DISCLAIMER: “These do not necessarily represent the views of the U.S. Government or Department of Veteran Affairs.“
On the highly limited role of single ventilator / multiple patient workarounds in the COVID-19 epidemic.
The initial logic behind using a single ventilator to support multiple patients is compelling, and speaks to our most basic urge to rescue. There are certain situations in which it would work well – in patients with fundamentally normal lungs, whose compliance can be easily matched and kept matched, who can be deeply neuromuscularly paralyzed, and for whom there is a plan for individualized ventilators to become available soon to make vent weaning/liberation possible. This is exactly the case in well-resourced combat casualty situations, some single-point disasters, and perhaps in an overwhelmed emergency department waiting for the ICU to clean beds.
Unfortunately, these conditions will rarely be met during the COVID-19 epidemic. COVID-19 causes acute respiratory distress syndrome with dynamic changes in compliance from progression of the disease and variation in resuscitation. If patients with unequal compliance are hooked up to the ventilator, then one will be overdistended (causing worsening lung damage) and the other will be underventilated (causing asphyxiation). Our clinical experience has been that compliance can change significantly over 6-18 hours. We know that even transient exposure to large tidal volumes or high plateau pressures can worsen ARDS.
Second, a hallmark of COVID-19 ARDS is marked and disproportionate PEEP responsive, requiring relatively high-levels of PEEP. However, if PEEP is too high, that causes diminished intravascular return, hypotension, and can cause worsening hypoxemia. PEEP levels in the first several patients I saw varied between 10 and 24 on similar FiO2. That variation is easily met individually, but would also require matching and dynamic readjustment in a single ventilator / multiple Patients situation.
The hallmark of effective ventilation is synchronized ventilation allowing sedation reduction and more rapid extubation. Neither is possible for single ventilator / multiple patients situation – which means those ventilators are committed to much longer use in that period, reducing the available pool of ventilators and thereby meaning this strategy offers a substantially less than its initially promised expansion of capacity.
Moreover, the care of COVID19 patient extends beyond the physician doing the initial resuscitation, to a nursing and physical/respiratory therapist team that care for the patient for days to weeks as their hypoxemic respiratory failure and ARDS gradually resolve. The implications of single ventilator / multiple patients for the burden on these other professionals, and their capacity to continue to provide care, need to be determined in advance.
Single ventilator / multiple patients situation will incur therefore multiple harms to patients: likely higher tidal volumes (up to 10% absolute increased mortality risk), lack of daily interruption of sedation (another up to 10% absolute increased mortality risk), prolonged neuromuscular blockade (?50% absolute risk of subsequent disability), unclear but higher rates of iatrogenic shock, high rates of post-extubation post-traumatic stress disorder, and high rates of ventilator-associated pneumonia with grossly inadequate infection control.
As such, it should rarely be used. While comparative effectiveness data are not available, non-invasive ventilation and heated high flow nasal cannula should be widely and maximally used prior to use of Single ventilator / multiple Patients, as their potential harms are much more theoretical, and where estimated, of much lower magnitude.
In general, we know most patients would prefer appropriate palliation to a very high risk of disabling, cognitively impairing, PTSD-exacerbating critical care. (Steinhauser et al JAMA and Ann Int Med 2000). In general, therefore, appropriate palliative care and maximized non-invasive and HHFNC should be preferred.
The Society of Critical Care Medicine (SCCM), American Association for Respiratory Care (AARC), American Society of Anesthesiologists (ASA), Anesthesia Patient Safety Foundation (APSF), American Association of Critical-Care Nurses (AACN), and American College of Chest Physicians (CHEST) issued a consensus statement outlining similar points.
In the event that viable ways to solve the immediate technical problems (e.g. individualized PEEP valves, adjustable pressure limiting valves (APL), volume monitoring) and personnel problems (e.g. nursing and physio/respiratory-therapist protocols and safeguard from emotional distress and infection risk) can be solved, there may be a role for reconsidering this.
But until we can solve these problems, my view is that building tools and protocols for #COVID19 single ventilator / multiple patients is a distraction from more pressing problems like optimizing PPE, expanding nursing + respiratory therapist capacity, and building safer NIV + HHFNC systems. It is unlikely that any health system seriously considering single ventilator / multiple patient scenarios has time for such distractions.
- Farkas J. PulmCrit – Splitting ventilators to provide titrated support to a large group of patients. EMCrit. 25 March 2020. [Accessed 29 March 2020]. Available at URL: https://emcrit.org/pulmcrit/split-ventilators/
- Farkas J. PulmCrit wee – Why the SCCM/AARC/ASA/APSF/AACN/CHEST joint statement on split ventilators is wrong. EMCrit. 29 March 2020. [Accessed 30 March 2020]. Available at URL: https://emcrit.org/pulmcrit/pulmcrit-wee-why-the-sccm-aarc-asa-apsf-aacn-chest-joint-statement-on-split-ventilators-is-wrong/
- Rosenthal BM, Pinkowski J, Goldstein J. ‘The Other Option Is Death’: New York Starts Sharing of Ventilators. The New York Times. [Accessed 29 March 2020]. Available at URL: https://www.nytimes.com/2020/03/26/health/coronavirus-ventilator-sharing.html
- SCCM/ AARC/ ASA/ APSF/AACN/ ACCP Consensus Statement on Multiple Patients Per Ventilator. [Accessed 29 March 2020]. Available at URL: https://www.sccm.org/Disaster/Joint-Statement-on-Multiple-Patients-Per-Ventilato
- Steinhauser KE, Christakis NA, Clipp EC, McNeilly M, McIntyre L, Tulsky JA. Factors Considered Important at the End of Life by Patients, Family, Physicians, and Other Care Providers. JAMA. 2000;284(19):2476–2482. doi:10.1001/jama.284.19.2476
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