Increasing ventilator surge capacity in disasters: Ventilation of four adult-human-sized sheep on a single ventilator with a modified circuit

doi:10.1016/j.resuscitation.2007.10.016

Resuscitation

Volume 77, Issue 1, April 2008, Pages 121-126

https://doi.org/10.1016/j.resuscitation.2007.10.016 Get rights and content

Summary

Objective

Recent manmade and natural disasters have focused attention on the need to provide care to large groups of patients. Clinicians, ethicists, and public health officials have been particularly concerned about mechanical ventilator surge capacity and have suggested stockpiling ventilators, rationing, and providing manual ventilation. These possible solutions are complex and variously limited by legal, monetary, physical, and human capital restraints. We conducted a study to determine if a single mechanical ventilator can adequately ventilate four adult-human-sized sheep for 12 h.

Methods

We utilized a four-limbed ventilator circuit connected in parallel. Four 70-kg sheep were intubated, sedated, administered neuromuscular blockade and placed on a single ventilator for 12 h. The initial ventilator settings were: synchronized intermittent mandatory ventilation with 100% oxygen at 16 breaths/min and tidal volume of 6 ml/kg combined sheep weight. Arterial blood gas, heart rate, and mean arterial pressure measurements were obtained from all four sheep at time zero and at pre-determined times over the course of 12 h.

Results

The ventilator and modified circuit successfully oxygenated and ventilated the four sheep for 12 h. All sheep remained hemodynamically stable.

Conclusion

It is possible to ventilate four adult-human-sized sheep on a single ventilator for at least 12 h. This technique has the potential to improve disaster preparedness by expanding local ventilator surge capacity until emergency supplies can be delivered from central stockpiles. Further research should be conducted on ventilating individuals with different lung compliances and on potential microbial cross-contamination.

Introduction

The World Trade Center attacks, South and Central Asian Earthquakes, Indian Ocean Tsunami, SARS epidemic, and H5N1 influenza have focused attention on the need to provide care to large groups of patients during disasters. Public health planners and emergency and critical care providers have been particularly concerned about the availability of mechanical ventilation.1, 2, 3 This concern is based on experience with the 1918 influenza pandemic,⁴ 2001 anthrax attacks,⁵ 2003 SARS outbreak,⁵ and human H5N1 influenza cases,5, 6 which have all been characterized by rapidly progressive, severe, and often fatal respiratory failure.

Clinicians, ethicists, and public health officials have suggested rationing mechanical ventilation, providing manual ventilation, and stockpiling ventilators.2, 3, 7, 8 Each of these possible solutions are complex and variously limited by legal, monetary, physical, and human capital restraints.² A number of groups have proposed modifications of ventilator circuits that would permit a single ventilator to support multiple patients.9, 10, 11 In some cases, these adaptations have been tested using lung models and other simulators. No previous work has demonstrated the feasibility of multiple patient adaptations in a biologically relevant model using standard equipment. We conducted a study using four adult-human-sized sheep to test whether it is possible to provide mechanical ventilation to multiple patients using a single ventilator and commonly available equipment.

Section snippets

Study design

This study used a large animal (sheep) model to determine whether multiple adult patients can be ventilated simultaneously using a single ventilator. We chose sheep for several reasons, including the availability of adult-human-sized animals and our group's earlier experience working with this species.¹² Most importantly, sheep respiratory physiology is similar to human physiology13, 14 and the animals have been used to model respiratory changes in a variety of states, including pregnancy,¹⁴

Results

Base line respiratory and hemodynamic characteristics of the four subjects were similar except for sheep B which became apneic during induction and was resuscitated (Table 1).

Figure 2 graphs the subjects’ ventilatory status as measured by pCO₂ over 12 h. At the beginning of the experiment each subject had a very similar pCO₂ (range 37–43 mmHg). As the experiment progressed over the first 6 h, each supine subjects’ pCO₂ increased variably from baseline. At the end of the first quarter of the

Discussion

In this trial, our group demonstrated that it is possible to simultaneously ventilate four adult-human-sized sheep for at least 12 h using a single mechanical ventilator. We employed a circuit proposed by Neyman and Irvin⁹ and tested only with artificial lungs. Writers commenting on this system questioned whether it would function for anything more than “very short-term positive pressure ventilation augmentation.”²³ We believe that this trial begins to address these issues and is a significant

Conclusion

In this study, we demonstrated that it is possible to ventilate four adult-human-sized sheep on a single full-feature ventilator for at least 12 h. We employed standard equipment and an easy-to-construct circuit that was first tried in an artificial lung model.⁹ This technique has the potential to extend local ventilatory support resources until emergency supplies can be delivered. Further research should be conducted on differential lung compliance and microbial cross-contamination.

Conflict of interest

The authors have no conflicts of interest to disclose.

