Bronchoscopy safety precautions for diagnosing COVID‐19 associated pulmonary aspergillosis—A simulation study

With the outbreak of coronavirus disease 2019 (COVID‐19), clinicians have used personal protective equipment to avoid transmission of severe acute respiratory syndrome coronavirus 2. However, they still face occupational risk of infection, when treating COVID‐19 patients. This may be highest during invasive diagnostic procedures releasing aerosols and droplets. Thereby, the use of diagnostic procedures for Covid‐19 associated aspergillosis may be delayed or impeded, as use of bronchoscopy has been discouraged. This leads to avoidance of a crucial procedure for diagnosing invasive aspergillosis. We intent to visualise aerosol and droplet spread and surface contamination during bronchoscopy and address which measures can avoid exposure of health‐care workers.


| INTRODUC TI ON
Health-care workers (HCWs) are at increased occupational risk of infection, when managing coronavirus disease 2019 (COVID-19) patients. 1 Such risk may be highest during invasive diagnostic procedures releasing aerosols and droplets. 2 Use of bronchoscopy and bronchoalveolar lavage (BAL) has thus been discouraged in patients with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. In intubated patients, tracheal aspirates and other respiratory specimens should be considered instead. Many mechanically ventilated COVID-19 patients suffer from acute respiratory distress syndrome (ARDS), and standard treatment comprises positive pressure-controlled ventilation with application of positive end-expiratory pressure (PEEP), respiratory gas humidification and temperature control. During intensive care for COVID-19 patients, however, emergency bronchoscopy may be required. Massive haemoptysis (>200 mL/24 h), foreign body removal, airway obstruction or atelectasis due to mucus plug are immediate threats to patient life. Any of these emergencies can force physicians into greater risk of exposure to SARS-CoV-2, 3 and to open the closed respiratory circuit. Aerosol and droplets from tubes and mounts may harbour SARS-CoV-2 which will then be released into ambient air. To diagnose secondary infection, and especially COVID-19 associated pulmonary aspergillosis (CAPA), lower respiratory samples obtained by BAL are the samples of choice. 4,5 However, due to its restricted use, non-validated tests have been used from upper respiratory tract specimen. 6 By avoiding the standard diagnostics, secondary infections could be missed or diagnosed with delay. Furthermore, localised infections such as tracheobronchitis cannot be visualised and the possibility of obtaining biopsies or direct samples is missed. 7 To endeavour this, we simulated bronchoscopy in an intubated patient and visualised aerosol and droplet release. We discuss measures to avoid exposure of health-care workers.

| Bronchoscopy simulation model
We created a simulation model using a modified resuscitation simulator (Laerdal Resusci Anne simulator). The simulator was intubated Condensed water in the closed circuit was simulated by applying 1 mL fluorescent solution for verification of hand disinfection procedures (Schülke optics, Schülke & Mayr GmbH) into the smoothbore catheter mount. All simulations were performed at room temperature. We used an endoscopy telescopic drape (SteriVision ™ Plus Telescopic drape, merosystems ™ ) and cut a small hole into the distal end (1 × 1 cm, fitting to the tube mount). We sealed the proximal end of the cover with a tie-wrap close to the bronchoscope handle.
An Ambu ® aScope ™ 4 Broncho Large (5.8/2.8) single use bronchoscope (Bad Nauheim, Germany) was used. Video recording from different angles was done with two Apple ™ iPhone 11 Pro in parallel (Cupertino, CA, USA). For every video take the dressing at the model's chest and gloves were changed to avoid contamination and fluorescent training solution was re-applied within the nebuliser and smoothbore catheter mount. We used the preinstalled slow-motion camera mode with 240 fps. Video editing (cutting only, adding fade-in and outs and arrows; no postproduction increase of colours or contrast) was done with Wondershare Filmora 9 (Wondershare Software Co., Ltd). No IRB approval was needed for this educational study.

| Preparation and equipment
Apply single use bronchoscopes to eliminate requirement to clean scopes and risk of cross-contamination, and to increase portability and out-of-hours availability. Prepare sample tubes including adequate labelling and fill in laboratory and transport forms and saline in syringes From here, all procedures should be performed using sterile material (covers, scissors and gloves). Insert the bronchoscope into the sterile cover and seal the cover with a tie-wrap close to its handle at the proximal end. Cut a hole-corresponding to the diameter of the endotracheal tube mount-into the tip of a sterile cover used for ultrasound transducers or endoscopic cameras. Insert the endotracheal tube mount into the sterile cover and fix it with adhesive tape, while the bronchoscope rests in the sterile cover ( Figure 4A). Apply suction to the bronchoscope.

| RE SULTS -S IMUL ATION MODEL
Upon opening the closed respiratory circuit, the following critical situations appear: Opening the tube mount releases a spray of droplets to the patient chest and abdomen as well as an aerosol ( Figure 1A, 1B).
The direction of the flip top cap being opened, and the fingers of the examiner determine the direction of the aerosol (Video 1, Video S1) (Critical phase 1). The sudden release of pressure by opening the closed respiratory system and the continued operation of the ventilator lead to distribution of aerosol and droplets within the room. Inserting the bronchoscope causes turbulence and deflects droplets into multiple directions (Video 2, Figure 1C, 1D, Figure S2) (Critical phase 2).
Removal of the bronchoscope and closure of the flip top cap causes deflection of droplets (Video 3, Video S2, Figure 2A) (Critical phase 3).
Depending on the trajectory of the aerosol and droplets profound, surface contamination can be detected at the patient's chest as well as on the examiner's fingers (Figure 3). Installation of a simple cover fixed with adhesive tape to the tube mount and rear end of the bronchoscope leads to a significant reduction of aerosol and droplets being distributed within the room (Video 4, Figure 2B, Figure 4). See further material in the online supplement.