A single ventilator for multiple simulated patients to meet disaster surge

Quantitative Comparison of Ventilation Parameters of Different Approaches to Ventilator Splitting and Multiplexing

CONTEXT

Amid the COVID-19 pandemic, this study delves into ventilator shortages, exploring simple split ventilation (SSV), simple differential ventilation (SDV), and differential multiventilation (DMV). The knowledge gap centers on understanding their performance and safety implications.

HYPOTHESIS

Our hypothesis posits that SSV, SDV, and DMV offer solutions to the ventilator crisis. Rigorous testing was anticipated to unveil advantages and limitations, aiding the development of effective ventilation approaches.

METHODS AND MODELS

Using a specialized test bed, SSV, SDV, and DMV were compared. Simulated lungs in a controlled setting facilitated measurements with sensors. Statistical analysis honed in on parameters like peak inspiratory pressure (PIP) and positive end-expiratory pressure.

RESULTS

Setting target PIP at 15 cm H2O for lung 1 and 12.5 cm H2O for lung 2, SSV revealed a PIP of 15.67 ± 0.2 cm H2O for both lungs, with tidal volume (Vt) at 152.9 ± 9 mL. In SDV, lung 1 had a PIP of 25.69 ± 0.2 cm H2O, lung 2 at 24.73 ± 0.2 cm H2O, and Vts of 464.3 ± 0.9 mL and 453.1 ± 10 mL, respectively. DMV trials showed lung 1's PIP at 13.97 ± 0.06 cm H2O, lung 2 at 12.30 ± 0.04 cm H2O, with Vts of 125.8 ± 0.004 mL and 104.4 ± 0.003 mL, respectively.

INTERPRETATION AND CONCLUSIONS

This study enriches understanding of ventilator sharing strategy, emphasizing the need for careful selection. DMV, offering individualization while maintaining circuit continuity, stands out. Findings lay the foundation for robust multiplexing strategies, enhancing ventilator management in crises.

Design of a flow modulation device to facilitate individualized ventilation in a shared ventilator setup

This study aims to resolve the unmet need for ventilator surge capacity by developing a prototype device that can alter patient-specific flow in a shared ventilator setup. The device is designed to deliver a predictable tidal volume (VT), requiring minimal additional monitoring and workload. The prototyped device was tested in an in vitro bench setup for its performance against the intended use and design criteria. The ventilation parameters: VT and airway pressures, and ventilation profiles: pressure, flow and volume were measured for different ventilator and device settings for a healthy and ARDS simulated lung pathology. We obtained VTs with a linear correlation with valve openings from 10 to 100% across set inspiratory pressures (IPs) of 20 to 30 cmH2O. Airway pressure varied with valve opening and lung elastance but did not exceed set IPs. Performance was consistent in both healthy and ARDS-simulated lung conditions. The ventilation profile diverged from traditional pressure-controlled profiles. We present the design a flow modulator to titrate VTs in a shared ventilator setup. Application of the flow modulator resulted in a characteristic flow profile that differs from pressure- or volume controlled ventilation. The development of the flow modulator enables further validation of the Individualized Shared Ventilation (ISV) technology with individualization of delivered VTs and the development of a clinical protocol facilitating its clinical use during a ventilator surge capacity problem.

Mechanical Ventilation, Past, Present, and Future

Mechanical ventilation (MV) has played a crucial role in the medical field, particularly in anesthesia and in critical care medicine (CCM) settings. MV has evolved significantly since its inception over 70 years ago and the future promises even more advanced technology. In the past, ventilation was provided manually, intermittently, and it was primarily used for resuscitation or as a last resort for patients with severe respiratory or cardiovascular failure. The earliest MV machines for prolonged ventilatory support and oxygenation were large and cumbersome. They required a significant amount of skills and expertise to operate. These early devices had limited capabilities, battery, power, safety features, alarms, and therefore these often caused harm to patients. Moreover, the physiology of MV was modified when mechanical ventilators moved from negative pressure to positive pressure mechanisms. Monitoring systems were also very limited and therefore the risks related to MV support were difficult to quantify, predict and timely detect for individual patients who were necessarily young with few comorbidities. Technology and devices designed to use tracheostomies versus endotracheal intubation evolved in the last century too and these are currently much more reliable. In the present, positive pressure MV is more sophisticated and widely used for extensive period of time. Modern ventilators use mostly positive pressure systems and are much smaller, more portable than their predecessors, and they are much easier to operate. They can also be programmed to provide different levels of support based on evolving physiological concepts allowing lung-protective ventilation. Monitoring systems are more sophisticated and knowledge related to the physiology of MV is improved. Patients are also more complex and elderly compared to the past. MV experts are informed about risks related to prolonged or aggressive ventilation modalities and settings. One of the most significant advances in MV has been protective lung ventilation, diaphragm protective ventilation including noninvasive ventilation (NIV). Health care professionals are familiar with the use of MV and in many countries, respiratory therapists have been trained for the exclusive purpose of providing safe and professional respiratory support to critically ill patients. Analgo-sedation drugs and techniques are improved, and more sedative drugs are available and this has an impact on recovery, weaning, and overall patients' outcome. Looking toward the future, MV is likely to continue to evolve and improve alongside monitoring techniques and sedatives. There is increasing precision in monitoring global "patient-ventilator" interactions: structure and analysis (asynchrony, desynchrony, etc). One area of development is the use of artificial intelligence (AI) in ventilator technology. AI can be used to monitor patients in real-time, and it can predict when a patient is likely to experience respiratory distress. This allows medical professionals to intervene before a crisis occurs, improving patient outcomes and reducing the need for emergency intervention. This specific area of development is intended as "personalized ventilation." It involves tailoring the ventilator settings to the individual patient, based on their physiology and the specific condition they are being treated for. This approach has the potential to improve patient outcomes by optimizing ventilation and reducing the risk of harm. In conclusion, MV has come a long way since its inception, and it continues to play a critical role in anesthesia and in CCM settings. Advances in technology have made MV safer, more effective, affordable, and more widely available. As technology continues to improve, more advanced and personalized MV will become available, leading to better patients' outcomes and quality of life for those in need.

Development and assessment of the performance of a shared ventilatory system that uses clinically available components to individualize tidal volumes

OBJECTIVES

To develop and assess a system for shared ventilation using clinically available components to individualize tidal volumes.

DESIGN

Evaluation and in vitro validation study SETTING: Ventilator shortage during the SARS-CoV-2 pandemic.

PARTICIPANTS

The team consisted of physicians, bioengineers, computer programmers, and medical technology professionals.

METHODS

Using clinically available components, a system of ventilation consisting of two ventilatory limbs was assembled and connected to a ventilator. Monitors for each limb were developed using open-source software. Firstly, the effect of altering ventilator settings on tidal volumes delivered to each limb was determined. Secondly, the impact of altering the compliance and resistance of one limb on the tidal volumes delivered to both limbs was analysed. Experiments were repeated three times to determine system variability.

RESULTS

The system permitted accurate and reproducible titration of tidal volumes to each limb over a range of ventilator settings and simulated lung conditions. Alteration of ventilator inspiratory pressures, of respiratory rates, and I:E ratio resulted in very similar tidal volumes delivered to each limb. Alteration of compliance and resistance in one limb resulted in reproducible alterations in tidal volume to that test lung, with little change to tidal volumes in the other lung. All tidal volumes delivered were reproducible.

CONCLUSIONS

We demonstrate the reliability of a shared ventilation system assembled using commonly available clinical components that allows titration of individual tidal volumes. This system may be useful as a strategy of last resort for Covid-19, or other mass casualty situations, where the need for ventilators exceeds supply.

