Negative Pressure Environment Research Articles

Acoustic emission spectrum characteristics of structural coal destruction in negative pressure environment

Abstract The uniaxial compression experiments under a low-pressure environment were performed by using structural coal samples. The frequency domain response characteristics of coal mass failure under loading in a low-pressure environment were acquired by FFT transformation and wavelet packet decomposition. The results show: As the loading stress of coal increases, the AE spectrum becomes more abundant, and the whole AE spectrum shows a left-shift trend. When the gas pressure increases, the acoustic emission signals change from low-frequency high-energy to high-frequency low-energy, the frequency band gradually narrates, and the spectrum changes from complex multi-peak shape to single-peak shape. As stress increases, the proportion of energy in the band 0-4.38 kHz gradually increases, while that in other bands gradually decreases. The energy response to stress changes in the two frequency bands of 2.92-4.38 kHz and 4.38-5.84 kHz is the most obvious. When the pressure changes, the energy in three frequency bands of 2.92-4.38 kHz, 4.38-5.84 kHz, and 7.3-8.76 kHz present an evident response trend with the pressure change, and the response trend (increase) of the latter two is exactly opposite (decrease) to that of the former. This phenomenon indicates that 2.92-4.38 kHz and 4.38-5.84 kHz are the characteristic frequency bands of the coal fracture process. The findings of this research offer crucial foundational data to support the monitoring and early warning of coal and gas outburst hazards.

Performance of an additive-manufactured precooler under high-temperature and negative pressure environment

This paper introduces an original plate-fin precooler designed for potential applications in extreme low-pressure environments. Utilizing additive manufacturing technology, the heat transfer plate thickness is constrained to 2.0 mm, with channel widths inside the plate achieving 0.8 mm. Through experimental methods, this study aims to assess the precooler’s performance and identify critical influencing factors. Experimental results indicate that the hot fluid inlet temperature to the precooler exceeds 1100 K, with static pressures dropping below 30 kPa. Despite these conditions, the precooler demonstrates an impressive pressure recovery coefficient exceeding 97 % and achieves a maximum temperature drop of 731.4 K for the hot fluid. Furthermore, it is observed that the overall performance of the precooler diminishes with increasing mass flow rates of the hot fluid, showing fluctuations of up to 25 % when assessed by the j/f1/3 factor. Additionally, while the hot fluid inlet velocity exceeds 90 m/s, laminar flow predominates during the heat transfer process. Moreover, regardless of whether the cooling fluid experiences a phase change within the precooler, its heat transfer performance show priority than that of the hot fluid. Thus, changes in the mass flow rate of the cooling fluid have minimal impact on the overall precooler performance. Finally, the first-stage heat exchanger plays a critical role in the heat transfer process, accounting for over 2/3 of the total temperature and pressure drop for the hot fluid. This research is expected to contribute to the design of high-efficiency, low-resistance precoolers, particularly those applied for operation under negative pressure conditions.

Study on the foaming behavior of density‐controllable epoxy resin composite foam under negative pressure environment

AbstractThe incomplete decomposition of foaming agent and tedious process during the preparation of epoxy resin composite foam (ERCF) will reduce the mechanical properties and lead to more complex production. Therefore, in this study, a new and simple negative pressure foaming method was designed innovatively to prepare ERCF under negative pressure using strong gas adsorption capacity of inorganically modified calcium silicate (MCS) particles as air carriers instead of foaming agent, and the density and expansion ratio of ERCF could be precisely controlled by adjusting the negative pressure value in a vacuum oven. The results showed that the density of ERCF could reach a very low value of 0.056 g/cm3 at 15 wt% MCS content with decreased negative pressure, but the negative pressure decreases would damage the quality of cells. At the same time, it was found that a rapid rise in the viscosity of the epoxy composite material system under negative pressure of −0.080 MPa owing to the increase in MCS content, when the MCS content was higher than 15 wt%, the MCS dispersion was reduced, leading to a decrease in the quality of the cells. In addition, the ERCF products prepared by the negative pressure foaming method in this study could be easily molded and possessed a better compressive strength among epoxy foams of similar density.

