Aerosol Release, Distribution and Prevention during Aerosol Therapy: A Simulated Model for Infection Control.

doi:10.21203/rs.3.rs-965054/v1

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Aerosol Release, Distribution and Prevention during Aerosol Therapy: A Simulated Model for Infection Control.

https://doi.org/10.21203/rs.3.rs-965054/v1

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Background: Aerosol therapy is used to deliver medical therapeutics directly to the airways to treat respiratory illnesses. A potential side-effect of this form of treatment is the release of fugitive aerosols into the environment and the exposure of caregivers, other patients, and bystanders to potential viral infections. The aim of this work was to use both flow visualisation and aerosol particle characterisation techniques to study the dispersion, concentrations and size distributions of fugitive aerosols emitted during aerosol therapy delivered via a standard mouthpiece.

Methods: Aerosol therapy was delivered via a nebuliser, aerosol holding chamber and mouthpiece to a spontaneously breathing adult patient model that could mimic the release of patient-derived bioaerosol. A combination of laser and Schlieren imaging were used to non-invasively visualise the release and dispersion of fugitive aerosol particles. Time varying aerosol particle number concentrations and size distributions were measured with optical particle sizers at clinically relevant positions.

Results: The addition of a capture filter to the expiratory port of the mouthpiece significantly reduced the release and spread of fugitive aerosols. Capture filters were effective in curtailing the release of fugitive aerosols of respirable size, ≤ 5 µm in diameter (P ≤ 0.05).

Conclusions: The findings suggest that, where possible, capture filters should be added to the expiratory ports of all aerosol therapy devices to prevent airborne transmission of respiratory illnesses and create safer conditions for healthcare workers and patients.

Critical Care & Emergency Medicine

COVID-19

Aerosol therapy

viral infections

vibrating mesh nebuliser

fugitive emissions

Schlieren imaging

aerosol visualisation.

Since the 2003 outbreak of the Severe Acute Respiratory Syndrome CoronaVirus (SARS-CoV) and subsequent COVID disease in China, there has been an increased focus on understanding the modes of transmission of viral respiratory infections. This focus has intensified since the emergence of the novel coronavirus SARS-CoV-2 from Wuhan, China in late 2019, and the subsequent global pandemic that has ensued.

It has been widely established that viral respiratory infections, such as human avian influenza A (H5N1) [1] and Middle East Respiratory Syndrome (MERS) [2], are transmitted between people through respiratory droplets generated by an infected person coughing, sneezing or speaking [3–5]. If inhaled, these virus carrying aerosols can lead to life threatening illness such as acute respiratory distress syndrome (ARDS) [6, 7]. Aerosol therapy is the primary mode of treatment in such illnesses. The form of aerosol therapy used will vary depending on patient type and the severity of the illness. Whilst highly effective, the treatment type used has the potential to generate additional aerosols by causing the patient to cough or sneeze. These forms of treatment are referred to as Aerosol Generating Procedures (AGPs) and have been known to cause nosocomial infection amongst healthcare workers and others in clinical settings, [8–10]. Thus, in a clinical setting, there is considerable risk of virus transmission, such as SARS-CoV-2, to caregivers, bystanders, and fellow patients. As such, it is imperative that infection control measures are implemented to ensure safe working and treatment environments.

The release and dispersion of fugitive aerosols is much less studied and understood than the delivery of therapeutics to the lungs. Flow visualisation techniques such as Schlieren imaging, Particle Image Velocimetry (PIV), and computational modelling are tools that can provide valuable insights into the behaviour and dispersion distances of fugitive aerosols from the different treatment modalities. The use of such tools has shown that nebuliser air flow, lung function and interface type all significantly impact upon dispersion distance of fugitive emissions [11–14]. However, a limiting factor with these types of tools is the field of view, computational power, and lack of quantitative information on fugitive aerosol particle concentrations and size distributions.

Use of Personal Protective Equipment (PPE) by caregivers is seen as one means of protection against the potential inhalation of infectious fugitive aerosols. However, preventing the release of said emissions at source would be the most effective means of protection. Using Aerodynamic Particle Sizers (APS) McGrath et al. [15] and Mac Giolla Eain et al. [16] quantified the release of fugitive medical aerosols during aerosol therapy. These works found that the addition of capture filters on the expiratory ports of face masks and mouthpieces and use of vibrating mesh nebulisers over jet nebulisers yielded mass concentration levels similar to ambient levels. Instruments such as particle sizers provide qualitative data on aerosol particle concentration, mass, and diameter, however, unless they are positioned in the correct location the data captured may not be particularly relevant and potential aerosol hot spots missed.

