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      Clear plastic drapes may be effective at limiting aerosolization and droplet spray during extubation: implications for COVID-19

      letter

      , MBCHB, MMed, MHSC, , MD, FRCA, , BMBS, BMedSci, FRCA

      Canadian Journal of Anaesthesia

      Springer International Publishing

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          Abstract

          To the Editor, Health care providers (HCPs) performing aerosol-generating medical procedures (AGMP) in patients with the disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), also known as coronavirus disease (COVID-19), are considered to be at higher risk for contracting the disease.1 Reports on the airborne transmission of SARS-CoV-2 have resulted in concerns over increased risk for infection, especially with global shortages of personal protection equipment (PPE) needed for droplet precautions.2 Contamination of surfaces and personnel with virus-loaded droplets may occur during high-risk AGMP, such as intubation and extubation. A recent report recommended the use of gauze around the patient’s mouth as a method for reducing the aerosolization of the virus.1 Our group performed a series of experiments assessing whether clear plastic drapes were effective in containing aerosolization during extubation. These experiments did not require institutional research ethics approval. All experiments utilized Glo-germ™ (Glo Germ Company, Moab, UT, USA), a fluorescent resin powder with particle sizes between 1 and 5 µm (SARS-COV-2 is 0.07–1.2 µm), with ultraviolet light detection in a darkened operating room. A pediatric mannequin (Eletripod ET/J10 Tracheal Intubation model, Tuqi, China) was used. Simulated secretions (0.5 mL of Glo-germ) were applied to the oropharynx and the mid-trachea of the mannequin. A cough was simulated using a calibrated medical air gun connected to the distal trachea, fired over 0.4 sec, delivering cough peak expiratory flow rates (CPEFR) of 150–180 L·min−1 outward from the trachea. The normal CPEFR ranges from 87 L·min−1 in children under one year to 728 L·min−1 in some adults; a CPEFR < 175 L·min−1 is predictive of failure to extubate in adults.3–5 Between experiments, the mannequin was cleaned with alcohol, soap, and water. All experiments were video recorded (240 fps) using a combination of GoPro Hero 6 (GoPro Inc, San Mateo, CA, USA), iPhone X, X Max, and XR (Apple Inc, Cupertino, CA, USA). In the first series of experiments (Exp), we simulated a cough during extubation of the mannequin both without (Exp 1A) and with (Exp 1B) a single clear plastic drape applied over the head and endotracheal tube. We then repeated the same extubation cough sequence in a second series of experiments (Exp 2) using a modified three-layer plastic drape configuration. The first layer was placed under the head of the mannequin to protect the operating table and linen. The second torso-drape layer was applied from the neck down and over the chest, preventing contamination of the upper torso. The final over-head top drape was a clear plastic drape with a sticky edge that was secured at the mid-sternum level. It was draped over the patient’s head to prevent contamination of the surrounding surfaces, including the HCPs. After the cough was complete, the top two drapes were rolled away together toward the patient’s legs to contain and remove the contaminant, and the third drape was removed afterwards. A cough without any plastic drapes applied (Exp 1A) resulted in a