CFD Modelling and Numerical Simulation of the Windage Characteristics of a High-Speed Gearbox Based on Negative Pressure Regulation

Windage power loss plays a leading role in the total power loss of high-speed gears, which seriously affects the transmission efficiency of gear systems and leads to high energy consumption. This paper proposes a negative pressure regulation method to reduce windage power loss. Based on the computational fluid dynamics theory, the flow field distribution and windage power loss in the gearbox under different negative pressure conditions are studied, and the effect of the negative pressure environment and speed on the windage power loss is obtained. In order to further save calculation costs, an optimization algorithm of the BP neural network based on a genetic algorithm is proposed to effectively predict the windage power loss. The results show that the high-speed airflow near the tooth’s surface will produce a large pressure moment, which is the main cause of wind resistance loss. The windage power loss increases with the increase in the negative pressure or speed of the gearbox, but the effect of speed is more obvious. The prediction results of the optimization algorithm are in good agreement with the finite element simulation data and the open literature, which can predict the best parameters for reducing windage power loss.

Design and Verification of Bell-shaped Structure in Negative Pressure Environment for Sound Acquisition of Knee Joint

Design and Verification of Bell-shaped Structure in Negative Pressure Environment for Sound Acquisition of Knee Joint

Gas desorption law of granular coal in negative-pressure environment and calculation of gas loss during negative-pressure sampling

• The gas desorption law at different AEPs and NP conditions was revealed. • The variation law of the diffusion coefficient was obtained by inversion. • The method of gas loss in the process of negative pressure sampling is analyzed. To explore the gas desorption law of granular coal during negative-pressure (NP) slag discharge sampling, atmospheric-pressure (AP) desorption, BP desorption and negative-to-atmospheric pressure (NP-AP) desorption experiments were performed. Based on the experimental results, the variation laws of the gas diffusion coefficient in the NP and NP-AP environments were analyzed through numerical simulation, and the variation laws of gas desorption in the processes of NP desorption and AP desorption were comparatively analyzed. The results show that the gas diffusion coefficient under the NP condition conforms to a power function. At the same adsorption equilibrium pressure (AEP), the initial diffusion coefficient monotonically increases with the rise of NP, that is, the NP environment facilitates gas desorption. At the same desorption environment pressure, the diffusion coefficient is smaller and varies more stably under a higher AEP. Within the same NP sampling time, a higher AEP corresponds to a larger volume of cumulative gas desorption, and a higher NP corresponds to a greater gas loss in the sampling process. This proves that shortening the sampling time can reduce the gas loss at the NP stage and weaken the influence on the desorption at AP. During NP sampling, the logarithmic method is more accurate than the t method in terms of gas loss calculation, its relative error ranging from −56.25% to 16.45%. The relative error is pretty small in the high NP environment and decreases with the passage of the sampling time. Based on the linear relationship between the environmental NP value and the calculation error, the gas loss calculation formulas corrected by error analysis were obtained. The research results can serve as a guideline for further mastering the NP sampling technology.

Innovative dual-function protective scope mask and filtration system for aerosol generating ENT scope procedures.

BackgroundAerosol‐generating procedures (AGPs), such as nasoendoscopy, are considered high‐risk during the COVID‐19 pandemic due to risk of virus aerosol transmission. We aim to evaluate the efficacy of an innovative system in reduction of aerosol contamination.MethodsPilot study involving 15 healthy volunteers performing aerosol‐generating activities with the prototype, compared with and without a standard surgical mask.ResultsWe found an increased frequency of smaller‐sized particle emissions for all four expiratory activities. The particle emission rate with the prototype mask was significantly slower over time for the smallest sized particle (0.3 μm) during breathing, speaking and singing compared with similar activities without the mask (p < .05). We found similar trends for coughing for larger particles but that did not reach statistical significance.ConclusionThe innovation offers good protection against aerosol transmission through the physical barrier of the mask, the negative pressure environment within the mask, and the unit's dual filtration function.Level of evidenceLevel 2b.

Propagation rules of shock waves in confined space under different initial pressure environments

In this paper, an initial pressure adjustable explosion vessel was developed, and the effect of negative pressure, positive pressure (0.2–1.8 atm) different initial ambient pressure on the explosive shock wave generated by the explosion of explosives was studied. The relationships between the specific impulse, shock wave velocity, the amount of explosive gas products and the ambient pressure were analyzed for different initial pressure environments. It was found that: the overpressure of the blast shock wave decreases with the initial ambient pressure of the explosion, and there exists a negative pressure environment with a dramatic pressure decrease near 0.6 atm, defined as the super-sensitive negative pressure Pcr. The propagation velocity of an explosive wave increases with a decrease in the ambient pressure, and the propagation velocity at a pressure of 1.8 atm is four times less than the velocity at a pressure of 0.2 atm. The production of explosive gas products did not change. The greater the initial pressure of the environment where the explosive is located, the smaller the ratio of the gas generated by the explosion to the initial force gas in the explosion vessel is, and the greater the impact on the propagation of shock waves is. The maximum attenuation of the first specific impulse i1 is 72.97% and the maximum attenuation of the second specific impulse i2 is 72.39%. The experiments provide reference data for high-altitude military confrontation, high-altitude weapons and ammunition development, and deep-earth protection engineering.