To date, there has been no study that has combined the benefits of both flow visualisation with real time aerosol particle characterisation. By combining these measurement techniques, unique insights could be garnered on fugitive aerosol hot spots, dispersion patterns, concentrations, and size distributions. This current study aimed to address this gap in the knowledge. Schlieren and laser imaging in concert with optical particle sizers were used to investigate the spread and characteristics of fugitive aerosols during a simulated aerosol therapy. This study examined whether the addition of capture filter to the aerosol therapy device was an effective means of limiting the release and spread of potentially infectious fugitive aerosols. Based on the findings, a number of recommendations are made to limit the release and spread of fugitive aerosols and improve healthcare worker and patient safety.

A schematic illustration of the experimental setup used to measure the fugitive aerosol levels is presented in Figure 1. An anatomically relevant adult nose-throat model, previously described in [17–19], was connected to an experimental breath actuated aerosol generator and a breathing simulator (BRS2100, Copley Scientific, UK). Simulated normal (Tidal Volume (Vt) = 500 mL, Breath Rate (BR) = 15 breaths per minute (BPM) and Inspiratory: Expiratory (I:E ratio) = 1.0:1.0) [20] and distressed (Vt = 750 mL, BR = 30 BPM and I:E = 1.0:1.0) [21–23] breathing patterns were used in this study. The novel experimental breath actuated aerosol generator mimicked the aerosol generated by a patient on the expiratory flow of the breath only. A saline solution, (0.9 % saline, BBraun, Ireland), was aerosolised in the breath actuated aerosol generator to act as a tracer aerosol [24, 25].

A 2.5 mL dose of 1 mg/mL salbutamol (GlaxoSmithKline Ltd., Ireland) was aerosolised using a vibrating mesh nebuliser (Aerogen Solo, Aerogen Ltd., Ireland) in combination with an aerosol holding chamber (Aerogen Ultra, Aerogen Ltd., Ireland). Salbutamol was chosen as it is a commonly nebulised formulation used in the characterisation of aerosol delivery systems and is specified for use in ISO27427:2013. A standard mouthpiece was used to deliver aerosol from the aerosol holding chamber to the model. A removable bacterial filter (RespirGard II 303, Vyaire Medical Inc., USA) could be placed on the expiratory port of the mouthpiece. Supplemental gas flow rates of 0, 2 and 6 litres per minute (LPM), were considered.

Laser imaging

A 2D slice of the flow field was illuminated by a 2000mW 532nm continuous wave laser expanded through a cylindrical lens. The resulting light sheet was aligned with the sagittal plane of the model. A black sheet cloth provided a uniform dark background to help isolate light scattered by the aerosol from the background. The camera was placed orthogonal to the laser sheet so that the illuminated flow field could be quantified using the PIV method.

Video was recorded using a Canon EOS R5 camera at a resolution of 4096*2160 pixels (DCI 4K) at 29.97 frames per second (FPS). A Canon RF 85mm f/1.2 lens was used; at an aperture of f/1.2 this lens is not diffraction limited and can resolve particles > 4 µm at 4K resolution. This also ensures a uniform out of focus background so that the aerosol can be isolated in the image. PIV allows the quantification of the 2D flow field within the light sheet. The open source PIVLAB library for MATLAB, [26], was used to process the videos and obtain velocity fields.

Schlieren Imaging

Schlieren imaging exploits the local refraction of light by an inhomogeneous medium, such as ambient air. A Z-configuration [27] was employed comprised of two 400 mm diameter parabolic mirrors of focal length 1.8 m. A broadband white light LED (Thorlabs) was used for illumination and the light was focused on to a razor blade. A Canon 5D mk III camera with a EF-100 mm f/2.8 lens was placed downstream of the razor blade and used to record video at 1280 x 720 pixel resolution at 59.94 FPS. Flow features were extracted via sequential frame differencing to enhance the contrast of moving flow, and the Farneback optical flow technique was employed to estimate flow structure advection using MATLAB.

