Ventilation Demand Research Articles

Automated Inflating Resuscitator (AIR): Design and Development of a 3D-Printed Ventilator Prototype and Corresponding Simulation Scenario Based on the Management of a Critical COVID-19 Patient.

Recent surges in COVID-19 cases have generated an urgent global demand for ventilators. This demand has led to the development of numerous low-cost ventilation devices, but there has been less emphasis on training health professionals to use these new devices safely. The aim of this technical report is twofold: first, to describe the design and manufacturing process of the automated inflating resuscitator (AIR), a 3D-printed ventilator training device which operates on the principle of pushing a bag valve mask; second, to present a simulation scenario that can be used for training health professionals how to use this and similar, low-cost, 3D-printed ventilators in the context of ventilator shortages caused by COVID-19. To this end, the AIR was designed in an expedient manner in accordance with basic functionality established by the Medicines and Healthcare Products Regulatory Agency (United Kingdom) for provisional clinical use in light of COVID-19.

Demand and supply of invasive and noninvasive ventilators at the peak of the COVID-19 outbreak in Okinawa.

While Okinawa has been facing outbreak of the coronavirus disease 2019 (COVID‐19) pandemic, healthcare collapse should be prevented by sufficient supply of ventilators for caring the rapidly growing number of critically ill patients with COVID‐19. We estimated the number of invasive and noninvasive ventilators that would be required in Okinawa at the peak of the COVID‐19 outbreak based on recent data of COVID‐19 cases in Okinawa and data on the proportion of patients with COVID‐19 in the ICU requiring ventilation. Based on our results using the current supply of all ventilators, demand for ventilators could be prepared for patients with COVID‐19 who would require it and demand for noninvasive ventilators could also be prepared for those with COVID‐19 who would require it. The higher supply over the demand would be achieved by flattening the epidemic curve by implementing public health interventions to delay and suppress the epidemic peak in Okinawa.

On-demand ventilation and energy conservation of industrial exhaust systems based on stochastic modeling

Exhaust ventilation systems have been widely used in factories with multiple heat or pollutant sources. However, conventional “static” designs that fail to consider overlapping terminal ventilation demands result in oversized exhaust systems and high energy consumption. In this work, a novel approach was proposed to calculate dynamic exhaust demand based on stochastic modeling. The developed model could obtain the probability distribution of ventilation demand by adopting the Monte Carlo simulation and determine the optimized designed exhaust rate of the system. A case study showed that the designed exhaust rate of a 20-machine vulcanizing line could be reduced by 45% after the coincidence factor was considered as 0.55. Moreover, an annual energy conservation of 51,465 kWh was possible. The influence of various factors, including exhaust time, cycle time, the number of machines, the number of workers and operating time, was discussed. Findings showed that the coincidence factor was positively proportional to exhaust time but negatively associated with cycle time and the number of machines. In addition, a machine-startup schedule was introduced to optimize the operating schedule, which further reduced the exhaust rate.

Buying Time: Using OMM to Potentially Reduce the Demand for Mechanical Ventilation in Patients With COVID-19.

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) pandemic is causing an increased need for mechanical ventilation for a significant percentage of people who present to the hospital for treatment. This increase in demand could surpass the supply of ventilators and lead to an increase in mortality due to a lack of ventilator vacancies. There is significant evidence that osteopathic manipulative medicine (OMM) can alleviate pulmonary symptoms and aid in quicker recoveries from various respiratory ailments. OMM has the potential to play a significant role in helping reduce a patient's need for mechanical ventilation by delaying the onset of acute respiratory distress syndrome stemming from SARS-Cov2 infections.

Effect of mounting strut and cavitator shape on the ventilation demand for ventilated supercavitation