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Medical equipment can become scarce in disaster scenarios. Prior work has reported that four sheep could be ventilated together on a single ventilator. Others found that this maneuver is possible when needed, but no one has yet investigated whether cross-contamination occurs in co-ventilated individuals.
Our goal was to investigate whether an infection could spread between co-ventilated individuals.
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S. marcescens was not found in lung no. 2, 3, or 4 or the three additional sites on the expiratory limb at 24 and 48 h in all three trials.
Cross-contamination does not occur within 24 h using the described ventilator circuit configuration.
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pandemics are rare but devastating infectious calamities that rapidly and profoundly affect and transform human activity. the plague of the middle ages and more contemporary pandemics such as the 1918 h1n1 influenza, the human inmunodeficiency virus (hiv) and the coronavirus disease 2019 (covid-19) are just a few examples of these catastrophic events which have also significantly altered healthcare delivery and impacted the delvery of surgical care. the covid-19 is the most recent global pandemic, caused by the severe acute respiratory syndrome coronavirus 2 (sars-cov-2). transmitted by respiratory droplets and fomites, sars-cov-2 infection presents clinically with a multitude of symptoms, generally characterized as a “viral illness.” in some cases, symptoms can escalate into acute respiratory distress syndrome accompanied by a runaway inflammatory cytokine response and multiorgan failure. as public health concerns mounted as the covid-19 pandemic evolved, consecutive “waves” of infection caused millions of deaths around the globe. surgical specialties were among the most affected areas of medicine, with elective operations and surveillance diagnostics literally coming to a standstill. what followed was the orchestrated global effort to simultaneously address issues that were critical to restoring safe and “pandemic-proof” surgical (and other essential) services to meet ongoing population needs. this multi-pronged approach included the development of clinical patient risk stratification tools; clinical practice guidelines; ramping up of protective equipment, ventilator and air filtration device production; facility-level structural and workflow modifications; diagnostic testing/vaccine/antiviral development; as well as isolation, monitoring, respiratory/ventilator support, and post-discharge (e.g., rehab facility) infrastructure retooling. early in the covid-19 pandemic, critical shortages of personal protective equipment, hospital/icu beds/ventilators were further stressing the overburdened healthcare systems. ongoing challenges of social distancing, containment, isolation, and surge capacity issues across hospitals and clinics have led to rapid adoption of new technologies, such as telemedicine and web-based triage. implementation of social and physical isolation measures also caused sudden and deep economic hardship, with marked decreases in global trade and local small business activity alike. in this chapter, the current state-of-science, mitigation approaches, possible therapies, surgery-specific strategies, ethical considerations for healthcare workers and policymakers, as well as lessons learned from the covid-19 pandemic and the eventual return to a “new normal” are discussed. in addition, the authors hope that this information will be both important and relevant in the context of future outbreaks and pandemics.
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Citation Excerpt :
Furthermore, the disruption of the global supply chain prevents the movement and production of medical devices. The idea of using a single ventilator for multiple patients was introduced using six Briggs T‐tubes and a Puritan‐Bennett 840 Series ventilator which was tested in four sheep which contemplates human size [47,48]. The Briggs T-tube is a complex instrument not easily available in the past.
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Simulated ventilation of two patients with a single ventilator in a pandemic setting
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Design of a flow modulation device to facilitate individualized ventilation in a shared ventilator setup
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Development and assessment of the performance of a shared ventilatory system that uses clinically available components to individualize tidal volumes
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^☆: A Spanish translated version of the summary of this article appears as Appendix in the final online version at doi:10.1016/j.resuscitation.2007.10.016.

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Experimental paperIncreasing ventilator surge capacity in disasters: Ventilation of four adult-human-sized sheep on a single ventilator with a modified circuit☆

Summary

Objective

Methods

Results

Conclusion

Introduction

Section snippets

Study design

Results

Discussion

Conclusion

Conflict of interest

Ann Emerg Med

Resuscitation

Chest

Comp Biochem Physiol A

Disaster Manag Response

Br J Anaesth

Chest

Critical care during epidemics

Crit Care

Augmentation of hospital critical care capacity after bioterrorist attacks or epidemics: recommendations of the Working Group on Emergency Mass Critical Care

Crit Care Med

Positive-pressure ventilation equipment for mass casualty respiratory failure

Biosecur Bioterror

Flu: the story of the great influenza pandemic of 1918 and the search for the virus that caused it

Concept of operations for triage of mechanical ventilation in an epidemic

Acad Emerg Med

Avian influenza—a challenge to global health care structures

N Engl J Med

An argument for equipping civilian hospitals with a multiple respirator system for a chemical warfare mass casualty situation

Isr J Med Sci

Experimental paper
Increasing ventilator surge capacity in disasters: Ventilation of four adult-human-sized sheep on a single ventilator with a modified circuit☆