Aerosol Leakage Research Articles

Airflow and aerosol transport in the hospital isolation zone based on dynamic scenarios

To contain the leakage of viral aerosols, buffer rooms are usually provided in front of isolation wards. However, dynamic events of door movement and healthcare worker (HCW) walking will result in highly concentrated aerosols intruding into the buffer room from the ward, challenging the control of virus transmission risk. In this work, airflow exchange and bioaerosol particle transport between the negative-pressure isolation ward and the buffer room under dynamic scenarios were studied by transient computational fluid mechanics (CFD) simulation, thereby the fate of particles was divided into invasion stage and decay stage. The effects of ventilation pattern and HCW location on the concentration level and attenuation trend of particles were quantitatively analyzed. The results showed that increasing the HCW walking distance could increase the peak particle concentration within the buffer room by 4.5 % during the invasion stage. The effect of the buffer room ventilation layout on air exchange and particle transport was more pronounced than the HCW stay position. In the decay stage, the two more effective ventilation layouts could decrease the complete clearance time of particles and the particle concentration in the breathing zone by 31 % and 42 %, respectively. To reduce the infection risk, bioaerosol levels need to be reduced both in the buffer room and in the HCW breathing zone.

Measurement of inward leakage of full-face masks in EN and ISO standards: comparison of gas and aerosol test agents.

In Europe, respiratory protective devices must be certified before they can be marketed. Among the parameters of interest, inward leakage (IL) characterizes the tightness between the face seal and the face, to verify that the device is well-designed. European standard EN 13274-1 (2001) and International Organization for Standardization (ISO) standard ISO 16900-1 (2019) specify that IL should be measured using sodium chloride (NaCl) aerosol or sulfur hexafluoride (SF6) gas. For reusable masks made of nonporous materials, both test agents are considered equally acceptable. However, the few studies that have compared IL values measured with various aerosols and gases have come to divergent conclusions. This work then aimed to measure IL with the test agents recommended by the standards to determine whether they are really equivalent. Since krypton (Kr) is an interesting candidate for replacing SF6 in standard tests, IL was assessed with SF6 and Kr simultaneously, and with NaCl aerosol using various calculation methods. Tests were carried out on 5 models of full-face masks donned on a headform connected to a breathing machine simulating 3 sinusoidal breathing rates of various intensities. The respirator fit on the headform was evaluated using a controlled negative pressure method to determine a manikin fit factor. Four scenarios were then tested to represent very poor, bad, good, and excellent fit. Gas concentration was measured using a mass spectrometer, and IL was calculated for SF6 and Kr. A combination of 3 devices allowed the determination of the number-based concentration of particles with diameters between 20 nm and 2 µm, and IL was calculated for each of the 33 channels, as well as using a cumulative number concentration. In addition, to comply with standards, a conversion was carried out to calculate IL using a cumulative mass concentration. The results of this work evidenced that the IL values measured with NaCl were systematically lower than those determined with gases. IL was also shown to vary with particle size, with a maximum value exceeding that calculated with cumulative concentrations (in number or mass). As part of the revision of the standards, protocols for measuring inward leakage should be redefined. On the one hand, acceptability thresholds should be re-evaluated according to the nature of the test agent (gas or aerosol), as it is clear that the 2 options do not give the same results for a given configuration. On the other hand, the aerosol leakage measurement protocol needs to be reworked to enable the measurement of a well-defined, robust, and reproducible inward leakage value.

Experimental study on the leakage behavior of aerosol particles in capillary tubes

The leakage rate of aerosol particles is one of the most important parameters for source term evaluation of containment in severe accidents. In this study, gas leakage characteristics experiments were conducted on capillaries with different inner diameters and tube lengths under different pressure differential conditions. The effects of upstream and downstream pressure differential, capillary tube diameter, tube length, aerosol particle size, whether condensation or not, and release time on aerosol leakage rate were studied. The results show that when the pressure difference between the two ends of the capillary is greater than 0.2 MPa, the leakage rate of the capillary shows a pattern of first increasing and then decreasing with the increase of the pipe diameter; The influence of aerosol particle size on leakage rate mainly affects the inertial deposition effect, which increases with the increase of particle size, leading to a decrease in leakage rate; The condensation effect of steam in capillaries can lead to enhanced effects such as condensate capture, thermophoresis, and diffusion electrophoresis, which have a positive strengthening effect on the retention of aerosol particles.