The present work systematically investigates the effect of cavitator mounting strut and cavitator shape on the ventilation demand to form and sustain a ventilated supercavity under different flow conditions. Three cavitators of different shapes (i.e. 2D cavitators including triangle and disk shape, and 3D cone-shaped cavitator) with the same frontal area are employed for the experiments. The cavitator is connected to a ventilation pipe extended upstream from a mounting strut, referred to as forward-facing model (FFM). The minimal ventilation coefficients to generate (CQf) and to collapse (CQc) a supercavity are measured over a wide range of Froude number (Fr) for each cavitator. Images of overall cavity shapes and topology near closure region as well as the cavity pressure under different experimental conditions are captured simultaneously. The results are compared across different cavitator shapes and the disk cavitator situated on the downstream side of the mount strut, referred to as backward-facing model (BFM). Similar CQf-Fr curves were observed in BFM and FFM-configured disk cavitators. The cone-shaped cavitator requires the least amount of ventilation to generate a supercavity among all different shapes across the range of Fr in our experiments. The CQcof disk FFM is lower than that of its BFM counterpart at small Fr and exceeds the BFM CQcwith further increase of Fr. The cone cavitator has the smallest CQc among all the cavitators across the range of Fr in our experiments. To elucidate the trends of CQc upon changing Fr and cavitator shape, the geometry of supercavity under CQc including its overall shape, the cavity maximum diameter (Dmax) and half length (L1/2) are also investigated. Both Dmax and L1/2 show an increasing then plateauing trend upon increasing Fr across different FFM cavitators despite the smaller values for the 3D cone cavitator. Subsequently, such cavity geometric information and cavity pressure measurements in conjunction with high speed imaging of re-entrant jet are employed to estimate the re-entrant jet momentum under different Fr for disk and cone cavitators. The estimated re-entrant jet momentum shows reasonable match with the ventilation air momentum under CQc in lower Fr for both cavitator cases, with the disk cavitator case yielding significantly stronger re-entrant jet, providing support to the re-entrant jet mechanism governing on the cavity collapse. Our study sheds some light on the cavitator design and ventilation strategy for a supercavitating vehicle in practice.

New Life Breathed Into Ventilator Supply [Coronavirus ventilators

The article looks at how the Covid-19 pandemic has lead to an increase in demand for ventilators by health providers, and at how government and industry have responded. It described the procurement, design, development process and manufacturing of different prototype ventilators, specifically developed to help deal with the consequences of the Covid-19 pandemic.

Can multiple ARDS patients be ventilated with a single ventilator?

Faced with a surge in demand for mechanical ventilators and fewer machines than patients who need them, hospitals are considering ventilating more than 1 patient with a single ventilator (multiplex ventilation). First reported as technically feasible in a test lung model,[1][1] the technique was

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

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

The Optimization of Ventilator Allocation for Maximizing Pandemic Survivability Rates

When the demand for ventilators is expected to exceed the available ventilator capacity, physicians will be forced to decide which patients get a ventilator rig

Descriptive Analysis of Extubations Performed in an Emergency Department-based Intensive Care Unit.

IntroductionExtubation of appropriate patients in the emergency department (ED) may be a strategy to avoid preventable or short-stay intensive care unit (ICU) admissions, and could allow for increased ventilator and ICU bed availability when demand outweighs supply. Extubation is infrequently performed in the ED, and a paucity of outcome data exists. Our objective was to descriptively analyze characteristics and outcomes of patients extubated in an ED-ICU setting.MethodsWe conducted a retrospective observational study at an academic medical center in the United States. Adult ED patients extubated in the ED-ICU from 2015–2019 were retrospectively included and analyzed.ResultsWe identified 202 patients extubated in the ED-ICU; 42% were female and median age was 60.86 years. Locations of endotracheal intubation included the ED (68.3%), outside hospital ED (23.8%), and emergency medical services/prehospital (7.9%). Intubations were performed for airway protection (30.2%), esophagogastroduodenoscopy (27.7%), intoxication/ingestion (17.3%), respiratory failure (13.9%), seizure (7.4%), and other (3.5%). The median interval from ED arrival to extubation was 9.0 hours (interquartile range 6.2–13.6). One patient (0.5%) required unplanned re-intubation within 24 hours of extubation. The attending emergency physician (EP) at the time of extubation was not critical care fellowship trained in the majority (55.9%) of cases. Sixty patients (29.7%) were extubated compassionately; 80% of these died in the ED-ICU, 18.3% were admitted to medical-surgical units, and 1.7% were admitted to intensive care. Of the remaining patients extubated in the ED-ICU (n = 142, 70.3%), zero died in the ED-ICU, 61.3% were admitted to medical-surgical units, 9.9% were admitted to intensive care, and 28.2% were discharged home from the ED-ICU.ConclusionSelect ED patients were safely extubated in an ED-ICU by EPs. Only 7.4% required ICU admission, whereas if ED extubation had not been pursued most or all patients would have required ICU admission. Extubation by EPs of appropriately screened patients may help decrease ICU utilization, including when demand for ventilators or ICU beds is greater than supply. Future research is needed to prospectively study patients appropriate for ED extubation.