wide distribution of droplets contaminating the surrounding areas (Figure A and eVideo in the Electronic Supplementary Material [ESM]).1 The use of a single clear plastic drape (Exp 1B) restricted the aerosolization and droplet spraying of the particles, but using the three-drape technique (Exp 2) significantly reduced contamination of the immediate area surrounding the patient (Figure B; eVideo in the ESM). An area of significant contamination, a “hot-zone”, was noted on the drape covering the bed beneath the mannequin head (Figure C). The patient’s face and head were also contaminated (Figure C). Nevertheless, we were able to successfully remove these drapes (by rolling them up) without further contamination of the area or the HCP. This was evidenced by the lack of fluorescent particles on visual inspection. Figure The distribution of particles following the use of a three-layered clear plastic drape configuration for extubation with a simulated cough. A) In experiment (Exp) 1A described in the text, coughing during extubation contaminated the airspace around the patient, including the torso, face, head, and bed. B) In Exp 2, a three-panel clear plastic drape was used: first layer placed under the head of the mannequin to protect the operating table and linen; second torso-drape layer applied from the neck down and over the chest, preventing contamination of the upper torso; third over-head top drape with a sticky edge secured at the mid-sternum level. The clear plastic drapes restrict contamination (white fluorescent particles) to the areas between the top clear plastic and the bottom clear plastic drape, as seen in the view from the patient’s head under the third drape covering the face. C) Following removal of the top clear plastic drape and torso clear plastic drape in Exp 2, the contamination is restricted to the area previously under the top clear plastic drape. There is no contamination of the area previously covered by the torso clear plastic drape. Our series of experiments (each performed once) were proof-of-concept on the patterns of aerosolization and droplet sprays during extubation and the impact of clear drapes. We showed that the use of low-cost barriers (clear plastic drapes) was able to significantly limit aerosolization and droplet spray. Protection of frontline HCPs is paramount. Nevertheless, PPE is a limited resource and often requires providers to be adaptive and resourceful in a crisis. The inexpensive and simple method of using clear drapes during extubation (and possibly intubation) of COVID-19 patients may be considered by frontline HCPs and infection control specialists as an additional precaution. Modifications of the clear plastics can be adapted for surgical procedures that may be AGMPs. Limitations of this work include its low-fidelity design and use of a larger particle (Glo-Germ) that may not reflect true spread of a virus like SARS-CoV-2. It is particularly important that HCPs take care not to generate further aerosols when removing the drapes; and we recommend using the three-panel draping as opposed to the single-drape technique. Further studies will be needed to further refine this model and its findings. Electronic supplementary material Below is the link to the electronic supplementary material. Supplementary material 1 The use of a single clear plastic drape in minimizing aerosolization, droplet spraying, and room contamination. This concept has been reported elsewhere (https://twitter.com/innov8doc/status/1240455223929458696) (MP4 12690 kb)