COVID-19 Lessons Learned: Response to the Anticipated Ventilator Shortage

Early in the COVID-19 pandemic predictions of a worldwide ventilator shortage prompted a worldwide search for solutions. The impetus for the scramble for ventilators was spurred on by inaccurate and often unrealistic predictions of ventilator requirements. Initial efforts looked simply at acquiring as many ventilators as possible from national and international sources. Ventilators from the Strategic National Stockpile were distributed to early hotspots in the Northeast and Northwest United States. In a triumph of emotion over logic, well-intended experts from other industries turned their time, talent, and treasure toward making a ventilator for the first time. Interest in shared ventilation (more than one patient per ventilator) was ignited by an ill-advised video on social media that ignored the principles of gas delivery in deference to social media notoriety. With shared ventilation, a number of groups mistook a physiologic problem for a plumbing problem. The United States government invoked the Defense Production Act to push automotive manufacturers to partner with existing ventilator manufacturers to speed production. The FDA granted emergency use authorization for "splitters" to allow shared ventilation as well as for ventilators and ancillary equipment. Rationing of ventilators was discussed in the lay press and medical literature but was never necessary in the US. Finally, planners realized that staff with expertise in providing mechanical ventilation were the most important shortage. Over 200,000 ventilators were purchased by the United States government, states, cities, health systems, and individuals. Most had little value in caring for patients with COVID-19 ARDS. This paper attempts to look at where miscalculations were made, with an eye toward what we can do better in the future.

Automatic air volume control system for ventilation of two patients using a single ventilator: a large animal model study

The COVID-19 pandemic outbreak led to a global ventilator shortage. Hence, various strategies for using a single ventilator to support multiple patients have been considered. A device called Ventil previously validated for independent lung ventilation was used in this study to evaluate its usability for shared ventilation. We performed experiments with a total number of 16 animals. Eight pairs of pigs were ventilated by a ventilator or anesthetic machine and by Ventil for up to 27 h. In one experiment, 200 ml of saline was introduced to one subject's lungs to reduce their compliance. The experiments were analyzed in terms of arterial blood gases and respiratory parameters. In addition to the animal study, we performed a series of laboratory experiments with artificial lungs (ALs). The resistance and compliance of one AL (affected) were altered, while the tidal volume (TV) and peak pressure (Ppeak) in the second (unaffected) AL were analyzed. In addition, to assess the risk of transmission of pathogens between AL respiratory tracts, laboratory tests were performed using phantoms of virus particles. The physiological level of analyzed parameters in ventilated animals was maintained, except for CO₂ tension, for which a permissive hypercapnia was indicated. Experiments did not lead to injuries in the animal's lungs except for one subject, as indicated by CT scan analysis. In laboratory experiments, changes in TV and Ppeak in the unaffected AL were less than 11%, except for 2 cases where the TV change was 20%. No cross-contamination was found in simulations of pathogen transmission. We conclude that ventilation using Ventil can be considered safe in patients undergoing deep sedation without spontaneous breathing efforts.

COVID-19: dealing with ventilator shortage

PURPOSE OF REVIEW

To describe different strategies adopted during coronavirus disease 2019 pandemic to cope with the shortage of mechanical ventilators.

RECENT FINDINGS

Short-term interventions aimed to increase ventilator supply and decrease demand. They included: redistributing and centralizing patients, repurposing operating rooms into intensive care units (ICUs) and boosting ventilator production and using stocks and back-ups; support by the critical care outreach team to optimize treatment of patients in the ward and permit early discharge from the ICU, ethical allocation of mechanical ventilators to patients who could benefit more from intensive treatment and short term ICU trials for selected patients with uncertain prognosis, respectively. Long-term strategies included education and training of non-ICU physicians and nurses to the care of critically-ill patients and measures to decrease viral spread among the population and the progression from mild to severe disease.

SUMMARY

The experience and evidence gained during the current pandemic is of paramount importance for physicians and law-makers to plan in advance an appropriate response to any future similar crisis. Intensive care unit, hospital, national and international policies can all be improved to build systems capable of treating an unexpectedly large number of patients, while keeping a high standard of safety.

Mohan D, Karganroudi SS. The Unprecedented Role of 3D Printing Technology in Fighting the COVID-19 Pandemic: A Comprehensive Review

The coronavirus disease 2019 (COVID-19) rapidly spread to over 180 countries and abruptly disrupted production rates and supply chains worldwide. Since then, 3D printing, also recognized as additive manufacturing (AM) and known to be a novel technique that uses layer-by-layer deposition of material to produce intricate 3D geometry, has been engaged in reducing the distress caused by the outbreak. During the early stages of this pandemic, shortages of personal protective equipment (PPE), including facemasks, shields, respirators, and other medical gear, were significantly answered by remotely 3D printing them. Amidst the growing testing requirements, 3D printing emerged as a potential and fast solution as a manufacturing process to meet production needs due to its flexibility, reliability, and rapid response capabilities. In the recent past, some other medical applications that have gained prominence in the scientific community include 3D-printed ventilator splitters, device components, and patient-specific products. Regarding non-medical applications, researchers have successfully developed contact-free devices to address the sanitary crisis in public places. This work aims to systematically review the applications of 3D printing or AM techniques that have been involved in producing various critical products essential to limit this deadly pandemic's progression.

Translational design for limited resource settings as demonstrated by Vent-Lock, a 3D-printed ventilator multiplexer

Background

Mechanical ventilators are essential to patients who become critically ill with acute respiratory distress syndrome (ARDS), and shortages have been reported due to the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).

Methods

We utilized 3D printing (3DP) technology to rapidly prototype and test critical components for a novel ventilator multiplexer system, Vent-Lock, to split one ventilator or anesthesia gas machine between two patients. FloRest, a novel 3DP flow restrictor, provides clinicians control of tidal volumes and positive end expiratory pressure (PEEP), using the 3DP manometer adaptor to monitor pressures. We tested the ventilator splitter circuit in simulation centers between artificial lungs and used an anesthesia gas machine to successfully ventilate two swine.

Results

As one of the first studies to demonstrate splitting one anesthesia gas machine between two swine, we present proof-of-concept of a de novo, closed, multiplexing system, with flow restriction for potential individualized patient therapy.

Conclusions

While possible, due to the complexity, need for experienced operators, and associated risks, ventilator multiplexing should only be reserved for urgent situations with no other alternatives. Our report underscores the initial design and engineering considerations required for rapid medical device prototyping via 3D printing in limited resource environments, including considerations for design, material selection, production, and distribution. We note that optimization of engineering may minimize 3D printing production risks but may not address the inherent risks of the device or change its indications. Thus, our case report provides insights to inform future rapid prototyping of medical devices.

Use of a novel "Split" ventilation system in bench and porcine modeling of acute respiratory distress syndrome

Split ventilation (using a single ventilator to ventilate multiple patients) is technically feasible. However, connecting two patients with acute respiratory distress syndrome (ARDS) and differing lung mechanics to a single ventilator is concerning. This study aimed to: (1) determine functionality of a split ventilation system in benchtop tests, (2) determine whether standard ventilation would be superior to split ventilation in a porcine model of ARDS and (3) assess usability of a split ventilation system with minimal specific training. The functionality of a split ventilation system was assessed using test lungs. The usability of the system was assessed in simulated clinical scenarios. The feasibility of the system to provide modified lung protective ventilation was assessed in a porcine model of ARDS (n = 30). In bench testing a split ventilation system independently ventilated two test lungs under conditions of varying compliance and resistance. In usability tests, a high proportion of naïve operators could assemble and use the system. In the porcine model, modified lung protective ventilation was feasible with split ventilation and produced similar respiratory mechanics, gas exchange and biomarkers of lung injury when compared to standard ventilation. Split ventilation can provide some elements of lung protective ventilation and is feasible in bench testing and an in vivo model of ARDS.

Model-based patient matching for in-parallel pressure-controlled ventilation

Background

Surges of COVID-19 infections have led to insufficient supply of mechanical ventilators (MV), resulting in rationing of MV care. In-parallel, co-mechanical ventilation (Co-MV) of multiple patients is a potential solution. However, due to lack of testing, there is currently no means to match ventilation requirements or patients, with no guidelines to date. In this research, we have developed a model-based method for patient matching for pressure control mode MV.

