Self-contamination during doffing
Our study demonstrated considerable self-contamination during doffing. This result raised concerns on pathogen contamination of the skin or clothes of HCWs during PPE removal, which may result in self-inoculation and spread of the virus to patients and other HCWs through contaminated body fluids, including blood, urine, vomitus and stool. Gastrointestinal fluid losses of patients with EVD can be massive (5–10 L/day), droplet dispersion can be greater than 10 ft. and serum viral loads of dying patients with EVD can reach 10 billion copies/mL [
15]. Given that no licensed vaccines nor proven effective antiviral therapies for EVD are currently available, PPE plays a crucial role in mitigating the risk of HCW exposure to contaminated body fluids in the care of patients with EVD [
16].
The frequent occurrence of self-contamination during PPE doffing is also consistent with the findings of previous studies [
6‐
8,
13‐
21]. The most likely contaminated areas include the neck, hands and fingers, arms and wrists and face [
14,
17]. A study conducted in South Korea that estimated the degree of contamination during PPE doffing of HCWs reported that the most vulnerable processes comprise the removal of the respirator, shoe cover and hood [
3].
The current study indicated that contamination of the working clothes occurred less frequently during PPE1 removal than during the removal of PPE2 and PPE3, which may be due to the ergonomic features of individual PPEs under testing. PPE1 consists of a neck-to-ankle outfit and includes a hood covering the neck. PPE2 is a head-to-ankle overall, and is a PPE ensemble frequently used in overseas settings to prevent Ebola transmission [
3,
10,
11]. However, PPE removal is complicated because of the head-to-ankle, one-piece design and the elastication in the facial opening, wrists and ankles. HCWs have to take off the hood, unzip the front zipper, remove the overall and outer gloves together and place the trousers on the chair, thereby resulting in easy contamination of the hair and head, hands, working clothes, clogs and chair [
17]. The elasticated one-piece coverall hood creates a potential contamination risk because the elastic contracts and pulls the outer part of the hood inwards and towards the participants’ hair and neck during removal [
22]. The zipper and its flap are also placed along the PPE2 centre front. Therefore, a plastic apron is worn to minimise the risk of body fluids being trapped in the zipper region. Herlihey et al. [
22] also reported that when the subjects unzip the coverall, the zipper is stuck in the surrounding fabric or the gloves are stuck to the adhesive of the PPE, while unsealing the flaps covering the zipper results in ripping [
22].
The WHO protocol requires the overall to be removed from top to bottom, followed by the removal of outer gloves whilst pulling the arms out of the sleeves of the overall. Special caution is needed to prevent self-contamination. PPE3 is recommended by HA for routine patient care, in which the neck, lower part of the legs and shoes are incompletely covered. Compared with PPE 1, additional sites, including the neck, arms, working clothes and clogs, were heavily contaminated when wearing PPE3 because it cannot provide adequate protection for HCWs caring for patients with EVD. These contaminated regions may be caused by self-contamination during doffing and contamination when the fluorescent solution was sprayed. Considering the possible underclothing contamination during doffing, the working clothes worn under the PPE ensembles should be frequently changed, especially when contamination is suspected.
During PPE1 or PPE2 doffing, the participants have to wear the clean clogs after removing their boots. However, the clogs may be possibly contaminated by the gowns or the environment in some cases. Hence, using footwear covers is an unideal option. During boot cover removal, HCWs struggle to balance their legs in the air [
20]. Shoe covers are also difficult to doff, thereby often requiring assistance and increasing the risk of cross-contamination among workers [
22].
The CDC and WHO recommend the use of double gloving with at least the outer pair possessing an extended cuff that reaches beyond the wrist [
6] to decrease the incidence of hand contamination and provide improved protection for HCWs during PPE removal [
16,
23]. Although double gloving is incorporated into the protocols for PPE use, the removal of the outer and inner gloves should be done with caution, followed by proper hand hygiene.