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          Most cited references 5

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          Aerosol and Surface Stability of SARS-CoV-2 as Compared with SARS-CoV-1

          To the Editor: A novel human coronavirus that is now named severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) (formerly called HCoV-19) emerged in Wuhan, China, in late 2019 and is now causing a pandemic. 1 We analyzed the aerosol and surface stability of SARS-CoV-2 and compared it with SARS-CoV-1, the most closely related human coronavirus. 2 We evaluated the stability of SARS-CoV-2 and SARS-CoV-1 in aerosols and on various surfaces and estimated their decay rates using a Bayesian regression model (see the Methods section in the Supplementary Appendix, available with the full text of this letter at NEJM.org). SARS-CoV-2 nCoV-WA1-2020 (MN985325.1) and SARS-CoV-1 Tor2 (AY274119.3) were the strains used. Aerosols (<5 μm) containing SARS-CoV-2 (105.25 50% tissue-culture infectious dose [TCID50] per milliliter) or SARS-CoV-1 (106.75-7.00 TCID50 per milliliter) were generated with the use of a three-jet Collison nebulizer and fed into a Goldberg drum to create an aerosolized environment. The inoculum resulted in cycle-threshold values between 20 and 22, similar to those observed in samples obtained from the upper and lower respiratory tract in humans. Our data consisted of 10 experimental conditions involving two viruses (SARS-CoV-2 and SARS-CoV-1) in five environmental conditions (aerosols, plastic, stainless steel, copper, and cardboard). All experimental measurements are reported as means across three replicates. SARS-CoV-2 remained viable in aerosols throughout the duration of our experiment (3 hours), with a reduction in infectious titer from 103.5 to 102.7 TCID50 per liter of air. This reduction was similar to that observed with SARS-CoV-1, from 104.3 to 103.5 TCID50 per milliliter (Figure 1A). SARS-CoV-2 was more stable on plastic and stainless steel than on copper and cardboard, and viable virus was detected up to 72 hours after application to these surfaces (Figure 1A), although the virus titer was greatly reduced (from 103.7 to 100.6 TCID50 per milliliter of medium after 72 hours on plastic and from 103.7 to 100.6 TCID50 per milliliter after 48 hours on stainless steel). The stability kinetics of SARS-CoV-1 were similar (from 103.4 to 100.7 TCID50 per milliliter after 72 hours on plastic and from 103.6 to 100.6 TCID50 per milliliter after 48 hours on stainless steel). On copper, no viable SARS-CoV-2 was measured after 4 hours and no viable SARS-CoV-1 was measured after 8 hours. On cardboard, no viable SARS-CoV-2 was measured after 24 hours and no viable SARS-CoV-1 was measured after 8 hours (Figure 1A). Both viruses had an exponential decay in virus titer across all experimental conditions, as indicated by a linear decrease in the log10TCID50 per liter of air or milliliter of medium over time (Figure 1B). The half-lives of SARS-CoV-2 and SARS-CoV-1 were similar in aerosols, with median estimates of approximately 1.1 to 1.2 hours and 95% credible intervals of 0.64 to 2.64 for SARS-CoV-2 and 0.78 to 2.43 for SARS-CoV-1 (Figure 1C, and Table S1 in the Supplementary Appendix). The half-lives of the two viruses were also similar on copper. On cardboard, the half-life of SARS-CoV-2 was longer than that of SARS-CoV-1. The longest viability of both viruses was on stainless steel and plastic; the estimated median half-life of SARS-CoV-2 was approximately 5.6 hours on stainless steel and 6.8 hours on plastic (Figure 1C). Estimated differences in the half-lives of the two viruses were small except for those on cardboard (Figure 1C). Individual replicate data were noticeably “noisier” (i.e., there was more variation in the experiment, resulting in a larger standard error) for cardboard than for other surfaces (Fig. S1 through S5), so we advise caution in interpreting this result. We found that the stability of SARS-CoV-2 was similar to that of SARS-CoV-1 under the experimental circumstances tested. This indicates that differences in the epidemiologic characteristics of these viruses probably arise from other factors, including high viral loads in the upper respiratory tract and the potential for persons infected with SARS-CoV-2 to shed and transmit the virus while asymptomatic. 3,4 Our results indicate that aerosol and fomite transmission of SARS-CoV-2 is plausible, since the virus can remain viable and infectious in aerosols for hours and on surfaces up to days (depending on the inoculum shed). These findings echo those with SARS-CoV-1, in which these forms of transmission were associated with nosocomial spread and super-spreading events, 5 and they provide information for pandemic mitigation efforts.
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            Intubation and Ventilation amid the COVID-19 Outbreak

            The COVID-19 outbreak has led to 80,409 diagnosed cases and 3,012 deaths in mainland China based on the data released on March 4, 2020. Approximately 3.2% of patients with COVID-19 required intubation and invasive ventilation at some point in the disease course. Providing best practices regarding intubation and ventilation for an overwhelming number of patients with COVID-19 amid an enhanced risk of cross-infection is a daunting undertaking. The authors presented the experience of caring for the critically ill patients with COVID-19 in Wuhan. It is extremely important to follow strict self-protection precautions. Timely, but not premature, intubation is crucial to counter a progressively enlarging oxygen debt despite high-flow oxygen therapy and bilevel positive airway pressure ventilation. Thorough preparation, satisfactory preoxygenation, modified rapid sequence induction, and rapid intubation using a video laryngoscope are widely used intubation strategies in Wuhan. Lung-protective ventilation, prone position ventilation, and adequate sedation and analgesia are essential components of ventilation management.
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              The impact of high-flow nasal cannula (HFNC) on coughing distance: implications on its use during the novel coronavirus disease outbreak