Economic Shocks From the Novel COVID-19 Pandemic for Anesthesiologists and Their Practices.

Economic Shocks From the Novel COVID-19 Pandemic for Anesthesiologists and Their Practices.

A strategy of traditional Chinese medicine against COVID-19: linking current basic research and ancient medicine texts

A strategy of integrating Traditional Chinese Medicine (TCM) with Western medicine is proposed for better case management of the coronavirus disease (COVID-19) that is rapidly spreading in the world. We have reviewed the abundant classic TCM literature and from it have linked several key texts to findings from the most updated biomedical research against SARS-CoV-2, including in silico studies of the efficacious compounds in TCM formulae. We have identified three TCM formulae: Yin Qiao San (???), Sang Ju Yin (???), and Xie Bai San (???) as they seem to hold high potentials against SARS-CoV2 in COVID-19 patients. The strategy calls for early administration of proper TCM formulae to decrease the rate of transformation from mild/moderate status into severe/critical status, thereby reducing the demand for ICU facility and ventilators.

Epidemiology and Impact of Healthcare-Associated Infections in Trauma Patients: A National Data Analysis.

Background: Traumatic injuries are a leading cause of death and morbidity. Despite their comprising a small (<5%) segment of all hospitalizations, the length of stay (LOS) is above average; and the cost of care for the more than 20 million trauma inpatients nears $30 billion per year. Adding insult to injury, risk factors for health-care-associated infections (HAI), including invasive devices and comprised integrity, may be particularly pronounced in this population, potentially exacerbating the clinical and economic burden. Our aim was to determine the distribution, determinants, and burden of HAI after traumatic injury using LOS as a surrogate for health-care-related expense. Patients and Methods: This retrospective cohort study used the Trauma Quality Improvement Project (TQIP) database (2013-2016). Patients 16 to 89 years of age were included. Those who developed at least one of the following were counted as cases: Catheter-related central blood stream infection, catheter-related urinary tract infection, ventilator-associated pneumonia, surgical site infection, osteomyelitis, and severe sepsis. Outcomes included the hospital LOS, intensive care unit (ICU) days, and ventilator days. Uni-variable and propensity-matched analyses were conducted to determine differences among patients with and without an HAI. Results: Of 806,066 patients, 5.6% (n = 44,844) developed an HAI. A higher proportion of patients with HAI had co-morbid risk factors of chronicity and history of blood transfusion and rated higher on the Abbreviated Injury Scale than those without HAI. After matching, those with HAI also had significantly longer (3 × ) overall LOS, ICU LOS, and prolonged mechanical ventilation (p < 0.05). Conclusions: This updated epidemiology study of trauma patients showed the HAI burden to be higher than past estimates and disproportionate of all patient estimates. The associated economic burden of a longer ICU stay with a tripling of the LOS and longer mechanical ventilation demands responsible administrative policies and support for infection prevention programs and interventions.

Experimental investigation of critical air entrainment in ventilated cavitating flow for a forward facing model

Ventilated supercavitation is a favorable method for skin friction reduction of underwater bodies, whereby a cavity is generated through artificial injection of air to cover the entire body. In the current study, several experiments are carried out to investigate ventilated supercavity behavior under different flow conditions. A closed-wall water tunnel and air injection system are provided to form ventilated supercavities around a model which was mounted in a forward facing setup. The present research concentrates on the formation and collapse processes of supercavities in order to determine the critical values of air entrainment coefficients which are important parameters for the ventilation demand of a high-speed supercavitating vehicle. Our experiments show that there are critical air entrainment coefficients in which the supercavity length suddenly increases or decreases, due to the change of closure mode between the re-entrant jet regime and twin vortex regime at the rear portion of the supercavity. The results reveal that the formation and collapse air entrainment coefficients vary with Froude number. Moreover, some pressure sensors are positioned in the model and are used to measure the pressure distribution inside the supercavity. The most novelty of our work is to present measurements of the supercavity pressure for a forward facing model, especially at closure region of the supercavity. The pressure measurements show that the pressure increases slightly along the test body surface and is accompanied by a sharp increase at the closure region of the supercavities.