Experimental study on the retention of aerosol particles through concrete cracks under high Reynolds number flow

In the event of severe accidents in pressurized water reactor (PWR) nuclear power plants, the potential leakage of radioactive aerosols through containment cracks poses a considerable radioactive hazard to the public. Understanding aerosol transport and retention in cracks helps reduce the conservatism and uncertainty of radioactive hazard assessment. Concrete cracks are recognized as a pivotal pathway for the leakage of radioactive aerosols, and several researchers have undertaken experimental investigations concerning the aerosol transport and retention in concrete cracks. However, the majority of these studies have rather low gas flow Reynolds numbers. In this work, an experimental setup is built to study aerosol transport and retention in concrete cracks under high Reynolds number flow. The TiO2 aerosol with a mass median diameter of 1 μm and two concrete crack specimens are used in experiments. The results of gas flow experiments indicate that the Reynolds number is capable of reaching 10547. Combining the flow experimental data and Suzuki's formula, the equivalent heights of these two crack specimens are approximated as 303.67 μm and 231.48 μm. The experimental results indicate a notably high retention rate of aerosols, exceeding 0.8. Furthermore, under high Reynolds number flow, the retention rate varies over a relatively narrow range, with the larger the equivalent height of the crack resulting in a lower retention rate. The experimental results match well with the mechanistic analysis based on inertial deposition theory, demonstrating the rationality of the inertial deposition theory.

COVID-19 in the Clinic: Trial of an Aerosol Containment Mask for Endoscopic Clinic Procedures.

Create an aerosol containment mask (ACM) for common otolaryngologic endoscopic procedures which also provides nanoparticle-level protection to patients. Prospective feasibility study. In-person testing with a novel ACM. The mask was designed in Solidworks and 3-dimensional printed. Measurements were made on 100 consecutive clinic patients who underwent medically necessarily endoscopy, 50 rigid nasal and 50 flexible, by 9 surgeons. Of the 50 patients who underwent rigid nasal endoscopy with the ACM, 0 of 25 patients with the suction off and 0 of 25 patients with the suction on had evidence of leakage of 0.3 μm particles. Of the 50 patients who underwent flexible endoscopy with the ACM, 0 of 25 patients with the suction off and 0 of 25 patients with the suction on had evidence of leakage of 0.3 μm particles. In terms of comfort, 73% of patients found the ACM somewhat or very comfortable without suction, compared to 86% with the suction on. Surgeons were able to visualize all necessary anatomic areas in 98% of procedures. In 97% of procedures, the masks were able to be placed easily. ACM can accommodate rigid nasal and flexible endoscopes and may prevent leakage of patient-generated aerosols, thus avoiding contamination of the room and protecting health care workers from airborne contagions. The level of evidence is 2.

Assessment of risk factors for COVID-19 spread by staff in intensive care units of a multidisciplinary hospital

Objective. To evaluate the risk factors for COVID-19 spreading by personnel of resuscitation units of a multifield hospital.
 Materials and Methods. The study included epidemiological, statistical, and mathematical research methods with retrospective analysis of COVID-19 morbidity and COVID-19 preventive measures in resuscitation units of a multifield hospital.
 Results. The results of the study indicated the highest incidence of COVID-19 among medical personnel in the cardiac surgery and neuroresuscitation units with the highest rates among physicians (66.6 and 45.5 %). The determining risk factors for infection with COVID-19 and other pathogens of acute respiratory diseases among medical personnel were the following: admission of patients in urgent condition to the department without examination results; high load for doctors working with patients, determining the excessive use of personal protective equipment (PPE) by two, four times; violation of rules for PPE removal and utilization conditions, improper storage and contamination of clean PPE, low proportion of PPE use in the interepidemic period; procedures associated with formation of aerosol, airtightness failure during mask ventilation in 24 % of patients that led to leakage of aerosol into the environment, insufficient coverage of medical personnel with preventive vaccination against COVID-19 in some units.
 Conclusions. The high incidence of COVID-19 among medical personnel and workload, violations of PPE usage, and procedures with aerosol formation specific for resuscitation units all these things determine the increased risk of COVID-19 spread by medical staff in resuscitation units.