Methods

The model-based method uses a single-compartment lung model (SCM) to simulate the resultant tidal volume of patient pairs at a set ventilation setting. If both patients meet specified safe ventilation criteria under similar ventilation settings, the actual mechanical ventilator settings for Co-MV are determined via simulation using a double-compartment lung model (DCM). This method allows clinicians to analyse Co-MV in silico, before clinical implementation.

Results

The proposed method demonstrates successful patient matching and MV setting in a model-based simulation as well as good discrimination to avoid mismatched patient pairs. The pairing process is based on model-based, patient-specific respiratory mechanics identified from measured data to provide useful information for guiding care. Specifically, the matching is performed via estimation of MV delivered tidal volume (mL/kg) based on patient-specific respiratory mechanics. This information can provide insights for the clinicians to evaluate the subsequent effects of Co-MV. In addition, it was also found that Co-MV patients with highly restrictive respiratory mechanics and obese patients must be performed with extra care.

Conclusion

This approach allows clinicians to analyse patient matching in a virtual environment without patient risk. The approach is tested in simulation, but the results justify the necessary clinical validation in human trials.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12938-022-00983-y.

The Multi Split Ventilator System: Performance Testing of Respiratory Support Shared by Multiple Patients

Ventilator sharing has been proposed as a method of increasing ventilator capacity during instances of critical shortage. We sought to assess the ability of a regulated, shared ventilator system (Multi Split Ventilator System, MSVS) to individualize support to multiple simulated patients using one ventilator. We employed simulated patients of varying size, compliance, minute ventilation requirement, and PEEP requirement. Performance tests were performed to assess the ability of the QSVS, versus control, to achieve individualized respiratory goals to clinically disparate patients sharing a single ventilator following ARDSNet guidelines. Resilience tests measured the effects of simulated adverse events occurring to one patient on another patient sharing a single ventilator. The QSVS met individual oxygenation and ventilation requirements for multiple simulated patients with a tolerance similar to a single ventilator. Abrupt endotracheal tube occlusion or extubation occurring to one patient resulted in modest, clinically tolerable changes in ventilation parameters for the remaining patients. The QSVS is a regulated, shared ventilator system capable of individualizing ventilatory support to clinically dissimilar simulated patients. It is also resilient to common adverse events. The QSVS represents a feasible option to ventilate multiple patients during a severe ventilator shortage.

A computational fluid dynamics assessment of 3D printed ventilator splitters and restrictors for differential multi-patient ventilation

BACKGROUND

The global pandemic of novel coronavirus (SARS-CoV-2) has led to global shortages of ventilators and accessories. One solution to this problem is to split ventilators between multiple patients, which poses the difficulty of treating two patients with dissimilar ventilation needs. A proposed solution to this problem is the use of 3D-printed flow splitters and restrictors. There is little data available on the reliability of such devices and how the use of different 3D printing methods might affect their performance.

METHODS

We performed flow resistance measurements on 30 different 3D-printed restrictor designs produced using a range of fused deposition modelling and stereolithography printers and materials, from consumer grade printers using polylactic acid filament to professional printers using surgical resin. We compared their performance to novel computational fluid dynamics models driven by empirical ventilator flow rate data. This indicates the ideal performance of a part that matches the computer model.

RESULTS

The 3D-printed restrictors varied considerably between printers and materials to a sufficient degree that would make them unsafe for clinical use without individual testing. This occurs because the interior surface of the restrictor is rough and has a reduced nominal average diameter when compared to the computer model. However, we have also shown that with careful calibration it is possible to tune the end-inspiratory (tidal) volume by titrating the inspiratory time on the ventilator.

CONCLUSIONS

Computer simulations of differential multi patient ventilation indicate that the use of 3D-printed flow splitters is viable. However, in situ testing indicates that using 3D printers to produce flow restricting orifices is not recommended, as the flow resistance can deviate significantly from expected values depending on the type of printer used.

TRIAL REGISTRATION

Not applicable.

A Multiple Emergency Ventilator as Backup Solution in Pandemic: A Specifically Designed and Dimensioned Device

Goal: To provide a Multiple Emergency Ventilator (MEV) as backup in case of shortage of ICU ventilators and for use in camp hospitals. Methods: MEV provides the same oxygen mixture and peak inspiratory pressure (PIP) to 10 patients. These specifications were fixed: i) gas supply and plugs to double-limb intubation sets compatible to existing systems; ii) fluid-dynamics with no pressure drop and almost complete patients’ uncoupling; iii) individual monitoring of inspiratory and expiratory pressures and flows and control of their timing; iv) easy stocking, transport, installation with self-supporting pipes. Results: A Bell-Jar System (BJS) design permitted to safely fix PIP based on Archimedes’ law. The main distribution line was based on 2” stainless steel pipes assuring the required mechanical properties and over-dimensioned for fluidics. The Windkessel of the BJS and pipeline dead-volumes is 75.65 L and in the worst case of the instantaneous demand of 5 L by 10 patients (0.5 L each) shows an adiabatic PIP drop limited to –6.18%, confirming the needed uncoupling. Consequently, patients’ asynchrony is permitted as needed by pressure-controlled volume-guaranteed and assisted-ventilation. Conclusions: Although MEV is proposed as a backup system, its features may cover the whole set of ventilation modes required by ICU ventilation.

Pressure-Regulated Ventilator Splitting for Disaster Relief: Design, Testing, and Clinical Experience

The coronavirus disease 2019 (COVID-19) pandemic has revealed that even the best-resourced hospitals may lack sufficient ventilators to support patients under surge conditions. During a pandemic or mass trauma, an affordable, low-maintenance, off-the-shelf device that would allow health care teams to rapidly expand their ventilator capacity could prove lifesaving, but only if it can be safely integrated into a complex and rapidly changing clinical environment. Here, we define an approach to safe ventilator sharing that prioritizes predictable and independent care of patients sharing a ventilator. Subsequently, we detail the design and testing of a ventilator-splitting circuit that follows this approach and describe our clinical experience with this circuit during the COVID-19 pandemic. This circuit was able to provide individualized and titratable ventilatory support with individualized positive end-expiratory pressure (PEEP) to 2 critically ill patients at the same time, while insulating each patient from changes in the other's condition. We share insights from our experience using this technology in the intensive care unit and outline recommendations for future clinical applications.

Chemical Emissions from Cured and Uncured 3D-Printed Ventilator Patient Circuit Medical Parts

Medical shortages during the COVID-19 pandemic saw numerous efforts to 3D print personal protective equipment and treatment supplies. There is, however, little research on the potential biocompatibility of 3D-printed parts using typical polymeric resins as pertaining to volatile organic compounds (VOCs), which have specific relevance for respiratory circuit equipment. Here, we measured VOCs emitted from freshly printed stereolithography (SLA) replacement medical parts using proton transfer reaction mass spectrometry and infrared differential absorption spectroscopy, and particulates using a scanning mobility particle sizer. We observed emission factors for individual VOCs ranging from ∼0.001 to ∼10 ng cm-3 min-1. Emissions were heavily dependent on postprint curing and mildly dependent on the type of SLA resin. Curing reduced the emission of all observed chemicals, and no compounds exceeded the recommended dose of 360 μg/d. VOC emissions steadily decreased for all parts over time, with an average e-folding time scale (time to decrease to 1/e of the starting value) of 2.6 ± 0.9 h.