              To the Editor, Novel coronavirus disease (COVID-19) caused by severe acute respiratory syndrome coronavirus-2 threatens healthcare resources throughout the world. This is particularly true for the patients who develop moderate to severe respiratory failure and require oxygen supplementation devices such as high-flow nasal cannula (HFNC).1 The HFNC uses humidification to allow the delivery of up to 100% oxygen at flow rates of up to 60 L·min−1; however, there is a concern this may aerosolize respiratory tract pathogens. The World Health Organization (WHO) released interim guidance on the management of severe respiratory infection when COVID-19 is suspected.2 Using evidence from several recently published studies,2,3 WHO guidance proffers that HFNC do not create wide-spread dispersion of exhaled air and therefore should be associated with low risk of transmission of respiratory viruses. This document also recommends wearing a standard medical face mask if the healthcare worker is within 2 m of the patient and there is a physical bed separation of at least 1 m. We carried out an experiment to simulate a patient coughing while using HFNC to assess the maximum distance of droplet dispersion. Formal ethics approval was waived by the Office of Human Research Protection Programme, National Healthcare Group, Singapore. The authors (n = 5), with no history of lung disease, participated. All gargled 10 mL of diluted red then blue food dye. They were then seated with their mouths approximately 1.30 m from the floor, inhaled to vital capacity, and coughed with an open mouth. Each participant coughed twice and the furthest distance that a visible food dye droplet travelled on the ground was measured. The process was repeated while wearing a well-fitting HFNC (2004F7015 High/Low Blender, Bio-Med USA and Optiflo, Fisher Paykel Healthcare New Zealand) at 60 L·min−1 flow. We showed that in these healthy volunteers, cough-generated droplets spread to a mean (standard deviation) distance of 2.48 (1.03) m at baseline and 2.91 (1.09) m with HFNC. A maximum cough distance of 4.50 m was reported when using HFNC (Table). Table Droplet dispersion distances during simulated coughing Participant Distance without HFNC (m) Distance with HFNC (m) Difference in distance (m) Female, 159 cm, 46 kg 1.03 1.53 0.50 Male, 171 cm, 76 kg 2.33 3.17 0.84 Male, 171 cm, 79 kg 3.90 4.50 0.60 Male, 170 cm, 70 kg 2.43 2.41 − 0.02 Female, 161 cm, 71 kg 2.73 2.92 0.19 Mean (SD) values 2.48 (1.03) 2.91 (1.09) 0.42 (0.34) HFNC = high-flow nasal cannula; SD = standard deviation Hui et al. 3 used a simulator model and a smoke-laser illumination technique to investigate the dispersion of droplets amplified by HFNC. They showed that when HFNC flow rates were increased from 10–60 L·min−1, non-cough exhaled air distances (in the forward direction) increased from 6.5 to 17.2 cm, and up to 62 cm (in the lateral direction). It is uncertain if such short distances are accurate in patients who are coughing. Leung et al.4 found no evidence of increased surrounding surface contamination when using HFNC in patients with gram negative bacterial pneumonia. Nevertheless, extrapolating findings from patients with bacterial pneumonia to those with viral pneumonia may not be rational. In our study, four of the five volunteers’ cough droplets travelled further than the WHO-recommended 2 m safe exclusion zone. Overall, the distance of droplet dispersion from coughing increased by an average of 0.42 m with HFNC. Using the other studies3,4 as a guide, the safest way to use HFNC during the current COVID-19 outbreak is to embrace the potential of nosocomial airborne transmission and ensure HFNC devices are at least used in single occupancy rooms or negative pressure airborne isolation rooms5 when possible. Healthcare workers caring for those using HFNC should be wearing full airborne personal protective equipment (i.e., N95 mask or equivalent, gown, gloves, goggles, hair covers, and face shield or hoods).
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                Author and article information

                Contributors
                clyde.matava@sickkids.ca
                Journal
                Can J Anaesth
                Can J Anaesth
                Canadian Journal of Anaesthesia
                Springer International Publishing (Cham )
                0832-610X
                1496-8975
                3 April 2020
                : 1-3
                Affiliations
                GRID grid.17063.33, ISNI 0000 0001 2157 2938, Department of Anesthesia and Pain Medicine, Department of Anesthesia, Faculty of Medicine, The Hospital for Sick Children, , University of Toronto, ; Toronto, ON Canada
                Article
                1649
                10.1007/s12630-020-01649-w
                7124129
                32246431
                5e2f6fde-ea55-422f-b197-fc6fb96f13fc
                © Canadian Anesthesiologists' Society 2020

                This article is made available via the PMC Open Access Subset for unrestricted research re-use and secondary analysis in any form or by any means with acknowledgement of the original source. These permissions are granted for the duration of the World Health Organization (WHO) declaration of COVID-19 as a global pandemic.

                Categories
                Correspondence

                Anesthesiology & Pain management

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