Minimizing Aerosol Leakage from Facemasks in the COVID-19 Pandemic.

Background: Aerosol therapies with vented facemasks are considered a risk for nosocomial transmission of viruses such as severe acute respiratory syndrome coronavirus 2. The transmission risk can be decreased by minimizing aerosol leakage and filtering the exhaled air. Objective: In this study, we determined which closed facemask designs show the least leakage. Methods: Smoke leakage was quantified during in- and exhalation in a closed system with expiration filter for three infant, six child, and six adult facemasks (three times each mask), using age-appropriate anatomical face models and breathing patterns. To assess leakage, smoke release was recorded and cumulative average pixel intensity (cAPI) was calculated. Results: In the adult group, aircushion edges resulted in less leakage than soft edges (cAPI: 407 ± 250 vs. 774 ± 152) (p = 0.004). The Intersurgical® Economy 5 mask (cAPI: 146 ± 87) also released less smoke than the Intersurgical® Clearlite 5 (cAPI: 748 ± 68) mask with the same size, but different geometry and edge type (p-value <0.05). Moreover, mask size had an effect, as there was a difference between Intersurgical® Economy 4 (cAPI: 708 ± 346) and 5, which have the same geometry but a different size (p-value <0.05). Finally, repositioning masks increased the standard deviations. Mask leakage was not dependent on breathing patterns within the child group. Conclusions: Mask leakage can be minimized by using a closed system with a well-fitting mask that is appropriately positioned. To decrease leakage, and therewith minimize potential viral transmission, selecting a well-fitting mask with an aircushion edge is to be recommended.

CRISPR-Cas and catalytic hairpin assembly technology for target-initiated amplification detection of pancreatic cancer specific tsRNAs.

Transfer RNA-derived small RNAs (tsRNAs) tRF-LeuCAG-002 (ts3011a RNA) is a novel class of non-coding RNAs biomarker for pancreatic cancer (PC). Reverse transcription polymerase chain reaction (RT-qPCR) has been unfit for community hospitals that are short of specialized equipment or laboratory setups. It has not been reported whether isothermal technology can be used for detection, because the tsRNAs have rich modifications and secondary structures compared with other non-coding RNAs. Herein, we have employed a catalytic hairpin assembly (CHA) circuit and clustered regularly interspaced short palindromic repeats (CRISPR) to develop an isothermal and target-initiated amplification method for detecting ts3011a RNA. In the proposed assay, the presence of target tsRNA triggers the CHA circuit that transforms new DNA duplexes to activate collateral cleavage activity of CRISPR-associated proteins (CRISPR-Cas) 12a, achieving cascade signal amplification. This method showed a low detection limit of 88 aM at 37 °C within 2h. Moreover, it was demonstrated for the first time that, this method is less likely to produce aerosol contamination than RT-qPCR by simulating aerosol leakage experiments. This method has good consistency with RT-qPCR in the detection of serum samples and showed great potential for PC-specific tsRNAs point-of-care testing (POCT).

Assessment of Mask Effectiveness to Prevent the Spread of SARS-Cov-2: A Review

Background: The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that causes coronavirus diseases 2019 (COVID-19) is mainly spread person-to-person through droplets and aerosols. It is often recommended that healthcare workers and other people take precautionary measures to reduce their exposure to SARS-CoV-2 by wearing masks. However, the effectiveness of the masks is not well understood at the community level. Methods: To assess the effectiveness of the masks against the SARS-CoV-2 virus, we searched electronic databases (Pubmed, Scopus, and Web of Science) for studies that assessed mask or respirator effectiveness in the prevention of SARS-CoV-2 transmission. Results: The majority of studies reviewed suggested that all types of masks (e.g., N95 respirators, surgical masks, and cloth masks) protect the human respiratory system against airborne viral pathogens, such as SARS-CoV-2. The quality and effectiveness of the masks vary depending on the materials, structures, and methods used for construction. The data shows that both surgical masks and N95 respirators can provide similar protection against airborne respiratory infections, including SARS-CoV-2, for healthcare workers, but due to its better facial fit, N95 is recommended for high-risk environments. However, although masks reduce the spread of SARS-CoV-2, they may not entirely provide proper protection against biologic particles, which are considerably smaller than the accepted most penetrating particle size used in certification tests. Conclusion: While all types of masks have technical pros and cons, wearing them correctly can significantly improve their effectiveness since a complete seal of respiratory particles is unlikely due to side leakage of aerosols of different sizes.