From hardware store to hospital: a COVID-19-inspired, cost-effective, open-source, in vivo-validated ventilator for use in resource-scarce regions

Resource-scarce regions with serious COVID-19 outbreaks do not have enough ventilators to support critically ill patients, and these shortages are especially devastating in developing countries. To help alleviate this strain, we have designed and tested the accessible low-barrier in vivo-validated economical ventilator (ALIVE Vent), a COVID-19-inspired, cost-effective, open-source, in vivo-validated solution made from commercially available components. The ALIVE Vent operates using compressed oxygen and air to drive inspiration, while two solenoid valves ensure one-way flow and precise cycle timing. The device was functionally tested and profiled using a variable resistance and compliance artificial lung and validated in anesthetized large animals. Our functional test results revealed its effective operation under a wide variety of ventilation conditions defined by the American Association of Respiratory Care guidelines for ventilator stockpiling. The large animal test showed that our ventilator performed similarly if not better than a standard ventilator in maintaining optimal ventilation status. The FiO₂, respiratory rate, inspiratory to expiratory time ratio, positive-end expiratory pressure, and peak inspiratory pressure were successfully maintained within normal, clinically validated ranges, and the animals were recovered without any complications. In regions with limited access to ventilators, the ALIVE Vent can help alleviate shortages, and we have ensured that all used materials are publicly available. While this pandemic has elucidated enormous global inequalities in healthcare, innovative, cost-effective solutions aimed at reducing socio-economic barriers, such as the ALIVE Vent, can help enable access to prompt healthcare and life saving technology on a global scale and beyond COVID-19.

Sharing Mechanical Ventilator: In Vitro Evaluation of Circuit Cross-Flows and Patient Interactions

During the COVID-19 pandemic, a shortage of mechanical ventilators was reported and ventilator sharing between patients was proposed as an ultimate solution. Two lung simulators were ventilated by one anesthesia machine connected through two respiratory circuits and T-pieces. Five different combinations of compliances (30–50 mL × cmH₂O⁻¹) and resistances (5–20 cmH₂O × L⁻¹ × s⁻¹) were tested. The ventilation setting was: pressure-controlled ventilation, positive end-expiratory pressure 15 cmH₂O, inspiratory pressure 10 cmH₂O, respiratory rate 20 bpm. Pressures and flows from all the circuit sections have been recorded and analyzed. Simulated patients with equal compliance and resistance received similar ventilation. Compliance reduction from 50 to 30 mL × cmH₂O⁻¹ decreased the tidal volume (V_T) by 32% (418 ± 49 vs. 285 ± 17 mL). The resistance increase from 5 to 20 cmH₂O × L⁻¹ × s⁻¹ decreased V_T by 22% (425 ± 69 vs. 331 ± 51 mL). The maximal alveolar pressure was lower at higher compliance and resistance values and decreased linearly with the time constant (r² = 0.80, p < 0.001). The minimum alveolar pressure ranged from 15.5 ± 0.04 to 16.57 ± 0.04 cmH₂O. Cross-flows between the simulated patients have been recorded in all the tested combinations, during both the inspiratory and expiratory phases. The simultaneous ventilation of two patients with one ventilator may be unable to match individual patient’s needs and has a high risk of cross-interference.

Multiplex Ventilation: Solutions for Four Main Safety Problems

BACKGROUND

The COVID-19 pandemic has led to an increased demand for mechanical ventilators and concerns of a ventilator shortage. Several groups have advocated for 1 ventilator to ventilate 2 or more patients in the event of such a shortage. However, differences in patient lung mechanics could make sharing a ventilator detrimental to both patients. Our previous study indicated failure to ventilate in 67% of simulations. The safety problems that must be solved include individual control of tidal volume (V_T), individual measurement of V_T, individualization of PEEP settings, and individual PEEP measurement. The purpose of this study was to evaluate potential solutions developed at our institution.

METHODS

Two separate lung simulators were ventilated with a modified multiplex circuit using pressure control ventilation. Parameters of the lung models used for simulations (resistance and compliance) were evidence-based from published studies. Individual circuit-modification devices were first evaluated for accuracy. Devices were an adjustable flow diverter valve, a prototype dual volume display, a PEEP valve, and a disposable PEEP display. Then the full modified multiplex circuit was assessed by ventilating 6 pairs of simulated patients with different lung models and attempting to equalize ventilation. Ventilation was considered equalized when V_T and end-expiratory lung volume were within 10% for each simulation.

RESULTS

The adjustable flow diverter valve allowed volume adjustment to 1 patient without affecting the other. The average error of the dual volume display was -17%. The PEEP valves individualized PEEP, but the PEEP gauge error ranged from 17% to 41%. Using the multiplex circuit, ventilation was equalized regardless of differences in resistance or compliance, reversing the "failure modes" of our previous study.

CONCLUSIONS

The results of this simulation-based study indicate that devices for individual control and display of V_T and PEEP are effective in extending the usability and potential patient safety of multiplex ventilation.

The rise of 3D Printing entangled with smart computer aided design during COVID-19 era

During the current Pandemic, seven and a half million flights worldwide were canceled which disrupted the supply chain of all types of goods such as, personal protective gears, medical health devices, raw materials, food, and other essential equipments. The demand for health and medical related goods increased during this period globally, while the production using classical manufacturing techniques were effected because of the lockdowns and disruption in the transporation system. This created the need of geo scattered, small, and rapid manufacturing units along with a smart computer aided design (CAD) facility. The availability of 3D printing technologies and open source CAD design made it possible to overcome this need. In this article, we present an extensive review on the utilization of 3D printing technology in the days of pandamic. We observe that 3D printing together with smart CAD design show promise to overcome the disruption caused by the lockdown of classical manufacturing units specially for medical and testing equipment, and protective gears. We observe that there are several short communications, commentaries, correspondences, editorials and mini reviews compiled and published; however, a systematic state-of-the-art review is required to identify the significance of 3D printing, design for additive manufacturing (AM), and digital supply chain for handling emergency situations and in the post-COVID era. We present a review of various benefits of 3DP particularly in emergency situations such as a pandemic. Furthermore, some relevant iterative design and 3DP case studies are discussed systematically. Finally, this article highlights the areas that can help to control the emergency situation such as a pandemic, and critically discusses the research gaps that need further research in order to exploit the full potential of 3DP in pandemic and post-pandemic future era.

Additive manufacturing and the COVID-19 challenges: An in-depth study

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) rapidly achieved global pandemic status. The pandemic created huge demand for relevant medical and personal protective equipment (PPE) and put unprecedented pressure on the healthcare system within a very short span of time. Moreover, the supply chain system faced extreme disruption as a result of the frequent and severe lockdowns across the globe. In such a situation, additive manufacturing (AM) becomes a supplementary manufacturing process to meet the explosive demands and to ease the health disaster worldwide. Providing the extensive design customization, a rapid manufacturing route, eliminating lengthy assembly lines and ensuring low manufacturing lead times, the AM route could plug the immediate supply chain gap, whilst mass production routes restarted again. The AM community joined the fight against COVID-19 by producing components for medical equipment such as ventilators, nasopharyngeal swabs and PPE such as face masks and face shields. The aim of this article is to systematically summarize and to critically analyze all major efforts put forward by the AM industry, academics, researchers, users, and individuals. A step-by-step account is given summarizing all major additively manufactured products that were designed, invented, used, and produced during the pandemic in addition to highlighting some of the potential challenges. Such a review will become a historical document for the future as well as a stimulus for the next generation AM community.

2020 Year in Review: Shared Ventilation for COVID-19

COVID-19 resulting from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has resulted in a pandemic of respiratory failure previously unencountered. Early in the pandemic, concentrated infections in high-density population cities threatened to overwhelm health systems, and ventilator shortages were predicted. An early proposed solution was the use of shared ventilation, or the use of a single ventilator to support ≥ 2 patients. Spurred by ill-conceived social media posts, the idea spread in the lay press. Prior to 2020, there were 7 publications on this topic. A year later, more than 40 publications have addressed the technical details for shared ventilation, clinical experience with shared ventilation, as well as the numerous limitations and ethics of the technique. This is a review of the literature regarding shared ventilation from peer-reviewed articles published in 2020.

