A Simulated Single Ventilator / Dual Patient Ventilation Strategy for Acute Respiratory Distress Syndrome During the COVID-19 Pandemic

Jose A. Solis-Lemus; Edward Costar; Denis Doorly; Eric C. Kerrigan; Caroline H. Kennedy; Frances Tait; Steven A Niederer; Peter E. Vincent; Steven E. Williams

Although some cases are asymptomatic, severe disease can cause death at an estimated rate of around 3-4%. 2 Although myocardial damage and circulatory failure contribute to Covid-19 deaths, the main cause of death is respiratory failure 3 and the majority of serious cases require intensive care unit (ICU) admission and mechanical ventilation. It is estimated that the ICU capacity of all EU/EEA countries (including the UK) would be exceeded at a prevalence of 100 hospitalised Covid-19 patients per 100,000 of the population (based on the Hubei providence scenario at the peak of the epidemic). 4 According to the most recent European Centre for Disease Prevention and Control report the majority of EU/EEA countries were predicted to reach this scenario by the end of March 2020. 4 Major difficulties in predicting the course of the outbreak given the exponential spread during the early phase, mitigated by behavioural changes and government methods, mean there is large uncertainty in the models, but widespread agreement that ventilator availability is likely to be a critical factor in patient care. As such, there is worldwide concern that there will be a shortfall of mechanical ventilators at the height of this global pandemic. As one example, estimates of the number of ventilators in the USA range from 60,000 to 160,000, whilst up to 1 million ventilators may be required at the height of the USA pandemic. 5 Regardless of the strategy used for estimating this latter number, the national strategic reserve is not thought to be sufficient to fill the projected gap. 6 Given the predictions for a huge global shortfall in ventilators, strategies have been proposed for ventilator sharing. In 2006, Neyman et al found that a single ventilator could be modified quickly in an emergency department setting to ventilate 4 simulated adult patients for a short period of time. 7 Subsequently Paladino et al successfully ventilated 4 adult-human-sized sheep on a single ventilator for at least 12 hours. 8 During the early stages of the Covid-19 pandemic this approach has received significant media attention, 9 with at least two clinical protocols in development, 10 and it is reported that national decision makers are either considering 11 or have recommended this approach. 12 Importantly, such ventilation strategies assume equal lung physiology in all patients and are likely only to be successful in situations where multiple patients with similar lung physiology require ventilation.