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.