MATERIALS AND METHODS
All patients who underwent surgery for head and neck cancer 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 March 2020 and 09 April 2020 were included.
All patients underwent comprehensive work-up for tumour staging including clinical and endoscopic examination of the upper aerodigestive tract, and ultrasonography of the neck +/- fine needle aspiration for cytology of suspected neck nodal metastasis with full barrier protection. Magnetic resonance imaging +/- whole-body positron emission tomography scans were also performed for tumour staging.
Admission to head and neck surgical ward was only allowed (1) on declaring absence of travel history 14 days prior to surgery, (2) absence of close contact with confirmed cases, and (3) tympanic body temperature <37.5 degrees Celsius taken at ward entrance. On admission, routine bloods including white cell count and chest X-ray were checked. As recommended by Centre for Health Protection in Hong Kong (CHP) and Queen Mary Hospital Infection Control Unit, PCR would only be tested for febrile and symptomatic patients +/- radiological changes on chest X-ray.
All operations were performed by a consultant surgeon and two assistants who have completed their fellowship in head and neck surgery. Skin incisions and tracheotomies were performed using scalpel knife. Reciprocating and oscillating saws were used for maxillary swing and manubrial resection respectively. Monopolar and bipolar diathermy was used for tissue dissection and haemostasis.
Full barrier protection was adopted by all three surgeons and one scrub nurse. The face shield used was a piece of optically clear, latex free plastic film imported from China measuring 32cm in length and 22cm in width with foam forehead cushion and elastic strap. 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.
The face shield of each surgeon and scrub nurse was removed after each procedure. Each face shield was put against a white background with 12 grids measuring 7cm x 7cm each to facilitate counting at maximal magnification (Figure 1). The number and size of droplets splashed was counted for each face shield using the surgical microscope Leica M720 0H5 (Leica Microsystems GmbH, Germany) (Figure 2). Droplet distribution per face shield was plot on a separate sheet with the same grid as that used in Figure 1 (Figure 3). Each of the 12 grids were labelled 1 to 12 (Figure 4). Counting and plotting of droplets splashed were performed by a surgeon who did not participate in the operation. The face shields were discarded once counting was complete.
Operative diagnosis and procedure; size, average number and distribution of droplets on face shield for each party were documented.