Experimental research on aerosol scrubbing characteristics under steam-air mixture submerged jet condition

The occurrence of severe accidents in nuclear power plants may lead to the leakage of radioactive aerosol. And the scrubbing efficiency of aerosol contained in the air-steam mixture submerged jet is important for assessing the radioactivity in the containment during a severe accident. Several experiments were carried out to analyze the effect of inlet pressure, aerosol diameter, submergence, and steam fraction on the scrubbing efficiency of aerosol in the jet regime. Then, the scrubbing effects of steam and different flow regimes under submerged jet conditions were investigated by comparing the experimental results. The scrubbing efficiency increased with the increase of the aerosol diameter in the air jet regime while the most penetrating region of the aerosol in the steam-air mixture jet regime is 0.2–0.4 μm. When the gas flow characteristic is subcritical flow, as the inlet pressure increases, the scrubbing efficiency increases rapidly. When the critical flow is reached, the inertial effect was the dominant factor in aerosol scrubbing due to the sufficient gas velocity, the scrubbing efficiency under different steam fractions is close to 100%. The scrubbing efficiency increases with the increase of the steam fraction, which may be caused by the increase of the temperature gradient field under subcritical flow conditions. Additionally, the increase the submergence can increase the residence time and improve the scrubbing efficiency. However, due to the decrease of the gas velocity during the gas floating, the scrubbing efficiency in the flow region of the same height is gradually decreasing.

Entrance effect on submicron particles penetration through narrow paths

Deposition of aerosol particles through the micro leak-paths of steel containment has an impact on the radiological consequences under accident conditions. In this work, an experimental facility is set up to study the penetration of submicron particles through a rectangular micro-path under different pressure differences. The flow characteristic height of the path is about 27um obtained by the pure gas leakage test, and the gas leakage through the narrow path is laminar flow when the pressure difference is less than 500 kPa. The effect of pressure difference in the range of 150 kPa to 400 kPa on aerosol particles penetration is investigated in the aerosol leakage tests, which shows that the penetration increases with the increase of pressure difference under laminar flow, and the entrance effect on the particles deposition is studied. A verified semi-empirical correlation based on the balance of lifting and dragging forces is proposed to evaluate the entry loss of aerosol.

Is laparoscopic surgery risk for surgical teams during the coronavirus disease pandemic? An in vitro study with a laser and high-speed camera.

Laparoscopic surgery has been suggested to pose a risk of infection to the surgical team due to aerosol and gas leakage during the coronavirus (COVID-19) pandemic. However, there have been no studies on the risk of gas and aerosol leakage in laparoscopic surgery. We aimed to answer the question "Is the aerosol and gas leakage in laparoscopy is hazardous in terms of coronavirus infection?" with this study. In this study, gas and aerosol leaks were documented by simulating the entry and exit maneuvers from a trocar during laparoscopic surgery using a high-speed camera, fog, and laser in a model representing the abdomen. The maximum gas and aerosol leakage were found during wet gauze extraction from the 10 mm trocar, and its velocity reached 7.5 m/s. The fastest aerosol leakage rate was observed when a 5 mm grasper was extracted from the 5 mm trocar. The results of the subsequent trials were consistent with these values. Higher leakage speeds were observed than the velocity of the exhaled air in a resting person. The surgical crew members, who work very close to the trocars and each other, are at serious risk of infection with COVID-19 which can spread as fast as exhalation speed through trocars. Since there is an evident risk of infection for the surgical crew from laparoscopic surgery of a patient whose intraabdominal fluids are infected with COVID-19, patients must be evaluated elaborately for COVID-19 preoperatively and infected patients should undergo surgery conventionally.

