is concern for mold in the ventilator. There is limited research on ventilator contamination and patient risk. The APSF has reported that the infectious risk from contaminated anesthesia ventilators is low likely due to the caustic nature of CO2 absorbent and effectiveness of breathing circuit filters. There are earlier reports of fungal and bacteria growth in anesthesia breathing circuits, but this was likely due to the reprocessing methods and air drying. It is reassuring that no correlation has been found between organisms in the circuits and postoperative pneumonia and no difference in contamination between high and low fresh gas flow rates.

Further investigation into the anesthesia practices at Advocate Health sites revealed that a new heat and moisture exchange filter was used for each case and replaced during surgery if saturated or visibly contaminated. This filter is a high efficiency viral filter with 99.99% efficiency that is also effective for fungal organisms which are larger than viral particles. The team evaluated 6 months of patient respiratory cultures from 19 different facilities and non-Aspergillus mold species were rarely identified. In addition, there was no association between patients with mold in respiratory cultures and having a recent surgery. The big takeaway here is that the risk to patients is likely minimal. Even with this minimal risk, all of the anesthesia workstations with concern for mold growth were removed from the operating theatres so that sterilization per the manufacturer’s instructions for use.

The next step was to get GE HealthCare involved – they were notified of the findings and provided virtual and in-person support to determine the root causes and mitigation strategies to prevent this from happening in the future. There was also a GE HealthCare support person for each region within the large healthcare system to help address concerns. The root cause was found to be moisture accumulation in the EZChange module so the solutions involved sterilization and moisture mitigation. Moisture in the breathing circuit comes from 2 sources, the patient and the reaction of the absorbent with exhaled CO2. Exhaled gas contains 100% humidity and the absorbent reaction creates heat and water. When the heat and moisture exchange filter is placed at the y-piece, exhaled moisture is absorbed and prevented from entering the breathing circuit. What about the moisture from the absorbent reaction? The amount created depends on the fresh gas flow. When fresh gas flow is less than minute ventilation, the amount of exhaled gas returning to the patient increases leading to more CO2 reacting with the absorbent and creating moisture in the circuit. The investigators determined that even with 2L/min fresh gas flows, there was moisture accumulation in the circuit due to rebreathing. Another consideration is the ambient temperature and colder temperatures cause moisture to condense in the circuit. For anesthesia professionals practicing low-flow anesthesia, moisture mitigation is going to be important.

Here are the details of the case:

• Most end-users lacked awareness that moisture accumulation could be an issue in anesthesia workstations.
• While a few sites within the healthcare system had implemented some moisture mitigation practices, most were unaware of optional moisture mitigation steps that can be employed such as:
  • Add-on condenser for drainage of excess moisture
  • Removal of the breathing circuit overnight
  • Removal of the flow sensor overnight
• Although lower fresh gas flow rates are associated with increased rebreathing, and, therefore, moisture accumulation, mold and moisture were found in ventilators regardless of whether sites routinely practiced low-flow ventilation as part of sustainability efforts.
• Excess moisture accumulation was more common in workstations exposed to higher case volumes and longer surgical durations.
• There are no specific guidelines from manufacturers on sterilization frequency, and facilities lacked a standardized process or adequate training for sterilization.

Based on these findings, here are the practice changes that were implemented in the healthcare system:

1. Extensive anesthesia professional and technician education through grand rounds, emails, and virtual and in-person meetings. Anesthesia professionals were specifically educated on weekly mold and moisture checks and daily moisture mitigation steps, which included removing the breathing circuit and flow sensors overnight. Check out Figures 3 and 4 in the article for an education flyer and mold and moisture check flyer that the team created and used.
2. Flow sensor and advanced breathing system inventory were performed at all practice locations and, where needed, additional components to support moisture mitigation and sterilization were purchased to minimize the risk of interrupting patient care due to moisture and mold.
3. Sites with GE HealthCare anesthesia workstations were instructed on how to inspect for moisture or mold every 1–2 weeks to monitor for regrowth and confirm mitigation effectiveness.
   1. Non-OR areas with shorter case durations, less ventilator utilization, and no initial moisture or mold issues were not required to perform ongoing assessments.
   2. Assessments were discontinued once the individual site had no units with moisture or mold for two audit cycles.
4. Despite routine removal of flow sensors and breathing circuits overnight, higher surgical volume sites continued to identify moisture within the Advanced Breathing System, albeit at a lower frequency.
5. Add-on condenser elements for all OR anesthesia workstations are being purchased from GE HealthCare. This additional step was deemed necessary due to continued moisture accumulation despite a change in practice and the likely increase in complex and longer surgical cases.
6. A multidisciplinary team established an internal procedure and assigned responsibility for monitoring moisture accumulation, assembly/disassembly of ventilators, and sterilization.
7. Annual sterilization of all OR ventilators was also implemented as part of our annual preventative maintenance.
8. GE HealthCare hosted live webinars and developed video-based training for sterile processing and clinical engineering teams on assembly, disassembly, and sterilization of the ventilators.

