The COVID-19 pandemic in New York City during spring 2020 resulted in an unprecedented number of patients requiring mechanical ventilation. With the need for intensive care unit (ICU) beds and ventilators exceeding supply, anesthesia machines were used as ventilators in non-OR locations, an off-label use.1 The APSF/ASA document “Guidance on Purposing Anesthesia Machines as ICU Ventilators” includes “Key Points to Consider in Preparing to Use Anesthesia Machines as ICU Ventilators,” which notes that any location with high pressure air and oxygen might be acceptable.2
We report the case of an anesthesia machine ventilator failure in a COVID-19 patient who was being managed in a windowless negative pressure room in a telemetry unit that had been converted to a temporary COVID-19 ICU. This case highlights that novel use of standard equipment is subject to unforeseen problems.
Report of the Case
A 66-year-old man with a history of noninsulin-dependent diabetes was admitted to a temporary COVID-19 ICU for acute respiratory failure requiring tracheal intubation and mechanical ventilation. Temporary negative pressure rooms had been created by replacing the exterior window of each room with a hardboard panel that contained a cutout for a HEPA filter/extractor fan exhaust duct (Air Shield 550 HEPA Air Scrubber, AER Industries, Irwindale, CA). Anesthesia workstations (Aisys Carestation CS2, GE Healthcare, Waukesha, WI) were being used as ventilators in this temporary ICU, managed 24/7 by a group of anesthesiologists. The rooms had no interior or door windows, but indirect viewing was provided via a remote visual patient monitoring system (AvaSys Telesitter, Belmont, MI). Monitoring was via a central station telemetry network (GE CARESCAPE, GE Healthcare, Waukesha, WI) to which the workstation physiologic monitor had been connected, with high volume audio alarms for abnormal rhythms and bradycardia/tachycardia, and the default low volume audio alarm for low SpO2.
On hospital day 10, an audible alarm sounded at the central station and the SpO2 was noted to be 45%. The care team donned PPE, entered the patient’s room and observed that mechanical ventilation had ceased, the extractor fan was off, and the room was very warm. The Aisys control screen was dark, the AC power indicator light was off, but the physiologic monitor was on and functioning. The patient was immediately disconnected from the breathing circuit, ventilated using a self-inflating manual ventilation bag, and the SpO2 rapidly returned to baseline levels. It was noted that the bed (HillRom Progressa Pulmonary, HillRom, Chicago, IL) was plugged into an auxiliary outlet on the extractor fan, the fan was plugged into a floor level electrical outlet, and the Aisys workstation was plugged into a separate floor-level outlet. The workstation was immediately connected to a different electrical outlet, the AC power indicator light came on, and the workstation rebooted. After a pre-use checkout had been performed, the patient was reconnected to the breathing circuit and mechanical ventilation resumed normally.
The Aisys workstation was subsequently removed from the room for interrogation and replaced with a new one. Hospital engineering staff found that a circuit breaker for the room had tripped and it was reset. No problem was found with the extractor fan and it was restarted.
Root cause analysis
The workstation’s failure was caused by interruption of its power supply due to a tripped circuit breaker. Review of the service log revealed an AC power loss, appropriate cutover to the backup battery, and eventual complete discharge of the battery. Several alarm messages had been displayed on the workstation screen beginning 28 minutes after the AC power loss progressing from “Battery Low”, “Battery V Low” to “Battery V VERY LOW” and, after 1 hour 43 minutes, to “Battery Empty.” The system shut down after 1 hour 52 minutes. The service log verified that the system operated as intended,3 but these alarm messages were not visible to the staff outside the patient’s room.
This case illustrates some of the problems that could be encountered during the COVID-19 pandemic, namely creating a makeshift ICU on short notice and using an anesthesia workstation to ventilate a critically ill patient in a closed room, with less-than-ideal remote monitoring. During normal use of an anesthesia workstation, a qualified anesthesia provider is in constant attendance, able to view the screens, hear audible alarms, and make adjustments as necessary. The backup battery on the Aisys workstation is specified to last from 50-90 minutes depending on the model, but in this case it lasted almost two hours. In contrast, an ICU ventilator such as the Puritan Bennett 980 (Medtronic, Boulder, CO) is specified to have a one-hour backup battery.4 While ventilator failure in this case was caused by loss of external electrical power, failure of a ventilator’s internal power supply has also been reported.5 Fortunately the physiologic monitor (Carescape b650, GE Healthcare, Waukesha, WI) had its own backup battery with a 1-2 hour run time,6 and was connected to the telemetry network, thus alerting staff.
The cause of the tripped circuit breaker is unknown. The electrical power supply to the room comprised two dedicated 15A circuits with white outlets, two 20A circuits that were shared with the adjacent room and also had white outlets, and one 20A emergency circuit with red outlets. The white electrical outlets had no markings to indicate to which of the circuits they were connected.
It is unlikely that a device in the adjacent room caused the circuit breaker to trip because that room did not lose power. The most likely explanation is that the bed, extractor fan, telemedicine monitor and anesthesia workstation were all connected to the same 15A circuit, and the total current draw from all devices exceeded 15A. The extractor fan draws 2.5A, and the bed can draw up to 12A, leaving a very small margin before the circuit would be overloaded. Notably, in many hospitals (including ours) the circuit breaker panels are locked and can only be accessed by engineering due to security concerns. Limited accessibility can cause a delay in reinstating power.7,8
The APSF/ASA Guidance includes the recommendation that “An anesthesia professional needs to be immediately available for consultation, and to ‘round’ on these anesthesia machines at least every hour.” During the height of the pandemic, with limited PPE, limited staff, 168 ventilated patients and 18 patients being ventilated using anesthesia workstations, hourly rounding was simply not possible. The same problem could also have occurred with a standard ICU ventilator, since they also have limited backup power, and aside from some very new models, lack remote monitoring capability. One solution not available to us at the time is to detach the control and monitoring screens from the Aisys workstation and, using special extension cables, move them to outside the room thereby allowing control of gas flows and ventilation as well as remote monitoring.9
In conclusion, the use of an anesthesia workstation as an ICU ventilator is feasible in a crisis situation, but increased vigilance is required to recognize and manage unanticipated problems.
- Haina KMK Jr. Use of Anesthesia Machines in a Critical Care Setting During the Coronavirus Disease 2019 Pandemic. A A Pract. 2020;14(7)
- APSF/ASA Guidance on Purposing Anesthesia Machines as ICU Ventilators.
- GE AISYS CS2 USER’S REFERENCE MANUAL. Accessed August10, 2020.
- Technical Specifications for U.S. Puritan BennettTM 980 Ventilator System. Medtronic/Covidien; 2016.
- Davis AR, Kleinman B, Jellish WS. Cause of Ventilator Failure is Unclear – Anesthesia Patient Safety Foundation.
- GE Healthcare. CARESCAPE Monitor B650.; 10/2010.
- Carpenter T, Robinson ST. Response to a Partial Power Failure in the Operating Room. Anesthesia & Analgesia. 2010;110(6):1644.
- August DA. Locked out of a box and a process. Anesth Analg. 2011;112(5):1248-1249; author reply 1249.
- Connor CW, Palmer LJ, Pentakota S. Remote Control and Monitoring of GE Aisys Anesthesia Machines Repurposed as Intensive Care Unit Ventilators. Anesthesiology. 2020;133(2):477-479.