MATERIALS AND METHODS
All patients who underwent tracheostomy in the Division of Head and Neck Surgery of the Department of Surgery, The University of Hong Kong at Queen Mary Hospital and Gleneagles Hong Kong Hospital between 01 April 2020 and 17 April 2020 were included.
All operations were performed by a consultant surgeon accompanied by 1 scrub nurse and 1 consultant anaesthetist. Full barrier protection was adopted by all three parties. Intubation under general anaesthesia was performed by anaesthetist. Two horizontal anaesthetic screen supports were then placed and secured with universal rotary clamps on patient’s left bedside: 1 anaesthetic screen support was placed at head level making sure not to limit the anaesthetist’s view and working space; the other was placed at the level of patient’s umbilicus at a height of 20cm from patient’s truncal surface. (Figure 1) The lower anaesthetic screen could be placed further apart and set at a greater height to ensure adequate working space for the operating surgeon. Skin was prepared and draped with disposable surgical drapes (3M Hong Kong) in the usual manner for tracheostomy, exposing the inferior border of mandible, bilateral neck and sternal angle. The 2 anaesthetic screen supports were covered by surgical drapes.
A clear and sterile plastic sheet measuring 120cm x 140cm was placed over the operating field. The sheet was then pulled taut and secured over the operating field using sterile clips for mounting on the 2 horizontal anaesthetic screens. The caudal and left lateral edge of the plastic sheet was sealed using adhesive 3M tape. The cranial end of the sterile drape was not taped to allow manipulation of endo-tracheal tube by anaesthetist. The right side of the plastic sheet was not taped to allow the surgeon to operate from beneath. (Figure 2) A 1cm puncture was made over the left upper corner of the central operating field for placement of smoke evacuation suction tubing. The hole was sealed and tubing secured with Tegaderm (3M Hong Kong). Suction for smoke evacuation was only used during tissue dissection with monopolar diathermy prior to tracheotomy. (Figure. 3)
Scrub nurse was positioned opposite the surgeon’s right hand. Tracheostomy was performed as described by Wei, ensuring good communication with our anaesthetic colleague throughout the operation. [11] Skin incision was performed with scalpel knife, followed by soft tissue dissection with monopolar diathermy. Tracheotomy was performed with a scalpel knife after securing haemostasis and all suction devices switched off. After insertion of a cuffed Portex tracheostomy tube of appropriate size, the cuff was inflated. The tracheostomy tube was connected to a ventilator tubing which was passed under the plastic sheet and sterile drapes on the side of ventilator. Ventilation was resumed by the anaesthetist once closed ventilation circuit was secured. Tracheostomy tube was secured with 4 stitches using 3/0 Nylon once successful ventilation was confirmed.
On completion of tracheostomy, the central and bilateral surfaces of the plastic sheet were marked with 7cm x 7cm grids. (Figure 4) (Table 1). The face shield of surgeon and scrub nurse was removed after tracheostomy. The face shield used was a piece of optically clear, latex free plastic film measuring 32cm in length and 22cm in width with foam forehead cushion and elastic strap (A R Medicom Inc (Asia) Ltd.). It covered a full face length from forehead to neck, with outer edges of the face shield reaching bilateral ears. It had anti-fog and anti-glare properties with no hearing restrictions. Each face shield was put against a white background with 12 grids measuring 7cm x 7cm each to facilitate counting at maximal magnification. Each plastic sheet was carefully removed and placed against a white background for counting.
The number and size of droplets splashed in each grid of the plastic sheet and face shield was counted using the surgical microscope Leica M720 0H5 (Leica Microsystems GmbH, Germany). The plastic sheets and face shields were discarded once counting was complete.
Operative diagnosis; operation duration; size, number and distribution of droplets on plastic shield and face shield for each party were documented.