Review of Anesthesia Versus Intensive Care Unit Ventilators and Ventilatory Strategies: COVID-19 Patient Management Implications.

The coronavirus disease 2019 (COVID-19) respiratory illness has increased the amount of people needing airway rescue and the support of mechanical ventilators. In doing so, the pandemic has increased the demand of healthcare professionals to manage these critically ill individuals. Certified Registered Nurse Anesthetists (CRNAs), who are trained experts in airway management and mechanical ventilation with experience in intensive care units (ICUs), rise to this challenge. However, many CRNAs may be unfamiliar with advancements in critical care ventilators. The purpose of this review is to provide a resource for CRNAs returning to the ICU to manage patients requiring invasive mechanical ventilation. The most common ventilator modes found in anesthesia machine ventilators and ICU ventilators are reviewed, as are the lung-protective ventilation strategies, including positive end-expiratory pressure, used to manage patients with COVID-19-induced acute respiratory distress syndrome. Adjuncts to mechanical ventilation, recruitment maneuvers, prone positioning, and extracorporeal membrane oxygenation are also reviewed. More research is needed concerning the management of COVID-19-infected patients, and CRNAs must become familiar with their ICU units' individual ventilator machine, but this brief review provides a good place to start for those returning to the ICU.

Multiplex Ventilation: A Simulation-Based Study of Ventilating 2 Patients With a Single Ventilator.

BACKGROUND: The overwhelming demand for mechanical ventilators due to COVID-19 has stimulated interest in using one ventilator for multiple patients (ie, multiplex ventilation). Despite a plethora of information on the internet, there is little supporting evidence and no human studies. The risk of multiplex ventilation is that ventilation and PEEP effects are largely uncontrollable and depend on the difference between patients' resistance and compliance. It is not clear whether volume control ventilation or pressure control ventilation is safer or more effective. We designed a simulation-based study to allow complete control over the relevant variables to determine the effects of various degrees of resistance-compliance imbalance on tidal volume (VT), end-expiratory lung volume (EELV), and imputed pH. METHODS: Two separate breathing simulators were ventilated with a ventilator using pressure control and volume control ventilation modes. Evidence-based lung models simulated a range of differences in resistance and compliance (6 pairs of simulated patients). Differences in VT, EELV, and imputed pH were recorded. RESULTS: Depending on differences in resistance and compliance, differences in VT ranged from 1% (with equal resistance and compliance) to 79%. Differences in EELV ranged from 2% to 109%, whereas differences in pH ranged from 0% to 5%. Failure due to excessive VT (ie, > 8 mL/kg) did not occur, but failure due to excessive EELV difference (ie, > 10%) was evident in 50% of patient pairs. There was no difference in failure rate between volume control and pressure control ventilation modes. CONCLUSIONS: These experiments confirmed the potential for markedly different ventilation and oxygenation for patients with uneven respiratory system impedances during multiplex ventilation. Three critical problems must be solved to minimize risk: (1) partitioning of inspiratory flow from the ventilator individually between the 2 patients, (2) measurement of VT delivered to each patient, and (3) provision for individual PEEP. We provide suggestions for solving these problems.