Fugitive Emissions Characterisation

Optical particle sizers (OPS, model 3330, TSI Inc., US) were used to measure aerosol particle number concentrations (PNC) and particle size distributions, between 0.3 µm - 10 µm. Similar to other studies of this type, [15, 28], the OPSs were positioned 0.8 m and 2.2 m from the end of the mouthpiece. Aerosol PNC and size distributions were measured at 5 second intervals for a total of 30 minutes. The 30-minute test consisted of an initial 5-minute period to establish ambient conditions in the test room. The remaining 25 minutes consisted of dose nebulisation, approximately 7 minutes, and aerosol decay post nebulisation. After each test, the room was ventilated and monitored to ensure ambient levels had been re-established.

The use of the breath actuated aerosol generator with the aerosol treatment allowed for a more accurate simulation of the fugitive aerosols generated in a clinically relevant situation. Hence, the data reported represents a more accurate reflection of the fugitive aerosols levels that caregivers, other patients, and bystanders are exposed to. The methods used to measure and characterise the fugitive aerosols in this piece of work could not differentiate between the different types and sources of aerosol, i.e., fugitive medical or patient derived. As such, all the data that is presented and discussed in this piece of work is a combination of both fugitive medical and simulated patient derived aerosols and will be referred to under the blanket term of fugitive aerosol.

Experimental Test Room

The laboratory room in which this study was conducted had dimensions of L = 8.2 m, W = 6.3 m and H = 2.4 m, 124 m³. The mechanical ventilation in the test room was powered off for all testing. The test room had a single occupant who was positioned behind the breathing simulator so as not to affect the distribution of the fugitive aerosols. The air change rate was determined using the tracer gas decay method with CO₂ as the tracer, [29]. An indoor air quality probe (Direct Sense II multi-sensor probe, GrayWolf Sensing Solutions, Shelton, CT, USA) was used to measure the CO₂ levels. The air exchange rate was calculated to be approximately 1.15 /hr.

Statistical Methods

Results are expressed as the mean ± standard deviation of the particle numbers. Paired Student’s t-tests were conducted using the software package Minitab 19.20201.0 (Minitab LLC) to establish if the particle numbers released varied significantly with the different mouthpiece filtration and breathing patterns examined. P-values ≤ 0.05 were considered statistically significant. The experiments were repeated three times independently (n = 3) for each test scenario.

Flow visualisation

Figure 2 shows a collage of representative image frames from the laser imaging video recordings. The colour data has been modified with a look-up-table to invert the image intensity in the dark regions of the image while maintaining a linear response in the rest of the image. This has the advantage of greatly improving the visualisation of the laser illuminated aerosol particles which would otherwise be difficult to discern against the black background. Rows 1 and 2 in Figure 2 show the release of the fugitive aerosols from the unfiltered mouthpiece and rows 3 and 4 show the release of fugitive aerosols from the filtered mouthpiece. The quantity of fugitive aerosol for the unfiltered mouthpiece is significant and was observed to quickly fall towards the floor and out of the field of view of the camera. The addition of the filter to the mouthpiece, rows 3 and 4, greatly reduced the quantity of fugitive aerosol released into the test room. A distressed breathing pattern, characteristic of patients with respiratory difficulties, resulted in a lower quantities of fugitive aerosols released, rows 2 and 4, compared to a normal, quiet breathing pattern.

The results of the Schlieren visualisation are presented in Figure 3. As detailed in the methods section, Schlieren visualisation requires a change in the refractive index, typically in the form of local temperature or species variation. In the case of the filtered mouthpiece tests there was no such change due to the homogenisation of the field by the filter. Similarly, due to the effectiveness of the filter, there is insufficient particles to perform PIV analysis on the data. As such, the images presented in Figure 3 are for the unfiltered mouthpiece only. It is apparent that the aerosol initially follows a very close path to the expiratory port of the mouthpiece. However, this fugitive aerosol plume quickly falls towards the ground, within 0.2 m of the exit of the mouthpiece.

Fugitive Aerosol Emissions

Table 1 presents the time-average particle number concentration for the entire 30-min test duration for each test scenario. The average particle concentration in the test room prior to nebulisation, i.e., ambient conditions, was 110.59 ± 13.75 (91.01 – 128.25) #/cm³. The data in Table 1 confirms the presence of fugitive aerosols in the test room during and post nebulisation. The P-values in Table 1 indicate that the addition of the filter to the mouthpiece made a statistically significant difference to the release and spread of fugitive aerosols, irrespective of breathing pattern and supplemental air flow rate. While there is an increase in the particle numbers above ambient, the recorded values are much closer in approximation to ambient than the unfiltered case.