Experimental and numerical investigations on the condensed combustion products of Mg-based solid fuels

The exploration of condensed combustion products (CCPs) is essential to reveal the ignition, combustion, and infrared radiation mechanisms of Mg-based (Magnesium/polytetrafluoroethylene/Viton) solid fuels that have been considerably employed in the field of aerospace. Systematic experiments and numerical simulations are performed with the physicochemical properties (including morphology, element distribution, phase composition and particle size distribution) and flow field distribution characteristics of CCPs, respectively. The effects of formulation and pressure on the combustion behaviors of pyrotechnic compositions are thoroughly investigated based on thermal analysis measurements, laser ignition, optical diagnosis and CCPs collection. The results demonstrated that the major solid products for all cases are MgF2 agglomerates and MgO smoke oxide particles (SOPs). Increasing the Mg content in the formulation is simultaneously beneficial for the reduction of large agglomerates and SOPs. As the pressure is decreased from 0.1 MPa to 0.02 MPa, the volume weighted mean diameter of CCPs increases significantly due to the decrease in burning rate. The numerical model established in this paper better approximates the realistic combustion process by coupling the heterogeneous condensation reactions, and is adopted to predict the distribution of CCPs in the combustion flow field under different experimental conditions. Numerical results reveal that the MgF2 is mainly distributed in the anaerobic combustion core zone immediately above the burning surface, while MgO is located in the peripheral aerobic combustion diffusion zone. The negative pressure environment has more profound influence on the oxidation reaction of Mg than fluorination reaction. The scientific findings are expected to facilitate the development of more complete combustion and infrared radiation models, while theoretically providing in-depth guidance for the increasing military and civilian application of Mg-based solid fuels.

Effect of Ni on the oxidation behavior of corrosion products that form on low alloy steel exposed to a thin electrolyte layer environment

The oxidation behavior of corrosion products that form on Ni-containing low alloy steel was investigated by electrochemical polarization curves, scanning electron microscopy, electron probe micro-analyzer, X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. The corrosion products were oxidized to Green Rust containing Cl- (Green Rust(Cl-)) and an amorphous substance, which were produced in an ordinary- and negative-pressure environment, respectively. The enrichment of Ni in the corrosion product could inhibit two oxidation reactions of the corrosion product, especially inhibiting the formation of amorphous substances. In addition, oxygen reduction could be also suppressed via the enrichment of Ni.

Numerical Study of Fin-and-Tube Heat Exchanger in Low-Pressure Environment: Air-Side Heat Transfer and Frictional Performance, Entropy Generation Analysis, and Model Development.

Heat transfer and frictional performance at the air-side is predominant for the application and optimization of finned tube heat exchangers. For aerospace engineering, the heat exchanger operates under negative pressure, whereas the general prediction models of convective heat transfer coefficient and pressure penalty for this scenario are rarely reported. In the current study, a numerical model is developed to determine the air-side heat transfer and frictional performance. The influence of air pressure (absolute pressure) is discussed in detail, and the entropy generation considering the effect of heat transfer and pressure drop are analyzed. Furthermore, prediction models of air-side thermal and frictional factors are also developed. The results indicate that both the convective heat transfer coefficient and pressure penalty decrease significantly with decreasing air pressure, and the air-side heat transfer coefficient is decreased by 64.6~73.3% at an air pressure of 25 kPa compared with normal environment pressure. The entropy generation by temperature difference accounts for the highest proportion of the total entropy generation. The prediction correlations of Colburn j-factor and friction factor f show satisfactory accuracy with the absolute mean deviations of 7.48% and 9.42%, respectively. This study can provide a reference for the practical application of fined tube heat exchangers under a negative pressure environment.