Effectiveness of a novel semi-closed barrier device with a personalized exhaust in cough aerosol simulation according to particle counts and visualization of particles.

Oxygen therapy is an essential treatment for patients with coronavirus disease 2019, although there is a risk of aerosolization of additional viral droplets occurring during this treatment that poses a danger to healthcare professionals. High‐flow oxygen through nasal cannula (HFNC) is a vital treatment bridging low‐flow oxygen therapy with tracheal intubation. Although many barrier devices (including devices without negative pressure in the barrier) have been reported in the literature, few barrier devices are suitable for HFNC and aerosol infection control procedures during HFNC have not yet been established. Hence, we built a single cough simulator model to examine the effectiveness of three protective measures (a semi‐closed barrier device, a personalized exhaust, and surgical masks) administered in isolation as well as in combination using particle counter measurements and laser sheet visualization. We found that the addition of a personalized exhaust to a semi‐closed barrier device reduced aerosol leakage during HFNC without negative pressure. This novel combination may thus reduce aerosol exposure during oxygen therapy, enhance the protection of healthcare workers, and likely reduce nosocomial infection risk.

Surgical mask designed for endoscopic procedures to prevent the diffusion of droplets

Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARSCoV- 2) has become a global pandemic. The human-tohuman transmission of SARS-CoV-2 occurs primarily through droplets, aerosols, and direct contact. Endoscopy is performed at a short physical distance between an endoscopist and patient, which increases the risk of SARS-CoV-2 transmission to the endoscopist through contact with body fluids and exposure to droplets due to vomiting, retching, and coughing during endoscopic procedures (1). Gastrointestinal endoscopic procedures generate aerosols, which mandates the use of appropriate personal protective equipment (PPE) (1,2). To further reduce the risk of viral infection during endoscopy, additional infection protection is needed to assist PPE from not only the side of endoscopists but also the side of patients (3). Various infection prevention devices, such as a reusable plastic cube barrier, have been reported (3); however, we focused on a surgical mask as a simple and inexpensive method (4). Previous studies proposed modified surgical masks with an endoscopic insertion port, which were handmade with an incision for endoscope insertion into commercially available surgical masks (2,4). Although these “handmade” masks may be easily modified, their preparation is burdensome and not sterile. We developed a novel disposal surgical mask with a mask manufacturer that is specifically designed as a droplet prevention device for endoscopic procedures that may be massproduced with uniform quality and easily introduced into endoscopy units. This novel surgical mask has a 10-mm slit in the center for the insertion of an endoscope and two small 6-mm slits for suction on the left and right. The width of the pleats in the center have been widened to easily cut the slits, which allows for cost-effective mass production. Despite its close fit, the narrow slit allows for the easy passage of an endoscope and smooth endoscopic manipulation. Furthermore, the leakage of droplets and aerosols through the slit in the surgical mask is minimized (Fig. 1A-D).

Occupational safety of doxorubicin, cisplatin, paclitaxel, and cremophor-free polymeric micelle formulated paclitaxel during rotational intraperitoneal pressurized aerosol chemotherapy