Table I

Time averaged particle number concentration for the 30-minute test duration. The data in the table shows the effects of mouthpiece filtration, breathing pattern and distance have on fugitive aerosol levels. P-values are included in the table to highlight whether mouthpiece filtration had a statistically significant effect on reducing the levels of fugitive aerosols in the room, with P-values ≤ 0.05 considered significant.

		Average Particle Number Concentration (#/cm³)
		0.8 m			2.2 m
Breathing Pattern	Flow Rate (LPM)	Filtered MP	Unfiltered MP	P-Value	Filtered MP	Unfiltered MP	P-Value
Normal	0	115.17 ± 0.77	154.82 ± 6.28	0.009	115.03 ± 0.66	129.15 ± 2.51	0.014
	2	129.25 ± 3.91	182.61 ± 7.70	0.014	112.70 ± 0.70	148.86 ± 8.23	0.027
	6	146.13 ± 5.13	187.85 ± 3.94	0.001	126.99 ± 3.73	154.72 ± 8.09	0.043
Distressed	0	115.80 ± 1.39	143.90 ± 4.83	0.005	114.58 ± 0.51	129.66 ± 3.40	0.021
	2	121.17 ± 1.41	144.51 ± 5.32	0.025	122.45 ± 1.01	140.27 ± 3.65	0.012
	6	114.83 ± 0.82	147.32 ± 5.95	0.010	115.38 ± 0.36	140.38 ± 3.75	0.018

Table II

Average peak (± standard deviation) particle number concentration above ambient room levels. The data shows the effects of mouthpiece filtration, breathing pattern and distance on fugitive aerosol levels. P-values are included in the table to highlight whether mouthpiece filtration had a statistically significant effect on reducing the levels of fugitive aerosols in the room, with P-values ≤ 0.05 considered significant.
		Peak Particle Number Concentration (#/cm³) above ambient levels
		0.8 m			2.2 m
Breathing Pattern	Flow Rate (LPM)	Filtered MP	Unfiltered MP	P-Value	Filtered MP	Unfiltered MP	P-Value
Normal	0	25.00 ± 3.22	118.85 ± 12.87	0.010	16.06 ± 2.21	67.96 ± 2.34	0.000
	2	42.09 ± 3.71	119.33 ± 11.77	0.004	54.79 ± 4.11	77.71 ± 3.76	0.035
	6	81.27 ± 7.75	154.28 ± 9.15	0.000	57.59 ± 2.18	111.12 ± 13.18	0.017
Distressed	0	31.72 ± 2.76	82.03 ± 12.71	0.027	15.56 ± 2.97	77.50 ± 7.12	0.007
	2	38.42 ± 3.91	86.49 ± 4.32	0.000	31.67 ± 4.40	64.91 ± 4.12	0.001
	6	41.12 ± 7.00	113.01 ± 11.04	0.002	13.00 ± 2.36	78.85 ± 4.44	0.001

Table 2 compares the average peak particle numbers measured for each of the different test scenarios. The data presented in Table 2 is the peak particle numbers above ambient levels (peak value – ambient value). Included in the table are the results of the students t-tests performed to determine whether there was a statistically significant difference in peak particle numbers in the test room with and without a filter on the mouthpiece. Irrespective of distance from the source, supplemental air flow rate through the therapy device and breathing pattern, the addition of a filter to the mouthpiece resulted in a significantly lower level in fugitive aerosols in the test room.

Aerosol Droplet Sizing

Table 3 summarises the average (± standard deviation) particle numbers below a threshold of 5 µm in diameter. This threshold was chosen as it has been documented in the literature that aerosol particles < 5 µm in diameter carry the highest risk of airborne transmission of viral loads and inhalation risk [30–32]. The data in Table 3 highlights the effectiveness of the filter placed on the expiratory port of the mouthpiece in capturing particles below this threshold, with p < 0.05 indicating statistical significance.

Table III

Average (± standard deviation) particle numbers below 5 µm particle diameter threshold for both filtered and unfiltered mouthpieces. The data in the table highlights the effects of mouthpiece filtration, distance, and breathing have on fugitive aerosol levels in the room. P-values are included in the table to highlight whether mouthpiece filtration had a statistically significant effect on reducing the levels of respirable fugitive aerosols in the room, with P-values ≤ 0.05 considered significant.