Innovation in a Time of Crisis: A Systematic Review of Three-Dimensional Printing in the COVID-19 Pandemic

The coronavirus (COVID-19) global pandemic resulted in the breakdown of traditional supply chains responsible for providing essential equipment to hospitals and personal protective equipment (PPE) for health and social care workers. The three-dimensional (3D) printing community has responded to emerging need by recognizing shortages across health care systems and providing innovative solutions in real time, circumventing short-term global supply issues. A systematic review was undertaken to investigate the role of 3D printing in the COVID-19 pandemic in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines using the MEDLINE, EMBASE, and World Health Organization (WHO) COVID-19 databases. Newspaper and internet article sources were identified using the NEXIS media database. All studies and articles on the application of 3D printed solutions during the peak of the COVID-19 pandemic were included. The literature search identified 26 related articles, and 13 studies met inclusion criteria and were suitable for full-text review. One thousand two hundred and one unique digital media articles were identified; after removal of duplicates and screening of headlines for the inclusion and exclusion criteria, 460 articles were suitable for full-text review. The cross-collaboration between the 3D printing community and health care systems has aided in the provision of innovative solutions to combat the COVID-19 crisis. The applications for 3D printing ranged from oxygenation equipment to noninvasive and invasive ventilatory parts and innovative solutions for infection control and quarantine hubs. This review has identified that 3D printing technology has made the biggest contribution to the production of PPE in particular face shields, mirroring the areas of greatest shortage and need. Additive manufacturing has played a pivotal role in aligning disciplines in engineering, science, and medicine for the greater good. We have witnessed the rapid reconfiguration of traditional supply chains to circumvent global shortages, while making advancements in effort to limit the impact of this and future pandemics.

Possible solutions for oxygenation support in critically ill patients with COVID-19

Purpose

Due to the large number of patients with respiratory deficiency during the COVID-19 pandemic, several governments and their respective health care services have been studying ways to complement the care provided by offering immediate solutions. In view of this, the aim of this study was to carry out a systematic review of the advantages and disadvantages of possible solutions in oxygenation support.

Methods

This systematic review used the PRISMA-P methodology and sought to list alternatives in oxygenation support that are being applied and studied worldwide. A bibliographic search was conducted in the MEDLINE and Cochrane Central databases, using the keywords SARS-CoV-2, COVID19, or coronavirus; combined with extracorporeal membrane oxygenation (ECMO), mechanical ventilation, mechanical ventilation support, low-cost, anesthesia, anesthesia machine, and ventilation therapy. The records were also found in the gray literature.

Results

The search found 85 publications of which 41 articles were considered after excluding duplicate articles, reading the title and summary, and reading the articles in full. The oxygenation supports identified in these publications were the following: ECMO, shared mechanical ventilator, fast or low-cost production equipment, high-flow nasal cannula (HFNC), non-invasive ventilation, and use of anesthesia equipment as a mechanical ventilator.

Conclusion

This study demonstrated the importance of a trained clinical team in the application of technologies. The alternatives found for support oxygenation require a more robust clinical evaluation to demonstrate their efficacy and safety for the COVID-19 patient.

Development of a multi-patient ventilator circuit with validation in an ARDS porcine model

Purpose

The COVID-19 pandemic threatens our current ICU capabilities nationwide. As the number of COVID-19 positive patients across the nation continues to increase, the need for options to address ventilator shortages is inevitable. Multi-patient ventilation (MPV), in which more than one patient can use a single ventilator base unit, has been proposed as a potential solution to this problem. To our knowledge, this option has been discussed but remains untested in live patients with differing severity of lung pathology.

Methods

The objective of this study was to address ventilator shortages and patient stacking limitations by developing and validating a modified breathing circuit for two patients with differing lung compliances using simple, off-the-shelf components. A multi-patient ventilator circuit (MPVC) was simulated with a mathematical model and validated with four animal studies. Each animal study had two human-sized pigs: one healthy and one with lipopolysaccharide (LPS) induced ARDS. LPS was chosen because it lowers lung compliance similar to COVID-19. In a previous study, a control group of four pigs was given ARDS and placed on a single patient ventilation circuit (SPVC). The oxygenation of the MPVC ARDS animals was then compared to the oxygenation of the SPVC animals.

Results

Based on the comparisons, similar oxygenation and morbidity rates were observed between the MPVC ARDS animals and the SPVC animals.

Conclusion

As healthcare systems worldwide deal with inundated ICUs and hospitals from pandemics, they could potentially benefit from this approach by providing more patients with respiratory care.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00540-021-02948-2.

Development of a Critical Care Response - Experiences from Italy During the Coronavirus Disease 2019 Pandemic

Italy was the first western country facing an outbreak of coronavirus disease 2019 (COVID-19). The first Italian patient diagnosed with COVID-19 was admitted, on Feb. 20, 2020, to the intensive care unit (ICU) in Codogno (Lodi, Lombardy, Italy), and the number of reported positive cases increased to 36 in the next 24 hours, and then exponentially for 18 days. This triggered a response that resulted in a massive surge in ICU bed capacity. The COVID19 Lombardy Network organized a structured logistic response and provided scientific evidence to highlight information on COVID-19 associated respiratory failure.

Exhalatory dynamic interactions between patients connected to a shared ventilation device

In this work a shared pressure-controlled ventilation device for two patients is considered. By the use of different valves incorporated to the circuit, the device enables the restriction of possible cross contamination and the individualization of tidal volumes, driving pressures, and positive end expiratory pressure PEEP. Possible interactions in the expiratory dynamics of different pairs of patients are evaluated in terms of the characteristic exhalatory times. These characteristic times can not be easily established using simple linear lumped element models. For this purpose, a 1D model using the Hydraulic and Mechanical libraries in Matlab Simulink was developed. In this sense, experiments accompany this study to validate the model and characterize the different valves of the circuit. Our results show that connecting two patients in parallel to a ventilator always resulted in delays of time during the exhalation. The size of this effect depends on different parameters associated with the patients, the circuit and the ventilator. The dynamics of the exhalation of both patients is determined by the ratios between patients exhalatory resistances, compliances, driving pressures and PEEPs. Adverse effects on exhalations became less noticeable when respiratory parameters of both patients were similar, flow resistances of valves added to the circuit were negligible, and when the ventilator exhalatory valve resistance was also negligible. The asymmetries of driving pressures, compliances or resistances exacerbated the possibility of auto-PEEP and the increase in relaxation times became greater in one patient than in the other. In contrast, exhalatory dynamics were less sensitive to the ratio of PEEP imposed to the patients.

Titration of Parameters in Shared Ventilation With a Portable Ventilator

BACKGROUND

Dual-patient, single-ventilator protocols (ie, protocols to ventilate 2 patients with a single conventional ventilator) may be required in times of crisis. This study demonstrates a means to titrate peak inspiratory pressure (PIP), PEEP, and [Formula: see text] for test lungs ventilated via a dual-patient, single-ventilator circuit.

METHODS

This prospective observational study was conducted using a ventilator connected to 2 test lungs. Changes in PIP, PEEP, and [Formula: see text] were made to the experimental lung, while no changes were made to the control lung. Measurements were obtained simultaneously from each test lung. PIP was titrated using 3D-printed resistors added to the inspiratory circuit. PEEP was titrated using expiratory circuit tubing with an attached manual PEEP valve. [Formula: see text] was titrated by using a splitter added to the ventilator tubing.

RESULTS

PIP, PEEP, and [Formula: see text] were reliably and incrementally titratable in the experimental lung, with some notable but manageable changes in pressure and [Formula: see text] documented in the control lung during these titrations. Similar results were measured in lungs with identical and different compliances.

CONCLUSIONS

Pressures and [Formula: see text] can be reliably adjusted when utilizing a dual-patient, single-ventilator circuit with simple, low-cost modifications to the circuit. This innovation could potentially be lifesaving in a resource-limited or crisis setting. Understanding the interactions of these circuits is imperative for making their use safer.

