The Repurposed Use of Anesthesia Machines to Ventilate Critically Ill Patients With Coronavirus Disease 2019 (COVID-19)

Maurizio Bottiroli; Angelo Calini; Riccardo Pinciroli; Ariel Mueller; Antonio Siragusa; Carlo Anelli; Richard D. Urman; Ala Nozari; Lorenzo Berra; Michele Mondino; Roberto Fumagalli


BMC Anesthesiol. 2021;21(155) 

In This Article


A major priority amid the emergency response to surges of coronavirus disease-2019 (COVID-19) cases has been to increase hospital capacity, particularly in terms of ICU bed availability.[1] In many hospitals, this undertaking has included converting operating rooms (OR) and post-anesthesia care units (PACU) into temporary ICUs.[1,2]

Using anesthesia machines in addition to standard ICU ventilators significantly increases a hospital's capacity to provide critical ventilatory support. Several authors and societies have advocated using Anesthesia Machines in COVID-19 patients at institutions faced with resource limitations.[3–5]

Critical care ventilators are designed to function as mostly unattended devices. Alarms are usually integrated with an overhead monitoring system and trigger personnel from a distance. Through sophisticated tools and software, different ventilatory modes can be applied in a wide array of critical respiratory conditions. Inspired gases are usually actively humidified, and exhaled breath is dispersed in the room air after filtration with a bacterial filter.[6]

The ventilator apparatus attached to an anesthesia machine is designed to be closely attended by trained professionals in the OR. Anesthesia Machines usually provide ventilation only while the patient is unconscious and paralyzed for surgery, with a limited range of available ventilatory settings and monitoring features. Anesthesia Machine workstations can be used to deliver inhaled anesthetics through dedicated vaporizers. Dry compressed gases are passively humidified through a heat and moisture exchanger, usually with filtration properties. A unique feature of Anesthesia Machines is the ability to regulate an inlet of fresh gas flow, altering the amount of rebreathed exhaled gas via a scavenger system. While the use of filters and a closed system might be attractive options during the pandemic to limit viral contamination of the room and to spare medical gases, long-term use of Anesthesia Machines could also pose several complications.[3,7]

Overall, Anesthesia Machines can provide life-sustaining mechanical ventilation, but they were not originally designed to support critically ill patients for prolonged times.[8] At the start of the 2020 pandemic, a registry was formed to understand patterns and trends in the critical care being delivered to patients with COVID-19 requiring mechanical ventilation. In this retrospective observational study, we investigated how the care of patients who received Anesthesia Machines versus the care of patients who received ICU ventilators impacted mortality. We hypothesized that 60-day survival would be reduced in patients cared for with Anesthesia Machines compared to care that involved standard ICU ventilators.