Pre-placement of adhesive tape around wound sites can prevent air leakage in negative pressure wound therapy procedures

The introduction of negative pressure wound therapy has revolutionized the management of complicated wounds. However, the maintenance of an effective negative pressure environment is difficult in some instances, such as wounds in close proximity to an intestinal stoma or wounds surrounded by external fixations. We found that adhesive tape adheres more easily to itself than to wet skin or uneven surfaces. Therefore, we placed adhesive tape around surgical wounds prior to covering them with foam and sealing them with more tape. As a result of the strong adhesive force between pieces of tape, this method could provide a better environmental seal, even in situations where space is limited. Pre-placed adhesive tape around the wound site prior to foam placement could provide sufficient adhesion to maintain a continuous negative pressure environment during treatment.

VACUUM-ASSISTED CLOSURE AND MUSCLE FLAP AS AN ALTERNATIVE MODALITY FOR INFECTED WOUND AFTER ORIF OF TIBIAL FRACTURE: CASE REPORT

Background: The blood supply of a bone can be decreased due to the use of an implant, leading to wound-bed bacterial colonization and the development of the SSI. The principle of vacuum-assisted closure (VAC) is to use a negative pressure environment in the wound to promote increased wound healing. The case shows that VAC application and muscle flap therapy provide the definitive healing of infected wounds after ORIF. Case Report: A 45 years-old male presented with a close comminuted proximal third right tibia fracture and tense skin. The fracture was openly reduced and internally fixated with plate fixation and a skin flap on the fracture area. Still, the wound could not be closed due to difficulty covering the wound, so a counter incision was made. After four days, the patient developed necrosis in the post-operation wound and subsequently underwent debridement and muscle flap with VAC application. Discussion: SSI can be treated by applicating of appropriate antibiotic and surgical procedures. In this case, the infection was treated using third-generation cephalosporin antibiotic, debridement, dissection, and re-elevation of gastrocnemius muscle flap covering the exposed plate area in inferior, split skin graft above the muscle flap and VAC above skin graft with 75 mmHg pressure. Conclusion: Debridement with muscle flap and application of VAC in the deep infected wound of open reduction and internal fixation was found to be successful methods in minimizing complications and obtaining an optimal outcome. This finding was associated with accompanying morbidities or a good wound healing process.

Novel Negative Pressure Procedural Tent Reduces Aerosolized Particles in a Simulated Prehospital Setting.

The coronavirus disease 2019 (COVID-19) pandemic has challenged the ability of Emergency Medical Services (EMS) providers to maintain personal safety during the treatment and transport of patients potentially infected. Increased rates of COVID-19 infection in EMS providers after patient care exposure, and notably after performing aerosol-generating procedures (AGPs), have been reported. With an already strained workforce seeing rising call volumes and increased risk for AGP-requiring patient presentations, development of novel devices for the protection of EMS providers is of great importance.Based on the concept of a negative pressure room, the AerosolVE BioDome is designed to encapsulate the patient and contain aerosolized infectious particles produced during AGPs, making the cabin of an EMS vehicle safer for providers. The objective of this study was to determine the efficacy and safety of the tent in mitigating simulated infectious particle spread in varied EMS transport platforms during AGP utilization. Fifteen healthy volunteers were enrolled and distributed amongst three EMS vehicles: a ground ambulance, an aeromedical-configured helicopter, and an aeromedical-configured jet. Sodium chloride particles were used to simulate infectious particles and particle counts were obtained in numerous locations close to the tent and around the patient compartment. Counts near the tent were compared to ambient air with and without use of AGPs (non-rebreather mask, continuous positive airway pressure [CPAP] mask, and high-flow nasal cannula [HFNC]). For all transport platforms, with the tent fan off, the particle generator alone, and with all AGPs produced particle counts inside the tent significantly higher than ambient particle counts (P <.0001). With the tent fan powered on, particle counts near the tent, where EMS providers are expected to be located, showed no significant elevation compared to baseline ambient particle counts during the use of the particle generator alone or with use of any of the AGPs across all transport platforms. Development of devices to improve safety for EMS providers to allow for use of all available therapies to treat patients while reducing risk of communicable respiratory disease transmission is of paramount importance. The AerosolVE BioDome demonstrated efficacy in creating a negative pressure environment and workspace around the patient and provided significant filtration of simulated respiratory droplets, thus making the confined space of transport vehicles potentially safer for EMS personnel.