A Spatiotemporal Tool to Project Hospital Critical Care Capacity and Mortality From COVID-19 in US Counties

Objectives. To create a tool to rapidly determine where pandemic demand for critical care overwhelms county-level surge capacity and to compare public health and medical responses.Methods. In March 2020, COVID-19 cases requiring critical care were estimated using an adaptive metapopulation SEIR (susceptible‒exposed‒infectious‒recovered) model for all 3142 US counties for future 21-day and 42-day periods from April 2, 2020, to May 13, 2020, in 4 reactive patterns of contact reduction-0%, 20%, 30%, and 40%-and 4 surge response scenarios-very low, low, medium, and high.Results. In areas with increased demand, surge response measures could avert 104 120 additional deaths-55% through high clearance of critical care beds and 45% through measures such as greater ventilator access. The percentages of lives saved from high levels of contact reduction were 1.9 to 4.2 times greater than high levels of hospital surge response. Differences in projected versus actual COVID-19 demands were reasonably small over time.Conclusions. Nonpharmaceutical public health interventions had greater impact in minimizing preventable deaths during the pandemic than did hospital critical care surge response. Ready-to-go spatiotemporal supply and demand data visualization and analytics tools should be advanced for future preparedness and all-hazards disaster response.

Increasing the efficiency of mechanical ventilators during pandemics through additive manufacturing

The COVID-19 pandemic tested medical facilities' readiness in terms of the number of available mechanical ventilators. Most countries raced to stock up on ventilators, which created a surge in demand and short in supply. Furthermore, other means of coping with the demand were proposed, such as using additive manufacturing. The purpose of this paper was to test whether the addition of 3D-printed splitters would help deliver required tidal volume to each patient, while supporting four patients on a single ventilator for 24 hours on pressure mode at 25-cm H2O, and to determine whether a fifth patient can be ventilated. The ventilation of four human lungs was simulated using 3D printed parts, a single ventilator, four test-lungs, and standard tubing. Peak pressure, positive end-expiratory pressure, total tidal volume, individual tidal volume, total minute volume, and individual tidal volume data were collected. Usage of a 3D printed small size splitter enabled a 26% increase in individual tidal volume compared to standard tubing and a series of two-way splitters. The ventilator was able to supply the required pressure and tidal volume for 24 hours. A single ventilator with a four-way splitter can ventilate four patients experiencing respiratory failure for at least 24 hours without interruption. The equipment cannot sustain ventilating a fifth patient owing to minute volume limitation. This study expands on an earlier study that tested similar circuitry and reveals that the desired individual tidal volume is achieved. However, further research is required to provide the monitoring ability of individual patient parameters and prevention of cross-contamination.

Preparing Intensive Care Unit in Resource-Constraint Setting Amid COVID-19 Pandemic: Our Experience and Review

COVID-19 pandemic is an emerging, rapidly evolving public health emergency where a nation's health-care system can face a marked surge in demand for intensive care unit (ICU) beds and organ support. In regions with insufficient medical resources, it may further aggravate the existing shortage, limiting an ICU's ability to provide the normal standard of care. It can present ethically or legally demanding questions about how to prioritize the allocation of life-saving medical resources. In developing countries like India, still many hospitals are challenged by competing priorities and remain underprepared. In the wake of COVID-19 pandemic, to guide the intensive care disaster planners in regions with low resources and to ensure ICU readiness, this review shares our experience and strategies for preparing ICU with existing and alternative resources, focusing on space, equipment, and health-care workers’ safety and training.

Mechanical-Ventilation Supply and Options for the COVID-19 Pandemic. Leveraging All Available Resources for a Limited Resource in a Crisis

The novel coronavirus disease (COVID-19) has exposed critical supply shortages both in the United States and worldwide, including those in intensive care unit (ICU) and hospital bed supply, hospital staff, and mechanical ventilators. Many of those who are critically ill have required days to weeks of supportive invasive mechanical ventilation (IMV) as part of their treatment. Previous estimates set the U.S. availability of mechanical ventilators at approximately 62,000 full-featured ventilators, with 98,000 non–full-featured devices (including noninvasive devices). Given the limited availability of this resource both in the United States and in low- and middle-income countries, we provide a framework to approach the shortage of IMV resources. Here we discuss evidence and possibilities to reduce overall IMV needs, discuss strategies to maximize the availability of IMV devices designed for invasive ventilation, discuss the underlying methods in the literature to create and fashion new sources of potential ventilation that are available to hospitals and front-line providers, and discuss the staffing needs necessary to support IMV efforts. The pandemic has already pushed cities like New York and Boston well beyond previous ICU capacity in its first wave. As hot spots continue to develop around the country and the globe, it is evident that issues may arise ahead regarding the efficient and equitable use of resources. This unique challenge may continue to stretch resources and require care beyond previously set capacities and boundaries. The approaches presented here provide a review of the known evidence and strategies for those at the front line who are facing this challenge.

Emergency 3-Dimensional-Printed Devices for Splitting Ventilators in Lungs With Different Compliances: An In Vitro Study

Ventilator shortages occurred due to the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). This in vitro study evaluated the effectiveness of 3-dimensional (3D)-printed splitters and 3D-printed air flow limiters (AFL) in delivering appropriate tidal volumes (TV) to lungs with different compliances. Groups were divided according to the size of the AFL: AFL-4 was a 4-mm device, AFL-5 a 5-mm device, AFL-6 a 6-mm device, and no limiter (control). A ventilator was split to supply TV to 2 artificial lungs with different compliances. The AFL improved TV distribution.

Evaluating cross contamination on a shared ventilator

BACKGROUND

Disasters have the potential to cause critical shortages of life-saving equipment. It has been postulated that during patient surge, multiple individuals could be maintained on a single ventilator. This was supported by a previous trial that showed one ventilator could support four sheep. The goal of our study is to investigate if cross contamination of pathological agents occurs between individuals on a shared ventilator with strategically placed antimicrobial filters.

METHODS

A multipatient ventilator circuit was assembled using four sterile, parallel standard tubing circuits attached to four 2 L anaesthesia bags, each representing a simulated patient. Each 'patient' was attached to a Heat and Moisture Exchange filter. An additional bacterial/viral filter was attached to each expiratory limb. 'Patient-Lung' number 1 was inoculated with an isolate of Serratia marcescens, and the circuit was run for 24 hours. Each 'lung' and three points in the expiratory limb tubing were washed with broth and cultured. All cultures were incubated for 48 hours with subcultures performed at 24 hours.

RESULTS

Washed cultures of patient 2, 3 and 4 failed to demonstrate growth of S. marcescens. Cultures of the distal expiratory tubing, expiratory limb connector and expiratory limb prefilter tubing yielded no growth of S. marcescens at 24 or 48 hours.

CONCLUSION

Based on this circuit configuration, it is plausible to maintain four individuals on a single ventilator for 24 hours without fear of cross contamination.

Use of capnography to verify emergency ventilator sharing in the COVID-19 era

Exacerbation of COVID-19 pandemic may lead to acute shortage of ventilators, which may require shared use of ventilator as a lifesaving concept. Two model lungs were ventilated with one ventilator to i) test the adequacy of individual tidal volumes via capnography, ii) assess cross-breathing between lungs, and iii) offer a simulation-based algorithm for ensuring equal tidal volumes. Ventilation asymmetry was induced by placing rubber band around one model lung, and the uneven distribution of tidal volumes (VT) was counterbalanced by elevating airflow resistance (HR) contralaterally. VT, end-tidal CO2 concentration (ETCO2), and peak inspiratory pressure (Ppi) were measured. Unilateral LC reduced VT and elevated ETCO2 on the affected side. Under HR, VT and ETCO2 were re-equilibrated. In conclusion, capnography serves as simple, bedside method for controlling the adequacy of split ventilation in each patient. No collateral gas flow was observed between the two lungs with different time constants. Ventilator sharing may play a role in emergency situations.

The role of 3D printing in the fight against COVID-19 outbreak

Along with the COVID-19 pandemic, urgent needs for medical and specialized products, especially personal protective equipment, has been overwhelming. The conventional production line of medical devices has been challenged by excessive global demand, and the need for an easy, low-cost and rapid fabrication method is felt more than ever. In a scramble to address this shortfall, manufacturers referred to additive manufacturing or 3D printing to fill the gap and increase the production line of medical devices. Various previously/conventionally fabricated designs have been modified and redesigned to suit the 3D printing requirement to fight against COVID-19. In this perspective, various designs accommodated for the current worldwide outbreak of COVID-19 are discussed and how 3D printing could help the global community against the current and future conditions has been explored.