		PN ≤ 5 µm (#)			PN ≤ 5 µm (#)
		0.8 m			2.2 m
Breathing Pattern	Flow Rate (LPM)	Filtered MP	Unfiltered MP	P-Value	Filtered MP	Unfiltered MP	P-Value
Normal	0	109.67 ± 11.7	150.00 ± 7.02	0.044	93.00 ± 7.00	123.33 ± 10.21	0.036
	2	137.67 ± 8.08	181.67 ± 6.39	0.042	129.33 ± 12.50	163.67 ± 12.01	0.047
	6	272.67 ± 11.15	347.33 ± 11.37	0.033	191.67 ± 5.86	266.33 ± 7.09	0.005
Distressed	0	128.33 ± 8.50	156.00 ± 7.00	0.045	95.33 ± 6.03	121.24 ± 10.00	0.032
	2	125.12 ± 12.53	183.33 ± 8.33	0.002	101.48 ± 6.08	171.33 ± 6.67	0.007
	6	131.00 ± 2.65	334.67 ± 13.20	0.002	122.00 ± 3.61	205.00 ± 8.19	0.006

This study examined the release of fugitive aerosols into the atmosphere during a standard medical aerosol treatment to a spontaneously breathing simulated adult patient. The study provided real-time qualitative and quantitative insights into the dispersion of the fugitive aerosols emitted from expiratory port of a standard mouthpiece used in aerosol therapy.

There are several factors that influence the quantity of fugitive aerosol released, including, but not limited to: device, patient type, and interface. While the concentration and dispersion is affected by the room layout, ventilation, size, temperature and air turbulence [33, 34]. As such, it is necessary to consider these factors when analysing the results of this study.

The addition of the capture filter to the expiratory port of the mouthpiece greatly reduced the release of fugitive aerosols into the atmosphere, with reductions in the peak values ranging from 47.32 – 77.65 % for a normal breathing pattern and 61.33 – 83.55 % for a distressed breathing pattern. Although the reductions were not as significant as those reported in other studies, [15, 16, 35, 36], the images and data highlight the effectiveness of filters in limiting the release and spread of virus carrying fugitive aerosols.

It can be seen from the flow visualisation, Figure 2, that the greatest release of fugitive aerosols was from the unfiltered mouthpiece during simulated normal breathing. The greatest concentration of these fugitive aerosols was within 0.4 m of the end of the mouthpiece and is in agreement with other flow visualisation studies [11, 12, 37]. Moving beyond 0.4 m the concentration of these fugitive aerosols decreases due to the highly chaotic, turbulent flow structure of the fugitive aerosol plume. As a result, the aerosol begins to move more laterally rather than centrally along the midline of the simulated patient. This observation from the flow visualisation data correlates with the data from the particle sizers, Table 1, where the greatest number of particles were detected closer to the expiratory port, 187.85 ± 3.94 #/cm³ at 0.8 m and 154.72 ± 8.02 #/cm³ at 2.2 m. This is particularly relevant to healthcare workers as they are within this 0.4 – 0.8 m range, approximately arm’s length, when treating patients.

The addition of the filter to the mouthpiece greatly reduces the quantity of aerosol released, Figure 2 rows 3 and 4. The exhaled aerosol plume is much smaller and more ordered, similar to a jet in structure. This results in much less lateral spread of the aerosol. However, this much more coherent flow poses a greater risk of long-range aerosol transport longitudinally. This finding corroborates the particle number data presented in Tables 1 and 2, particularly at 0 and 2 LPM supplemental air flow. These findings indicate that although the addition of the filter greatly reduces the quantity of fugitive aerosols, there is a risk that these droplets will deposit on surfaces beyond the 2.2 m range considered in this study and pose a risk of transmission through physical contact, [38]. As such, appropriate precautions should be taken by healthcare workers, other patients, and bystanders.

The breathing pattern of the simulated patient also effected the release and dispersion of fugitive aerosols. The simulated distressed breathing patient generated lower numbers of fugitive aerosols than the normal, healthy breathing pattern, Table 1 & 2. This is also clear from the images presented in the flow visualisation part of this work, Figure 2. Although this result seems counterintuitive, works examining the effects of breathing pattern on aerosol drug delivery have found that delivery efficiency was greater in simulated distressed breathing compared to normal breathing, [23, 39, 40]. The studies attributed the greater aerosol delivery to the increased tidal volume and breath rate of the distressed breathing pattern. Consequently, healthcare workers should be aware that a patient who is not undergoing any breathing difficulties but has a potentially infectious viral infection would be a greater spreader of infection than others.

