Author: Michael Vlessides
One of the most worrisome aspects of the COVID-19 pandemic is an impending large-scale shortage of mechanical ventilators. Yet as a team of industrious physician anesthesiologists has learned, anesthesia machines can be safely repurposed for use as ICU ventilators, greatly increasing the nation’s ability to treat patients who become critically ill with the disease.
Given this potential, these clinicians urged their colleagues to begin work on idle anesthesia machines in preparation for a possible flood of patients who will require ventilation. Their call to action was supplemented by a joint guidance document from the American Society of Anesthesiologists (ASA) and the Anesthesia Patient Safety Foundation (APSF) (www.asahq.org/in-the-spotlight/coronavirus-covid-19-information/purposing-anesthesia-machines-for-ventilators).
“There is quite a bit of concern now that we’re going to run out of traditional ICU ventilators,” said Jeffrey M. Feldman, MD, MSE, a professor of clinical anesthesiology and critical care at the University of Pennsylvania and a member of the ASA’s Committee on Equipment and Facilities. “One of the reasons we’re focusing our energy on the anesthesia machines is that they’re the most readily available source of alternative ventilators in most institutions.”
This effort is aided by the fact that elective procedures have been cancelled at most hospitals. “These machines are sitting there and readily available,” Dr. Feldman said.
The document, “APSF/ASA Guidance on Purposing Anesthesia Machines as ICU Ventilators,” is now available on each organization’s website and includes two elements: a detailed how-to guide plus a two-sided reference guide.
The detailed guide covers many topics on repurposing anesthesia machines as ICU ventilators. Most of the document focuses on equipment considerations, including:
- machine setup;
- self-test management;
- desired inspired oxygen concentration delivery;
- total fresh gas flow settings;
- strategies for conserving oxygen;
- humidification considerations;
- ventilation monitoring; and
- processing between patients.
The bedside guide summarizes the guidance. “But more importantly,” Dr. Feldman said, “it provides a checklist of the things that need to be done to monitor the machines at different time intervals, to see how well they’re functioning.”
Once an anesthesia machine has been repurposed into an ICU ventilator, hospitals will need to decide where these machines will be put into service. Idle ORs are a potential option, but as Dr. Feldman said, far from perfect. “The problem is you have to reproduce critical care treatment in an operating room, with all the facilities and resources that requires,” he noted. “It’s also not a very efficient space, unless you find a way to fit multiple patients into each OR. But you’re probably only going to have enough resources to get two anesthesia machines in one room.”
A Job for Anesthesiologists
The next issue is ongoing management of the devices and the patients they serve. As Dr. Feldman explained, anesthesiologists are in a unique position to assume these roles.
“In general, respiratory therapists and intensivists who are comfortable with ICU ventilators almost certainly won’t be aware of the features of an anesthesia machine,” he said. ‘So, we’re recommending that anesthesiologists be immediately available to manage the anesthesia machines and assist their critical care colleagues in the care of these people. It’s a great opportunity for anesthesia professionals to contribute to caring for patients during this crisis and a way to bring our specialty skills to bear.”
For clinicians who may not feel comfortable assuming this role, the ASA is also collaborating with the Society for Critical Care Medicine (SCCM) to make a host of educational materials available on its website, at www.sccm.org/Disaster.
The use of an anesthesia machine as an ICU ventilator is still considered an off-label use, but the FDA released a letter to health care providers on March 22, allowing this usage.
In its letter, the agency stated that “anesthesia gas machines capable of providing controlled ventilation or assisted ventilation may be used outside of the traditional use for anesthetic indication. Because of significant differences between the anesthesia gas machine and traditional critical care ventilators, use or supervision by an anesthesia provider is recommended.”
Properly maintained and managed, anesthesia machines offer one notable benefit over existing ICU ventilators: They use oxygen much more efficiently. As Dr. Feldman explained, however, this depends on whether the anesthesia machine has a bellows-type or mechanical ventilator.
“Mechanical ventilators don’t use any oxygen to run the ventilator, just the oxygen needed for the patient,” he said. “Bellows ventilators are pneumatic and are typically configured to use 100% oxygen to drive the ventilator. So, in addition to the oxygen needed for the patient, they consume compressed oxygen to drive the ventilator.
“Nevertheless, [General Electric] has a fix on their bellows ventilators that allows you to convert them from using 100% oxygen to compressed air,” Dr. Feldman noted. The ASA/APSF guidance also includes detailed instructions on how to accomplish this.
“It’s something that can be done in a hospital by a clinical engineer,” he added.
Ventilators Not for Sharing
Another benefit of such repurposing is it will likely stop ventilator sharing, which the ASA has warned against, saying it may actually put patients at increased risk instead of helping them. First raised by New York’s Gov. Andrew Cuomo as a possible solution to looming shortages, ventilator sharing is dangerous because ventilation needs to be individually tailored and continuously monitored, an impossibility when machines are shared. Nonetheless, New York state hospitals are currently allowed to employ this strategy.
Although Dr. Feldman acknowledged that some practitioners may have concerns about repurposing anesthesia machines, he noted that it poses no risk when proper management and maintenance take place. “There are some concerns that anesthesiologists need to be aware of, which is why we’ve added a monitoring schedule to the quick reference guide,” he said.
“For example, the accumulation of water in the anesthesia machine can pose a problem if it’s not identified. That’s why we included hourly checks for things like humidity filters and breathing circuits, to make sure they don’t become a problem.”
Will this potential influx of tens of thousands of ventilators be enough? Time will tell. For his part, Dr. Feldman is hopeful that repurposing anesthesia machines will at least provide a short-term fix while ventilator manufacturers scramble to come up with alternatives.
“I’m really grateful for the efforts everyone has put into making this happen so quickly in the face of the virus,” he concluded. “This is a daunting challenge, but I think we’re up for it.”