Geometrical optimisation of Transpired Solar Collectors using design of experiments and computational fluid dynamics

Transpired Solar Collectors (TSCs) are simple low maintenance air heating systems which have been widely used for agricultural and industrial applications. In spite of their potential, these systems have not been yet widely employed in residential buildings as they are unable to generate high grade heat for moderate and low ventilation demands. Hence there is an opportunity for optimisation studies in order to enhance the thermal performance of these systems.Optimisation and parametric studies can be costly and time consuming if carried out by physical experiments. CFD models however offer a more flexible and less expensive tool to carry out such studies. This research has aimed to optimise the geometry of the solar absorber plate using a validated CFD model which accounts for a wide range of the key factors affecting TSC performance.A 2nd order polynomial predictive model was developed based on the CFD results with Root Mean Squared Error (RMSE) of 3.8%. The predictive model was used to identify an optimal geometry which delivers a Heat Exchange Effectiveness (HEE) of 0.739. The optimised geometry demonstrated 43% increase in HEE whilst using 28% less material compared to the baseline geometry under the same operating conditions. This geometry can be integrated with other performance enhancement techniques to further improve the thermal performance of TSCs.

Triage protocol for allocation of critical health resources during Covid-19 pandemic and public health emergencies. A narrative review.

Background and aim of the work.Triage during the Covid-19 pandemic can impose difficult allocation decisions when demand for mechanical ventilation or intensive care beds greatly exceeds available resources. Triage criteria should be objective, ethical, transparent, applied equitably and publically disclosed. The aim of this review is to describe the triage tools and process for critical care resources in a pandemic health emergency.Methods.A narrative review was conducted of the literature on five electronic databases, namely PubMed, CINHAL, Web of Science, Cochrane and Embase, searching for studies published from January 2006 to July 2020.Results.The results describe different triage tools. A gold standard of triage does not exist for the adult or paediatric population. Using probability of short-term survival as the sole allocation principle is problematic. In general, each triage protocol should be applied with a specific ethical justification, including transparency, duty to care, duty to steward resources, duty to plan, and distributive justice.Conclusions.Clinical triage decisions based on clinical judgment alone are prone to inconsistent application by triage officers in a pandemic. An ethical framework can inform decision-making and improve accountability. It remains difficult to connect clinical criteria and ethical criteria, because of the models on offer for health services. (www.actabiomedica.it)

Algorithm for Demand Response to Maximize the Penetration of Renewable Energy

Buildings are becoming smarter through the deployment of intelligent and energy-efficient technologies that reduce energy consumption while making buildings easier to manage and operate. Demand for lighting systems, efficient heating, ventilation and air conditioning (HVAC), as well as other types of hardware such as controls and sub-meters, is growing rapidly that needs more attention in terms of the energy efficiency. Moreover, the energy management of micro-generation or poly-generation system has always been very complex. Keeping the balance between demand and production is a challenging task for researchers. This paper investigates a simple yet very effective and intelligent demand response algorithm to mitigate the intermittency problem, providing an uninterrupted power supply to the users. The developed algorithm is fully capable of balancing the consumption and the production by controlling the user pre-defined load patterns that is based on the state of charge (SOC) of the storage system. The algorithm is tested on a microgrid system that consists of different loads, six photovoltaic (PV) solar panels, a small wind turbine system, and a set of lead-acid battery banks. The experimental result shows the maximum use of renewable energy while reducing the peak demand, cost of end-users and low or no carbon emissions. To achieve a significant reduction in energy consumption as well as to keep the balance between production and demand, this algorithm can be implemented for the efficient use of intermittent renewable energy sources.

System design and feasibility of trigeneration systems with hybrid photovoltaic-thermal (PVT) collectors for zero energy office buildings in different climates