It was a lot of work to get to this point – discovering that GE HealthCare anesthesia workstations could accumulate moisture leading to mold growth. Without moisture alarms or internal triggers for biologic growth in place, it is difficult to determine internal mold growth in the anesthesia workstations. Another important consideration is that moisture accumulation could impact flow sensors leading to inaccurate tidal volume measurements. The infectious risk to patients is likely minimal with the use of Heat and Moisture Exchange Filters between the patient and the ventilator, but this risk depends on local practices.

The answer is not just –increase fresh gas flows to decrease rebreathing since this would waste anaesthetic gases which has a negative environmental impact and increased cost. We have talked about low flow anesthesia before on this podcast and this is a safe and effective practice when moisture mitigation practices are used. Another consideration is that anesthesia workstation sterilization is a complex undertaking that requires disassembly and reassembly of the advanced breathing system, so the focus must be on moisture mitigation to prevent mold growth rather than frequent sterilization.

The investigators have some questions for GE Healthcare. Here they are?

1. While newer models of GE anesthesia workstations are designed with a built-in condenser, GE HealthCare designates the condenser as an optional product for older models. We have continued to see mold growth despite implementing two moisture mitigation solutions that included removing the flow sensor and circuits overnight. Based on our experience that moisture accumulated despite daily moisture mitigation practices, we believe the condenser is a necessary moisture mitigation solution for all compatible older models and not an optional product.
2. During discussions with other health systems using GE workstations, some sites reported implementing all moisture mitigation solutions while others were not aware of moisture mitigation solutions and their importance. Could GE HealthCare share what initiatives have been undertaken or are being planned to ensure a comprehensive and consistent moisture mitigation education for all clinical sites in the country?

Here are some questions that the investigators have for the APSF:

1. Please educate on the need for multiple filter use for each patient. Is it necessary to have both HMEF and expiratory filters for all patients? If a site decides to use just one filter, which filter is the preferred filter for adult and pediatric populations?
2. Please educate on the need for moisture mitigation when using non-GE HealthCare ventilator brands.
3. Is there any evidence or guidance on moisture levels that are safe within ventilators and breathing circuits?
4. Please provide guidance on OR ventilator sterilization frequency. Should this be a part of yearly preventative maintenance?

We have reached the end of the investigation and we may be ending the show today with lots of questions, but we’ll be back next week with expert answers. Have you noticed any moisture accumulation in the breathing circuits in your Ors? What about any possible mold growth? Make sure you tune in next week for the rapid responses to these questions.

If you have any questions or comments from today’s show, please email us at [email protected]. Please keep in mind that the information in this show is provided for informational purposes only and does not constitute medical or legal advice. We hope that you will visit APSF.org for detailed information and check out the show notes for links to all the topics we discussed today.

As we wrap up this episode of the Anesthesia Patient Safety Podcast, we’d love to hear from you. If you’ve encountered a technology-related safety concern in your practice, consider submitting a Rapid Response article to the APSF Newsletter. The goal of the Rapid Response column is to encourage timely communication about emerging safety issues, while also providing input and perspective from manufacturers and industry representatives. Submissions should be limited to 1,000 words and up to 15 references. Your experience could help improve patient safety for anesthesia professionals around the world.

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Until next time, stay vigilant and stay informed so that no one shall be harmed by anesthesia care.

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