A Crisis-Responsive Framework for Medical Device Development Applied to the COVID-19 Pandemic

The disruption of conventional manufacturing, supply, and distribution channels during the COVID-19 pandemic caused widespread shortages in personal protective equipment (PPE) and other medical supplies. These shortages catalyzed local efforts to use nontraditional, rapid manufacturing to meet urgent healthcare needs. Here we present a crisis-responsive design framework designed to assist with product development under pandemic conditions. The framework emphasizes stakeholder engagement, comprehensive but efficient needs assessment, rapid manufacturing, and modified product testing to enable accelerated development of healthcare products. We contrast this framework with traditional medical device manufacturing that proceeds at a more deliberate pace, discuss strengths and weakness of pandemic-responsive fabrication, and consider relevant regulatory policies. We highlight the use of the crisis-responsive framework in a case study of face shield design and production for a large US academic hospital. Finally, we make recommendations aimed at improving future resilience to pandemics and healthcare emergencies. These include continued development of open source designs suitable for rapid manufacturing, education of maker communities and hospital administrators about rapidly-manufactured medical devices, and changes in regulatory policy that help strike a balance between quality and innovation.

Novel additive manufacturing applications for communicable disease prevention and control: focus on recent COVID-19 pandemic

COVID-19 disease caused by the SARS-CoV-2 virus has had serious adverse effects globally in 2020 which are foreseen to extend in 2021, as well. The most important of these effects was exceeding the capacity of the healthcare infrastructures, and the related inability to meet the need for various medical equipment especially within the first months of the crisis following the emergence and rapid spreading of the virus. Urgent global demand for the previously unavailable personal protective equipment, sterile disposable medical supplies as well as the active molecules including vaccines and drugs fueled the need for the coordinated efforts of the scientific community. Amid all this confusion, the rapid prototyping technology, 3D printing, has demonstrated its competitive advantage by repositioning its capabilities to respond to the urgent need. Individual and corporate, amateur and professional all makers around the world with 3D printing capacity became united in effort to fill the gap in the supply chain until mass production is available especially for personal protective equipment and other medical supplies. Due to the unexpected, ever-changing nature of the COVID-19 pandemic-like all other potential communicable diseases-the need for rapid design and 3D production of parts and pieces as well as sterile disposable medical equipment and consumables is likely to continue to keep its importance in the upcoming years. This review article summarizes how additive manufacturing technology can contribute to such cases with special focus on the recent COVID-19 pandemic.

Preparedness of ICU networks for pandemics

PURPOSE OF REVIEW

The recent COVID-19 outbreak has clearly shown how epidemics/pandemics can challenge developed countries' healthcare systems. Proper management of equipment and human resources is critical to provide adequate medical care to all patients admitted to the hospital and the ICU for both pandemic-related and unrelated reasons.

RECENT FINDINGS

Appropriate separate paths for infected and noninfected patients and prompt isolation of infected critical patients in dedicated ICUs play a pivotal role in limiting the contagions and optimizing resources during pandemics. The key to handle these challenging events is to learn from past experiences and to be prepared for future occurrences. Hospital space should be redesigned to quickly increase medical and critical care capacity, and healthcare workers (critical and noncritical) should be trained in advance.

SUMMARY

A targeted improvement of hospital and ICU protocols will increase medical care quality for patients admitted to the hospital for any clinical reasons during a pandemic.

Bubble CPAP splitting: innovative strategy in resource-limited settings

BACKGROUND

Non-invasive respiratory support for neonates using bubble continuous positive airway pressure (bCPAP) delivery systems is now widespread owing to its safety, cost effectiveness and easy applicability. Many innovative solutions have been suggested to deal with the possible shortage in desperate situations like disasters, pandemics and resource-limited settings. Although splitting of invasive ventilation has been reported previously, no attempts to split non-invasive respiratory support have been reported.

OBJECTIVE

The primary objective was to test the feasibility of splitting the bCPAP assembly using a T-piece splitter in a simulation model.

METHODS

A pilot simulation-based study was done to split a single bCPAP assembly using a T-piece. Other materials consisted of a heated humidification system, an air oxygen blender, corrugated inspiratory and expiratory tubing, nasal interfaces and two intercostal chest tube drainage bags. Two pressure manometers were used simultaneously to measure delivered pressures at different levels of set bCPAPs at the expiratory limb of nasal interfaces.

RESULTS

Pressures measured at the expiratory end of two nasal interfaces were 5.1 and 5.2 cm H2O, respectively, at a flow of 6 L/min and a water level of 5 cm H2O in both chest bags. When tested across different levels of set continuous positive airway pressure (3-8 cmH2O) and fractional inspired oxygen concentration (0.30-1.0), measured parameters corresponded to set parameters.

CONCLUSION

bCPAP splitting using a T-piece splitter is a technically simple, feasible and reliable strategy tested in a simulation model. Further testing is needed in a simulated lung model.

Simultaneous ventilation in the Covid-19 pandemic. A bench study

COVID-19 pandemic sets the healthcare system to a shortage of ventilators. We aimed at assessing tidal volume (V_T) delivery and air recirculation during expiration when one ventilator is divided into 2 test-lungs. The study was performed in a research laboratory in a medical ICU of a University hospital. An ICU (V500) and a lower-level ventilator (Elisée 350) were attached to two test-lungs (QuickLung) through a dedicated flow-splitter. A 50 mL/cmH₂O Compliance (C) and 5 cmH₂O/L/s Resistance (R) were set in both A and B test-lungs (A C50R5 / B C50R5, step1), A C50-R20 / B C20-R20 (step 2), A C20-R20 / B C10-R20 (step 3), and A C50-R20 / B C20-R5 (step 4). Each ventilator was set in volume and pressure control mode to deliver 800mL V_T. We assessed V_T from a pneumotachograph placed immediately before each lung, pendelluft air, and expiratory resistance (circuit and valve). Values are median (1^st-3^rd quartiles) and compared between ventilators by non-parametric tests. Between Elisée 350 and V500 in volume control V_T in A/B test- lungs were 381/387 vs. 412/433 mL in step 1, 501/270 vs. 492/370 mL in step 2, 509/237 vs. 496/332 mL in step 3, and 496/281 vs. 480/329 mL in step 4. In pressure control the corresponding values were 373/336 vs. 430/414 mL, 416/185 vs. 322/234 mL, 193/108 vs. 176/ 92 mL and 422/201 vs. 481/329mL, respectively (P<0.001 between ventilators at each step for each volume). Pendelluft air volume ranged between 0.7 to 37.8 ml and negatively correlated with expiratory resistance in steps 2 and 3. The lower-level ventilator performed closely to the ICU ventilator. In the clinical setting, these findings suggest that, due to dependence of V_T to C, pressure control should be preferred to maintain adequate V_T at least in one patient when C and/or R changes abruptly and monitoring of V_T should be done carefully. Increasing expiratory resistance should reduce pendelluft volume.

The Multisplit Ventilator System: Design and Function of a Regulated, Shared Ventilator System

The objective of this paper is to describe the design and function of the multisplit ventilator system (MSVS); an airflow apparatus that enables physicians to provide individualized, isolated ventilation to up to four patients using a single ventilator. Method: The study design is laboratory assessment of the ability of the MSVS to decouple the pressures and resulting tidal volumes between patient limbs in response to adverse extubation (disconnection) or endotracheal tube occlusion of one of the patients in the system. We compare the airflow decoupling of the MSVS against an existing unregulated split ventilator system (USVS) design over eight prototypical patient pairs. Simulated patient prototypes of varying size, minute ventilation requirement, and positive end-expiratory pressure (PEEP) requirement were employed. Result: Respiratory support was developed for varying simulated patient pairs using the MSVS and a USVS. The results demonstrate that patients supported with the MSVS showed significantly smaller changes to tidal volume and PEEP after extubation events, and tidal volume after occlusion events. Conclusion: It was found that the MSVS as a regulated, shared ventilator system effectively buffered simulated patients from clinical changes occurring to another patient connected to the split ventilator. This decoupling ability resulted in significantly smaller changes in delivered support when compared to existing USVS designs, which is an important patient safety consideration if deciding to support multiple patients with a single ventilator.

