Authors: Narayan S et al.
Anesthesia Patient Safety Foundation Newsletter, volume 41, number 1, February 2026.
Summary
This article describes a system-wide response to reports of moisture accumulation and mold-like debris within certain GE HealthCare anesthesia workstations, focusing on patient safety risk assessment, root-cause analysis, mitigation strategies, and lessons for perioperative teams. The report originates from a large multistate health system that identified black particles consistent with mold on components of the Advanced Breathing System, initially detected after a failed daily checkout and a flow sensor failure alarm. A multidisciplinary group including anesthesia, infection prevention, technicians, administration, and clinical engineering investigated the scope of the issue.
System inspection of operating room anesthesia workstations identified a subset of units with suspected mold and additional units with significant internal moisture accumulation. Cultures from several devices grew environmental molds, prompting immediate risk assessment and removal of affected machines from service for sterilization per manufacturer instructions. Peer outreach identified similar experiences in other health systems, including reports of recurrence shortly after reprocessing, supporting the need for ongoing surveillance and consistent mitigation practices.
The authors review available evidence suggesting that infectious risk to patients from contaminated anesthesia ventilators is generally low, especially when high-efficiency filters are used between the patient and ventilator components. In their system, routine use of a new heat and moisture exchange filter with each case, with replacement if saturated or visibly contaminated, was a key protective practice. Review of respiratory culture data across multiple sites found mold species rarely, with no clear association to recent operative procedures. While infectious risk was deemed minimal, the report emphasizes that moisture and biologic material can still create patient safety concerns through equipment malfunction, including flow sensor issues that may impair tidal volume measurement accuracy.
A major contribution of the article is its practical explanation of why moisture accumulates in anesthesia workstations. Moisture originates from fully humidified exhaled gases and from water production during carbon dioxide absorption. Moisture retention is influenced by rebreathing, fresh gas flow, ambient temperature, and case duration. Even at moderate fresh gas flows, enough rebreathing may occur to allow moisture buildup, especially with high case volume and long cases. The authors stress that simply increasing fresh gas flow to eliminate rebreathing is not an acceptable solution because it increases anesthetic gas waste, expense, and environmental impact, undermining low-flow sustainability goals.
The investigation identified a lack of user awareness and inconsistent implementation of manufacturer-described moisture mitigation steps. Many sites were unaware of optional measures such as add-on condensers, removing breathing circuits overnight, and removing flow sensors overnight. There were also gaps in standardized sterilization frequency and training for assembly, disassembly, and reprocessing of the breathing system.
In response, the health system implemented education, routine mold and moisture checks, standardized overnight moisture mitigation practices, expanded inventory of components to support reprocessing without disrupting clinical operations, and defined multidisciplinary responsibilities for monitoring and sterilization workflows. Persistent moisture at higher-volume sites led to the decision to purchase add-on condenser elements for compatible older models. Annual sterilization of operating room ventilators was incorporated into preventive maintenance, and additional training resources were developed in collaboration with the manufacturer.
The article concludes that moisture accumulation in anesthesia workstations can occur without visible external signs or automated alerts, and that routine surveillance and mitigation strategies are necessary where risk exists. It emphasizes balancing low-flow anesthesia goals with moisture management, strengthening education and standardization for reprocessing, and clarifying guidance on filtration strategies, moisture thresholds, and sterilization frequency. The report also raises practical questions for both the manufacturer and APSF regarding consistent education, required filtration configurations, and evidence-based standards for safe moisture levels and maintenance intervals.
Key Points
Moisture accumulation and mold-like debris were identified in a subset of GE HealthCare OR anesthesia workstations during system-wide evaluation
Infectious risk to patients was assessed as minimal where high-efficiency filters were routinely used, but equipment integrity and measurement accuracy remain concerns
Moisture originates from humidified exhaled gas and CO2 absorber reaction, and is influenced by rebreathing, temperature, case duration, and workload
Many end-users were unaware of moisture mitigation options and lacked standardized sterilization and inspection processes
Mitigation strategies included routine surveillance checks, overnight removal of circuits and flow sensors, increased spare-part inventory, and standardized sterilization workflows
High-volume sites may require add-on condensers for older compatible models to reduce persistent moisture
Increasing fresh gas flow to eliminate rebreathing is not a preferred solution due to waste, cost, and environmental impact
Thank you to the Anesthesia Patient Safety Foundation for allowing us to summarize and share this APSF Newsletter article addressing anesthesia workstation moisture, mold mitigation, and patient safety.