Air-side flow and heat transfer characteristics research and empirical correlations of wavy fins in negative gauge pressure environment

ABSTRACT When the vehicle cooling system works in negative gauge pressure environment of plateau, it will face the problem of reduced heat transfer performance, which will lead to an increase in vehicle energy consumption. So, there’s important meaning in studying the thermal-hydraulic performance of heat exchangers and optimizing the design of which for negative gauge pressure environments. In this article, experimental study of wavy fin heat exchanger is carried out in negative gauge pressure environment, and then the numerical simulation model is established. The effects of fin size parameters (fin pitch, fin height and fin amplitude) on the temperature field and flow field distribution of wavy fins are studied. Empirical correlations of Colburn j factor and Friction factor f are obtained according to 336 groups of numerical simulation results. The heat transfer coefficient of air side at −44kPa negative pressure is decreased by 34% on average compared with atmospheric pressure, and the friction factor f is increased by 61.5%. The average deviations of correlations for j and f are 2.3% and 2.7%, respectively. The results could be used in engineering practice of design and optimization of wavy fin heat exchangers for vehicle cooling systems operate in plateau environment.

Modeling and Performance Optimization of Louvered Fin Radiators in Negative Gauge Pressure Condition

AbstractThe purpose of this paper is to study the effect of the structural parameters of louvered fin radiators on its thermal‐hydraulic performance, optimize its structural parameters, and improve the performance of louvered fin radiators in negative gauge pressure condition. The thermal calculation model of louvered fin radiator in negative gauge pressure is established. Then, the effects of design variables on thermal‐hydraulic characteristics are investigated. The second generation of nondominated sorting genetic algorithm (NSGA‐II) is applied to optimize the louvered fin heat exchanger in negative gauge pressure environment. Technique for order preference by similarity to an ideal solution is applied to choose the final optimal solution. Numerical simulation of the solution is conducted and the result is compared with literature in order to verify the optimization method. The optimal structural parameters are obtained under constraints. Compared with the original test piece, the heat transfer rate of optimal solution is increased by 7.7%, and total annual cost is reduced by 24.8%. The present paper establishes optimization method of louvered fin radiators in negative gauge pressure condition, the optimization result is superior to the original radiator. The optimization method can be used in the design of radiators operating in negative gauge pressure conditions.

Novel Negative Pressure Helmet Reduces Aerosolized Particles in a Simulated Prehospital Setting.

The coronavirus disease 2019 (COVID-19) pandemic has created challenges in maintaining the safety of prehospital providers caring for patients. Reports have shown increased rates of Emergency Medical Services (EMS) provider infection with COVID-19 after patient care exposure, especially while utilizing aerosol-generating procedures (AGPs). Given the increased risk and rising call volumes for AGP-necessitating complaints, development of novel devices for the protection of EMS clinicians is of great importance.Drawn from the concept of the powered air purifying respirator (PAPR), the AerosolVE helmet creates a personal negative pressure space to contain aerosolized infectious particles produced by patients, making the cabin of an EMS vehicle safer for providers. The helmet was developed initially for use in hospitals and could be of significant use in the prehospital setting. The objective of this study was to determine the efficacy and safety of the helmet in mitigating simulated infectious particle spread in varied EMS transport platforms during AGP utilization. Fifteen healthy volunteers were enrolled and distributed amongst three EMS vehicles: a ground ambulance, a medical helicopter, and a medical jet. Sodium chloride particles were used to simulate infectious particles, and particle counts were obtained in numerous locations close to the helmet and around the patient compartment. Counts near the helmet were compared to ambient air with and without use of AGPs (non-rebreather mask [NRB], continuous positive airway pressure mask [CPAP], and high-flow nasal cannula [HFNC]). Without the helmet fan on, the particle generator alone and with all AGPs produced particle counts inside the helmet significantly higher than ambient particle counts. With the fan on, there was no significant difference in particle counts around the helmet compared to baseline ambient particle counts. Particle counts at the filter exit averaged less than one despite markedly higher particle counts inside the helmet. Given the risk to EMS providers by communicable respiratory diseases, development of devices to improve safety while still enabling use of respiratory therapies is of paramount importance. The AerosolVE helmet demonstrated efficacy in creating a negative pressure environment and provided significant filtration of simulated respiratory droplets, thus making the confined space of transport vehicles potentially safer for EMS personnel.

Development and efficacy testing of a portable negative pressure enclosure for airborne infection containment.