Answering the Challenge of COVID-19 Pandemic Through Innovation and Ingenuity

The novel coronavirus disease 2019 (COVID-19) pandemic has created a maelstrom of challenges affecting virtually every aspect of global healthcare system. Critical hospital capacity issues, depleted ventilator and personal protective equipment stockpiles, severely strained supply chains, profound economic slowdown, and the tremendous human cost all culminated in what is questionably one of the most profound challenges that humanity faced in decades, if not centuries. Effective global response to the current pandemic will require innovation and ingenuity. This chapter discusses various creative approaches and ideas that arose in response to COVID-19, as well as some of the most impactful future trends that emerged as a result. Among the many topics discussed herein are telemedicine, blockchain technology, artificial intelligence, stereolithography, and distance learning.

A New Medical Device to Provide Independent Ventilation to Two Subjects Using a Single Ventilator: Evaluation in Lung-Healthy Pigs

Background

The global crisis situation caused by SARS-CoV-2 has created an explosive demand for ventilators, which cannot be met even in developed countries. Designing a simple and inexpensive device with the ability to increase the number of patients that can be connected to existing ventilators would have a major impact on the number of lives that could be saved. We conducted a study to determine whether two pigs with significant differences in size and weight could be ventilated simultaneously using a single ventilator connected to a new medical device called DuplicARⓇ.

Methods

Six pigs (median weight 12 kg, range 9–25 kg) were connected in pairs to a single ventilator using the new device for 6 hours. Both the ventilator and the device were manipulated throughout the experiment according to the needs of each animal. Tidal volume and positive end-expiratory pressure were individually controlled with the device. Primary and secondary outcome variables were defined to assess ventilation and hemodynamics in all animals throughout the experiment.

Results

Median difference in weight between the animals of each pair was 67% (range: 11–108). All animals could be successfully oxygenated and ventilated for 6 hours through manipulation of the ventilator and the DuplicARⓇ device, despite significant discrepancies in body size and weight. Mean PaCO₂ in arterial blood was 42.1 ± 4.4 mmHg, mean PaO₂ was 162.8 ± 46.8 mmHg, and mean oxygen saturation was 98 ± 1.3%. End-tidal CO₂ values showed no statistically significant difference among subjects of each pair. Mean difference in arterial PaCO₂ measured at the same time in both animals of each pair was 4.8 ± 3 mmHg, reflecting the ability of the device to ventilate each animal according to its particular requirements. Independent management of PEEP was achieved by manipulation of the device controllers.

Conclusion

It is possible to ventilate two lung-healthy animals with a single ventilator according to each one's needs through manipulation of both the ventilator and the DuplicARⓇ device. This gives this device the potential to expand local ventilators surge capacity during disasters or pandemics until emergency supplies can be delivered from central stockpiles.

Delivery system can vary ventilatory parameters across multiple patients from a single source of mechanical ventilation

BACKGROUND

Current limitations in the supply of ventilators during the Covid19 pandemic have limited respiratory support for patients with respiratory failure. Split ventilation allows a single ventilator to be used for more than one patient but is not practicable due to requirements for matched patient settings, risks of cross-contamination, harmful interference between patients and the inability to individualize ventilator support parameters. We hypothesized that a system could be developed to circumvent these limitations.

METHODS AND FINDINGS

A novel delivery system was developed to allow individualized peak inspiratory pressure settings and PEEP using a pressure regulatory valve, developed de novo, and an inline PEEP 'booster'. One-way valves, filters, monitoring ports and wye splitters were assembled in-line to complete the system and achieve the design targets. This system was then tested to see if previously described limitations could be addressed. The system was investigated in mechanical and animal trials (ultimately with a pig and sheep concurrently ventilated from the same ventilator). The system demonstrated the ability to provide ventilation across clinically relevant scenarios including circuit occlusion, unmatched physiology, and a surgical procedure, while allowing significantly different pressures to be safely delivered to each animal for individualized support.

CONCLUSIONS

In settings of limited ventilator availability, systems can be developed to allow increased delivery of ventilator support to patients. This enables more rapid deployment of ventilator capacity under constraints of time, space and financial cost. These systems can be smaller, lighter, more readily stored and more rapidly deployable than ventilators. However, optimizing ventilator support for patients with individualized ventilation parameters will still be dependent upon ease of use and the availability of medical personnel.

Computational simulation to assess patient safety of uncompensated COVID-19 two-patient ventilator sharing using the Pulse Physiology Engine

Background

The COVID-19 pandemic is stretching medical resources internationally, sometimes creating ventilator shortages that complicate clinical and ethical situations. The possibility of needing to ventilate multiple patients with a single ventilator raises patient health and safety concerns in addition to clinical conditions needing treatment. Wherever ventilators are employed, additional tubing and splitting adaptors may be available. Adjustable flow-compensating resistance for differences in lung compliance on individual limbs may not be readily implementable. By exploring a number and range of possible contributing factors using computational simulation without risk of patient harm, this paper attempts to define useful bounds for ventilation parameters when compensatory resistance in limbs of a shared breathing circuit is not possible. This desperate approach to shared ventilation support would be a last resort when alternatives have been exhausted.

Methods

A whole-body computational physiology model (using lumped parameters) was used to simulate each patient being ventilated. The primary model of a single patient with a dedicated ventilator was augmented to model two patients sharing a single ventilator. In addition to lung mechanics or estimation of CO₂ and pH expected for set ventilation parameters (considerations of lung physiology alone), full physiological simulation provides estimates of additional values for oxyhemoglobin saturation, arterial oxygen tension, and other patient parameters. A range of ventilator settings and patient characteristics were simulated for paired patients.

Findings

To be useful for clinicians, attention has been directed to clinically available parameters. These simulations show patient outcome during multi-patient ventilation is most closely correlated to lung compliance, oxygenation index, oxygen saturation index, and end-tidal carbon dioxide of individual patients. The simulated patient outcome metrics were satisfactory when the lung compliance difference between two patients was less than 12 mL/cmH₂O, and the oxygen saturation index difference was less than 2 mmHg.

Interpretation

In resource-limited regions of the world, the COVID-19 pandemic will result in equipment shortages. While single-patient ventilation is preferable, if that option is unavailable and ventilator sharing using limbs without flow resistance compensation is the only available alternative, these simulations provide a conceptual framework and guidelines for clinical patient selection.

A simple method to estimate flow restriction for dual ventilation of dissimilar patients: The BathRC model

BACKGROUND

With large numbers of COVID-19 patients requiring mechanical ventilation and ventilators possibly being in short supply, in extremis two patients may have to share one ventilator. Careful matching of patient ventilation requirements is necessary. However, good matching is difficult to achieve as lung characteristics can have a wide range and may vary over time. Adding flow restriction to the flow path between ventilator and patient gives the opportunity to control the airway pressure and hence flow and volume individually for each patient. This study aimed to create and validate a simple model for calculating required flow restriction.

METHODS AND FINDINGS

We created a simple linear resistance-compliance model, termed the BathRC model, of the ventilator tubing system and lung allowing direct calculation of the relationships between pressures, volumes, and required flow restriction. Experimental measurements were made for parameter determination and validation using a clinical ventilator connected to two test lungs. For validation, differing amounts of restriction were introduced into the ventilator circuit. The BathRC model was able to predict tidal lung volumes with a mean error of 4% (min:1.2%, max:9.3%).

CONCLUSION

We present a simple model validated model that can be used to estimate required flow restriction for dual patient ventilation. The BathRC model is freely available; this tool is provided to demonstrate that flow restriction can be readily estimated. Models and data are available at DOI 10.15125/BATH-00816.