Zero or plus energy office buildings must have very high building standards and require highly efficient energy supply systems due to space limitations for renewable installations. Conventional solar cooling systems use photovoltaic electricity or thermal energy to run either a compression-cooling machine or an absorption-cooling machine in order to produce cooling energy during daytime, while they use electricity from the grid for the nightly cooling energy demand. With a hybrid photovoltaic-thermal collector, electricity as well as thermal energy can be produced at the same time. These collectors can produce also cooling energy at nighttime by long-wave radiation exchange with the night sky and convection losses to the ambient air. Such a renewable trigeneration system offers new fields of applications. However, the technical, ecological and economical aspects of such systems are still largely unexplored.In this work, the potential of a PVT system to heat and cool office buildings in three different climate zones is investigated. In the investigated system, PVT collectors act as a heat source and heat sink for a reversible heat pump. Due to the reduced electricity consumption (from the grid) for heat rejection, the overall efficiency and economics improve compared to a conventional solar cooling system using a reversible air-to-water heat pump as heat and cold source.A parametric simulation study was carried out to evaluate the system design with different PVT surface areas and storage tank volumes to optimize the system for three different climate zones and for two different building standards. It is shown such a systems are technically feasible today. With a maximum utilization of PV electricity for heating, ventilation, air conditioning and other electricity demand such as lighting and plug loads, high solar fractions and primary energy savings can be achieved.Annual costs for such a system are comparable to conventional solar thermal and solar electrical cooling systems. Nevertheless, the economic feasibility strongly depends on country specific energy prices and energy policy. However, even in countries without compensation schemes for energy produced by renewables, this system can still be economically viable today. It could be shown, that a specific system dimensioning can be found at each of the investigated locations worldwide for a valuable economic and ecological operation of an office building with PVT technologies in different system designs.

Thermal Diagnostics of Natural Ventilation in Buildings: An Integrated Approach

Diagnostics of natural ventilation in buildings is problematic, as the airflow rate changes considerably over time. One constant average airflow is usually assumed when calculating energy demand for a building, however, such a simplification could be fraught with considerable error. The paper describes a comprehensive methodology for the diagnostics of a natural ventilation system in a building and its practical application. Based on in situ measurements and simulations in two existing buildings (dwelling house and school) in Poland, the real values of the ventilating airflows were analyzed and resulting heat demand was compared with the design values. The pros and cons of various methods for evaluation of natural ventilation are discussed. The real airflow was determined by measurements in a ventilation grille or by a tracer gas concentration decay method. The airtightness of the buildings’ envelope was evaluated based on the fan pressurization test. The last stage entailed computer simulations of air exchange in buildings using CONTAM software. The multizone models of the buildings were calibrated and verified with existing measured data. Measured airflow in a multifamily house was small and substantially deviated from the Polish standard. In case of a school, the air flow rate amounted to an average of 10% of the required value. Calculation of the heat demand for ventilation based on the standard value of the airflow led to a considerable overestimation of this value in relation to the real consumption. In the analyzed cases, the difference was 40% for the school and 30% for the residential building.

Double skin façade with Azolla; ventilation, Indoor Air Quality and Thermal Performance Assessment

Synthesis of architecture and nature is highly reputed as a sustainable approach to overcome dominant built environment challenges, such as indoor air pollution, occupant’s health burden, mechanical ventilation energy consumption as well as the separation between people and nature in urban life.Plants have numerous benefits for indoor spaces, including bioremediation of air contaminants-which promotes the quality of indoor air, drops mechanical ventilation demand, and consequently reduces energy consumption. In this research, a Double Skin Facade (DSF) system is introduced, incorporating Azolla as a natural air purifier in order to absorb occupants’ bio-effluent and also contribute to providing fresh air for indoor spaces. Moreover, the CO2 reduction capacity of Azolla within the DSF as a natural air purifier and its subsequent effects on mechanical ventilation size and the heating/cooling loads is investigated.The challenge for developing the idea of simulating plants activities’ effect through a quantitative method is there are no software or calculating methods that recognize plants as indoor “air purifiers”, therefore, phytoremediation effects on HVAC operation and energy sector have been remained concealed so far. The novelty of this research is attributed to integrating Azolla fern-a hydroponic plant, into building’s components for indoor air bioremediation and establishing a new assessment protocol for integrating greenery’s effect on HVAC loop in which the performance of the DSF incorporating Azolla as a natural air purifier is evaluated through “Indoor Air Quality” and “Ventilation Rate” procedures, which are acknowledged as practical engineering methods for specifying air exchange demand through mechanical equipment.It is observed that within the VR procedure, DSF with Azolla aids in sequestering indoor CO2, while within the IAQ procedure it results in reducing the building’s air exchange demand rate and consequentially, decrease the building’s overall energy consumption.Furthermore, the cooling effect of employing Azolla as natural shading component within a DSF cavity is assessed through applying its latent heat capacity into façade thermal convection/conduction, versus aluminum blinds with the same size and spacings to computationally evaluate the thermal benefits of plants for mitigating cavity/interior spaces overheating. Results are presented demonstrating this effect on “Indoor Sensible Cooling Rates” in 4 different configurations.