The addition of a capture filter on the expiratory port had a statistically significant effect on reducing the number of fugitive aerosol particles below the 5 µm critical threshold, p < 0.05. Furthermore, as the additional air flow rate increased the effectiveness of the filter was more apparent. The filters used in this study are rated at 99.9 % bacterial and 99.8 % viral efficiency of 0.3 µm or larger sized particles. Hence, the effectiveness of the filter in capturing particles < 5 µm is unsurprising and should be, where possible, incorporated on the expiratory port of all respiratory therapy devices.

This data presented in this study highlighted a number of means by which healthcare workers, other patients, and bystanders could be exposed to potentially infectious aerosols in a clinical situation. The World Health Organisation (WHO) guidelines for infection prevention and control of acute respiratory infections in healthcare settings recommends that healthcare workers should wear a surgical mask, eye protection and take contact precautions if within 2 m from a potentially infectious patient [41]. However, this work suggests that healthcare workers should wear full airborne protective equipment, N95 mask or equivalent, gown, gloves, goggles, hair covers, and face shield or hood, in any enclosed setting, irrespective of distance, ventilation rate and device filtration. Furthermore, if possible, all aerosol generating procedures or procedures known to generate respiratory events should be performed in negative pressure environments. Environmental cleaning to reduce contact transmission in health care facilities is also necessary.

There are a number of limitations to this study, the in vitro nature constitutes one of its main limitations. The room airflow was switched off during the experiments in order to reveal the maximum distribution of the fugitive aerosol without interference by external airflow. Further work is needed to assess the interaction between, for example, ward and ICU ventilation, on the dispersion of fugitive aerosol. A single aerosol-patient interface and therapy device was used in this study. Further research examining the different types of aerosol therapy-delivery combinations is warranted.

In conclusion, this study presented both qualitative and quantitative data that confirmed the release and dispersion of fugitive aerosols into the environment during a standard nebuliser treatment via a mouthpiece to a spontaneously breathing simulated adult. Our study shows that the addition of a capture filter to the expiratory port of the mouthpiece significantly reduces the release fugitive aerosols. However, the addition of a filter did result in greater long-range dispersion of aerosol particles, which could result in greater potential of contact transmission. A normal, relaxed breathing pattern causes a greater release and spread of fugitive aerosols than a distressed breathing pattern. All healthcare workers should don full protective equipment when entering any setting where aerosol therapy is being performed on potentially infectious patients and rigours decontamination procedures should be implemented at regular intervals. The findings presented in this study should help healthcare organisations to inform policy and best practices for risk mitigation from fugitive aerosols.

ARDS Acute Respiratory Distress Syndrome

APS Aerodynamic Particle Sizers

AGPs Aerosol Generating Procedures

BR Breath Rate

H5N1 Human Avian Influenza A

I:E Inspiratory: Expiratory ratio

MERS Middle East Respiratory Syndrome

OPS Optical Particle Sizers

PIV Particle Image Velocimetry

PNC Particle Number Concentrations

PPE Personal Protective Equipment

SARS-CoV Severe Acute Respiratory Syndrome CoronaVirus

Vt Tidal Volume

WHO World Health Organisation

Ethics Approval and Consent to participate:

Not applicable

Consent for publication

Not applicable

Availability of data and materials

The datasets generated during the current study are available from the corresponding author on reasonable request.

Competing interests

MMGE and RML are employees of Aerogen Limited. KN and RC have no conflict of interest

Funding

This research study was funded by Aerogen Limited. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

Author Contributions

All authors substantially contributed to this article. MMGE, KN, RC and RML were involved in the concept and design of this study. MMGE and KN conducted the study. MMGE and KN carried out the data analysis. All authors were involved in the analysis and interpretation of the data, and in drafting and preparing the manuscript for submission.

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Aerosol Release, Distribution and Prevention during Aerosol Therapy: A Simulated Model for Infection Control.

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Abstract

Figures

Introduction

Methods

Laser imaging

Schlieren Imaging

Fugitive Emissions Characterisation

Experimental Test Room

Statistical Methods

Results

Flow visualisation

Fugitive Aerosol Emissions

Aerosol Droplet Sizing

Discussion

Conclusions

Abbreviations

Declarations

References

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