Objectives: For treating advanced or recurrent cancer with peritoneal carcinomatosis, Pressurized Intraperitoneal Aerosol Chemotherapy has been introduced, which is considered as safe treatment without detectable aerosol leakage. Although we developed a novel prototype of Rotational Intraperitoneal Pressurized Aerosol Chemotherapy (RIPAC) for improving the distribution and depth of penetration of drugs, its occupational safety has not been investigated. This study aimed to investigate potential exposure to health care workers during RIPAC using a hydrophobic agent such as doxorubicin, cisplatin, paclitaxel and cremophor-free polymeric micelle formulated paclitaxel. Methods: As 10% doses for intravenous chemotherapy, doxorubicin of 3 mg, cisplatin of 10 mg, paclitaxel of 30mg, and cremophor-free polymeric micelle formulated paclitaxel of 30 mg were administered with 0.9% NaCl of 50 ml as an aerosol by RIPAC in every three pigs. For preventing aerosol leakage during RIPAC, we used an air-tight trocar and the entire procedure was remotely controlled. Toxic aerosols were eliminated through microparticle filters, and the operating room was equipped with laminar airflow. A sampling of toxic aerosol in the air was performed in breathing zones of operators, anesthesiologists, and scrub nurses, as well as at the entrance of the operating room. Numbers of airborne particles were also assessed to detect potential leakage from the laparoscopic instrument and airborne diffusion. Results: In off-line measurement, we found no detection of leakage during RIPAC using doxorubicin, cisplatin, and cremophor-free polymeric micelle formulated paclitaxel in the air (Limit of detection, LOD, 1.28 ng/ml, 0.772 ng/sample, and 5.68 ng/ml, respectively), while paclitaxel was detected in samples of 75% (LOD, 36.5 ng/sample). In one-line measurement, there was no cumulative risk of leakage of airborne particles during repetitive RIPAC procedures using doxorubicin, cisplatin, and cremophor-free polymeric micelle formulated paclitaxel except increased numbers of airborne particles induced by movements of medical staff. Conclusions: Air contamination of doxorubicin, cisplatin, and cremophor-free polymeric micelle formulated paclitaxel was below the detection limit in the air along with steady levels of numbers of the airborne particles during repetitive RIPAC procedures, suggesting the occupational safety of RIPAC using these three agents. However, paclitaxel may require caution during RIPAC because of a relatively high detection in the air. For treating advanced or recurrent cancer with peritoneal carcinomatosis, Pressurized Intraperitoneal Aerosol Chemotherapy has been introduced, which is considered as safe treatment without detectable aerosol leakage. Although we developed a novel prototype of Rotational Intraperitoneal Pressurized Aerosol Chemotherapy (RIPAC) for improving the distribution and depth of penetration of drugs, its occupational safety has not been investigated. This study aimed to investigate potential exposure to health care workers during RIPAC using a hydrophobic agent such as doxorubicin, cisplatin, paclitaxel and cremophor-free polymeric micelle formulated paclitaxel. As 10% doses for intravenous chemotherapy, doxorubicin of 3 mg, cisplatin of 10 mg, paclitaxel of 30mg, and cremophor-free polymeric micelle formulated paclitaxel of 30 mg were administered with 0.9% NaCl of 50 ml as an aerosol by RIPAC in every three pigs. For preventing aerosol leakage during RIPAC, we used an air-tight trocar and the entire procedure was remotely controlled. Toxic aerosols were eliminated through microparticle filters, and the operating room was equipped with laminar airflow. A sampling of toxic aerosol in the air was performed in breathing zones of operators, anesthesiologists, and scrub nurses, as well as at the entrance of the operating room. Numbers of airborne particles were also assessed to detect potential leakage from the laparoscopic instrument and airborne diffusion. In off-line measurement, we found no detection of leakage during RIPAC using doxorubicin, cisplatin, and cremophor-free polymeric micelle formulated paclitaxel in the air (Limit of detection, LOD, 1.28 ng/ml, 0.772 ng/sample, and 5.68 ng/ml, respectively), while paclitaxel was detected in samples of 75% (LOD, 36.5 ng/sample). In one-line measurement, there was no cumulative risk of leakage of airborne particles during repetitive RIPAC procedures using doxorubicin, cisplatin, and cremophor-free polymeric micelle formulated paclitaxel except increased numbers of airborne particles induced by movements of medical staff. Air contamination of doxorubicin, cisplatin, and cremophor-free polymeric micelle formulated paclitaxel was below the detection limit in the air along with steady levels of numbers of the airborne particles during repetitive RIPAC procedures, suggesting the occupational safety of RIPAC using these three agents. However, paclitaxel may require caution during RIPAC because of a relatively high detection in the air.

COVID-19 in the Clinic: Human Testing of an Aerosol Containment Mask for Endoscopic Clinic Procedures.