ObjectivesTo overcome the shortage of personal protective equipment and airborne infection isolation rooms (AIIRs) in the COVID‐19 pandemic, a collaborative team of research engineers and clinical physicians worked to build a novel negative pressure environment in the hopes of improving healthcare worker and patient safety. The team then sought to test the device's efficacy in generating and maintaining negative pressure. The goal proved prescient as the US Food and Drug Administration (FDA) later recommended that all barrier devices use negative pressure.MethodsInitially, engineers observed simulations of various aerosol‐ and droplet‐generating procedures using hospital beds and stretchers to determine the optimal working dimensions of the containment device. Several prototypes were made based on these dimensions which were combined with filters and various flow‐generating devices. Then, the airflow generated and the pressure differential within the device during simulated patient care were measured, specifically assessing its ability to create a negative pressure environment consistent with standards published by the Centers for Disease Control and Prevention (CDC).ResultsThe portable fans were unable to generate any airflow and were dropped from further testing. The vacuums tested were all able to generate a negative pressure environment with the magnitude of pressure differential increasing with the vacuum horsepower. Only the 3.5‐horsepower Shop‐Vac, however, generated a −3.0 pascal (Pa) pressure gradient, exceeding the CDC‐recommended minimum of −2.5 Pa for AIIRs.ConclusionA collaborative team of physicians and engineers demonstrated the efficacy of a prototype portable negative pressure environment, surpassing the negative pressure differential recommended by the CDC.

S576 Gastroenterologists’ Utilization of Negative Pressure Rooms During the COVID-19 Pandemic: Results From a US National Survey

Introduction: Since gastrointestinal endoscopy can increase risk of COVID-19 transmission through aerosolization, safety practice guidelines were published. These guidelines recommended performing endoscopic procedures on COVID-19 positive patients in a negative pressure room. In the absence of such room, other enhanced infection control measures were recommended. This study seeks to describe the utilization of negative pressure rooms for endoscopic procedures during the COVID-19 pandemic. Methods: In this IRB-approved multi-center cross-sectional study, we used a snowball sampling approach to disseminate a 42-question survey, pilot-tested for reliability and validity, to gastroenterologists across different geographic locations in the USA. Information on utilization of negative pressure rooms during endoscopies was collected. Fear during endoscopies was assessed using a 1-10 Likert scale. Data was analyzed using Pearson’s chi-squared, Mann-Whitney U, and Wilcoxon rank tests. Results: 69 responses from gastroenterologists at 30 sites (61 academic, 6 community, 1 private practice, and 1 military) were analyzed. Of the 69 responses, 46 (66.7%) reported having a negative pressure room for endoscopic procedures. Gastroenterologists reported performing upper endoscopic procedures on COVID-19 confirmed or suspected patients in a negative pressure environment at the following frequencies: 31 (44.9%) all the time, 5 (7.2%) most of the time, 9 (13%) sometimes, and 1 (1.4%) reported no use of the room. Similar results were found for lower endoscopies: 30 (43.5%) all the time, 5 (7.2%) most of the time, 9 (13%) sometimes, and 2 (2.9%) reported no use of the room. Although 52.2% of respondents reported risk of contracting COVID-19 as their main concern when performing endoscopic procedures on COVID-19 patients, having a negative pressure room did not significantly reduce providers’ fear compared to those without a room (P = 0.661-0.824, compared for first and subsequent procedures, before and after the COVID vaccine). Conclusion: This study shows that only 43.5%-44.9% of the institutions surveyed utilize their negative pressure room all the time for endoscopic procedures concerning COVID-19 patients. Understanding and implementing infection control measures can decrease transmission risk and may decrease gastroenterologists’ fear of infection. Future directions should investigate the standardization of infection control measures in the absence of negative pressure rooms.

Emergency surgery in COVID-19 confirmed patients in hospitals without a negative-pressure operating room

Background: Confirmed coronavirus disease 2019 (COVID-19) patients sometimes require emergency surgery, but protecting healthcare workers and other patients from infection is a high priority. This report describes two cases where surgeries were performed in a hospital without a negative-pressure operating room. Case: Two patients diagnosed with COVID-19 required emergency surgery in a negative-pressure isolation room. Two operating rooms were designated an operating room and an anteroom, and the central air conditioning system was turned off. The disinfection exhaust fan of the operating room was used to create a negative-pressure environment (–1.0 Pa). Conclusions: Performing surgery on COVID-19 patients remains challenging in hospitals not specialized for infection. It is necessary to share experiences between hospitals, and changing the pressure inside the operating room from positive to negative pressure with a simple maneuver is a good option for protection.