ObjectiveTo create an aerosol containment mask (ACM) for common otolaryngologic endoscopic procedures that also provides nanoparticle-level protection to patients.Study DesignProspective feasibility study .SettingIn-person testing with a novel ACM.MethodsThe mask was designed in Solidworks and 3D printed. Measurements were made on 10 healthy volunteers who wore the ACM while reading the Rainbow Passage repeatedly and performing a forced cough or sneeze at 5-second intervals over 1 minute with an endoscope in place.ResultsThere was a large variation in the number of aerosol particles generated among the volunteers. Only the sneeze task showed a significant increase compared with normal breathing in the 0.3-µm particle size when compared with a 1-tailed t test (P = .013). Both the 0.5-µm and 2.5-µm particle sizes showed significant increases for all tasks, while the 2 largest particle sizes, 5 and 10 µm, showed no significant increase (both P < .01). With the suction off, 3 of 30 events (2 sneeze events and 1 cough event) had increases in particle counts, both inside and outside the mask. With the suction on, 2 of 30 events had an increase in particle counts outside the mask without a corresponding increase in particle counts inside the mask. Therefore, these fluctuations in particle counts were determined to be due to random fluctuation in room particle levels.ConclusionACM will accommodate rigid and flexible endoscopes plus instruments and may prevent the leakage of patient-generated aerosols, thus avoiding contamination of the room and protecting health care workers from airborne contagions.Level of evidence2

COVID-19 in the Clinic: Aerosol Containment Mask for Endoscopic Otolaryngologic Clinic Procedures.

ObjectiveTo create an aerosol containment mask (ACM) that contains aerosols during common otolaryngologic endoscopic procedures while protecting patients from environmental aerosols.Study DesignBench testing.SettingMannequin testing.MethodsThe mask was designed in SolidWorks and 3-dimensional printed. Mannequins were fitted with a nebulizer to generate aerosols. Commercial particle counters were used to measure mask performance.ResultsThe ACM has 2 ports on either side for instruments and endoscopes, a port for a filter, and a port that can evacuate aerosols contained within the mask via a standard suction pump. The mask contained aerosols on a mannequin with and without facial hair when the suction was set to 18.5 L/min. Other types of masks demonstrated substantial aerosol leakage under similar conditions. In a subsequent experiment, the ACM contained aerosols generated by a nebulizer up to the saturation of the particle detector without measurable leakage with or without suction.ConclusionThe ACM will accommodate rigid and flexible endoscopes plus instruments and prevent leakage of patient-generated aerosols, thus avoiding contamination of the room and protecting health care workers from airborne contagions.Level of evidence2.

A computational model for predicting changes in infection dynamics due to leakage through N95 respirators

In the absence of fit-testing, leakage of aerosolized pathogens through the gaps between the face and N95 respirators could compromise the effectiveness of the device and increase the risk of infection for the exposed population. To address this issue, we have developed a model to estimate the increase in risk of infection resulting from aerosols leaking through gaps between the face and N95 respirators. The gaps between anthropometric face-geometry and N95 respirators were scanned using computed tomography. The gap profiles were subsequently input into CFD models. The amount of aerosol leakage was predicted by the CFD simulations. Leakage levels were validated using experimental data obtained using manikins. The computed amounts of aerosol transmitted to the respiratory system, with and without leaks, were then linked to a risk-assessment model to predict the infection risk for a sample population. An influenza outbreak in which 50% of the population deployed respirators was considered for risk assessment. Our results showed that the leakage predicted by the CFD model matched the experimental data within about 13%. Depending upon the fit between the headform and the respirator, the inward leakage for the aerosols ranged between 30 and 95%. In addition, the non-fit-tested respirator lowered the infection rate from 97% (for no protection) to between 42 and 80%, but not to the same level as the fit-tested respirators (12%). The CFD-based leakage model, combined with the risk-assessment model, can be useful in optimizing protection strategies for a given population exposed to a pathogenic aerosol.

Comparison of Fit for Sealed and Loose-Fitting Surgical Masks and N95 Filtering Facepiece Respirators.

ObjectivesN95 filtering facepiece respirators (N95 FFRs) and surgical masks are comprised of multiple layers of nonwoven polypropylene. Tight-fitting N95 FFRs are respiratory protective devices (RPDs) designed to efficiently filter aerosols. During the COVID-19 pandemic, health care workers (HCWs) throughout the world continue to face shortages of disposable N95 FFRs. Existing version of widely available FDA cleared loose-fitting surgical masks with straps do not provide reliable protection against aerosols. We tested the faceseal of a modified strapless form-fitting sealed version of surgical mask using quantitative fit testing (QNFT) and compared the performance of this mask with that of N95 FFRs and unmodified loose-fitting surgical masks. MethodsTwenty HCWs participated in the study (10 women; 10 men; age 23–59 years). To create the sealed surgical masks, we removed the straps from loose-fitting surgical masks, made new folds, and used adhesive medical tape to secure the new design. All participants underwent QNFT with a loose-fitting surgical mask, the sealed surgical mask, and an N95 FFR; fit factors were recorded. Each QNFT was performed using a protocol of four exercises: (i) bending over, (ii) talking, (iii) moving head side to side, and (iv) moving head up and down. When the overall fit factor for the sealed surgical mask or N95 FFR was <100, the participant retook the test. Participants scored the breathability and comfort of the sealed surgical mask and N95 FFR on a visual analog scale (VAS) ranging from 0 (unfavorable) to 10 (favorable).ResultsThe median fit factor for the sealed surgical mask (53.8) was significantly higher than that of the loose-fitting surgical mask (3.0) but lower than that of the N95 FFR (177.0) (P < 0.001), equating to significantly lower inward leakage of ambient aerosols (measuring 0.04–0.06 µm) with the sealed surgical mask (geometric mean 1.79%; geometric standard deviation 1.45%; range 0.97–4.03%) than with the loose-fitting surgical mask (29.5%; 2.01%; 25–100.0%) but still higher than with the N95 FFR (0.66%; 1.46%; 0.50–1.97%) (P < 0.001). Sealed surgical masks led to a marked reduction (range 60–98%) in inward leakage of aerosols in all the participants, compared to loose-fitting surgical masks. Among the exercises, talking had a greater effect on reducing overall fit factor for the sealed surgical mask than for the N95 FFR; when talking was excluded, the fit factor for the sealed surgical mask improved significantly (median 53.8 to 81.5; P < 0.001). The sealed surgical mask, when compared with the N95 FFR, offered better reported breathability (median VAS 9 versus 5; P < 0.001) and comfort (9 versus 5; P < 0.001).ConclusionsWidely available loose-fitting surgical masks can be easily modified to achieve faceseal with adhesives. Unlike loose-fitting surgical masks, sealed surgical masks can markedly reduce inward leakage of aerosols and may therefore offer useful levels of respiratory protection during an extreme shortage of N95 FFRs and could benefit HCWs who cannot comply with N95 FFRs due to intolerance. However, because a wide range of surgical masks is commercially available, individual evaluation of such masks is highly recommended before sealed versions are used as RPDs.

Aerosol Exposure During Surgical Tracheotomy in SARS-CoV-2 Positive Patients.

Since December 2019, the novel coronavirus SARS-CoV-2 has been spreading worldwide. Since the main route of infection with SARS-CoV-2 is probably via contact with virus-containing droplets of the exhaled air, any method of securing the airway is of extremely high risk for the health care professionals involved. We evaluated the aerosol exposure to the interventional team during a tracheotomy in a semiquantitative fashion. In addition, we present novel protective measures. To visualize the air movements occurring during a tracheotomy, we used a breathing simulator filled with artificial fog. Normal breathing and coughing were simulated under surgery. The speed of aerosol propagation and particle density in the direct visual field of the surgeon were evaluated. Laminar air flow (LAF) in the OR reduced significantly the aerosol exposure during tracheostomy. Only 4.8 ± 3.4% of the aerosol was in contact with the surgeon. Without LAF, however, the aerosol density in the inspiratory area of the surgeon is 10 times higher (47.9 ± 10.8%, P < 0.01). Coughing through the opened trachea exposed the surgeon within 400 ms with 76.0 ± 8.0% of the aerosol-independent of the function of the LAF. Only when a blocked tube was inserted into the airway, no aerosol leakage could be detected. Coughing and expiration during a surgical tracheotomy expose the surgical team considerably to airway aerosols. This is potentially associated with an increased risk for employees being infected by airborne-transmitted pathogens. Laminar airflow in an operating room leads to a significant reduction in the aerosol exposure of the surgeon and is therefore preferable to a bedside tracheotomy in terms of infection prevention. Ideal protection of medical staff is achieved when the procedure is performed under endotracheal intubation and muscle relaxation.