Previous studies defined contamination as small fluorescent stains (<1cm
2) and large patches (>1cm
2) [
8,
13,
14] and revealed that fluorescent stain sizes are affected during gown removal [
8]. In the present study, a precise estimation of the contaminated regions was performed in terms of the size of patches, that is, small (≤1cm
2), medium (1cm
2 to <3cm
2), large (≥1cm
2 to 5cm
2), or extra large (≥5cm
2). The stain sizes can be associated with either inadequate PPE coverage or because of self-contamination during PPE removal. For example, PPE3 cannot fully cover the neck of the participants, which resulted in many small or extra-large patches in the anterior and posterior neck region after spraying of the fluorescent solution onto the face shield and anterior surfaces of the gown. Meanwhile, PPE2 offers a high coverage area during fluorescent solution spraying. However, the hair/head, hands or wrists of the participants were heavily contaminated with extra-large patches during PPE removal. Similarly, medium-sized patch contamination can be due to either the PPE design or self-contamination. Therefore, a PPE with a high coverage area and simple ergonomic features that can minimise the risk of recontamination during doffing should be designed.
In this study, the older staff showed significantly less small-sized contaminated patches on their working clothes than the younger staff. This result may be due to the additional cautiousness of the older staff, whilst working than the younger staff. However, this finding cannot be generalised because of the low number of older staff (n = 4) who participated in this study.
Environmental contamination
In addition to self-contamination of HCWs during PPE doffing, environmental contaminations, such as those in the lid of the rubbish bin, chair, faucet and sink, were observed. Human-to-human transmission of EVD is also possible via indirect contact with the environment contaminated with such fluids [
24]. The virus can survive for several hours on dry surfaces, such as doorknobs and countertops, to several days at room temperature in body fluids, such as blood [
25]; virus-positive samples were still observed 7 days post-mortem [
16].
Considering that hand hygiene methods using alcohol hand sanitiser fail to remove the fluorescent solution, handwashing with soap and water was performed by the participants. Thus, the sink may be contaminated because of handwashing, and the working clothes that came in contact with the sink may be contaminated because of the repeated handwashing. These results suggested that the height and width of the sink must be at a good working level of HCWs to prevent self-contamination during handwashing. Although alcohol gel is commonly used nowadays during PPE donning/doffing, hand cleansing with soap and water is recommended in cases of visible contamination in various situations, such as when areas are contaminated by vomitus, respiratory secretions, or fecal matter. Discarding used PPEs should be given much attention because of frequent contamination of rubbish bin covers [
13].
Protocol deviations and importance of training
Deviations of the donning procedure may increase the risk of self-contamination whilst doffing [
20]. Although the participants watched a video on PPE donning and doffing to familiarise themselves with the steps on the day of testing, they can also refer to the posters related to the procedures available in the venue. PPE1 exhibited the lowest overall deviation rate among the three PPE ensembles during doffing (2.95, 9.48 and 3.52% for PPE1, PPE2 and PPE3, respectively). This finding was expected because of the complexity of PPE2, as described above. The highest deviation rate (58.33%) was observed during the simultaneous removal of the overall and outer gloves in PPE2. As mentioned above, this result agrees with the WHO protocol for doffing overall [
12]. This protocol requires the participants to remove the inner gloves, which were covered by the coverall. This procedure is difficult for many participants because they can only ‘feel’ the inner gloves during removal and cannot see them. Therefore, several participants cannot remove the overall and outer gloves together, or in certain situations, they removed both the inner and outer gloves simultaneously. Apart from the emphasis on regular training for HCWs to perform the procedure smoothly, the doffing procedure should be evaluated to increase its practicability for the users.
Being an international aviation hub, Hong Kong is frequently visited by travellers from all around the world. Moreover, contacts between Mainland China and African countries are becoming increasingly frequent. Although most HCWs in Hong Kong possess inadequate experience in handling EVD cases, providing regular training for HCWs is necessary to fill the gap between the desired PPE performance and actual practice. Contamination errors caused by unfamiliarity with the procedures, complexity with PPE ensembles and unconscious habits can be prevented through repeated practice and training. Evidence shows that traditional learning methods (e.g., watching educational videos and learning PPE guidelines) are inferior to immersive learning methods, including audio-visual devices and active learning involvement using simulation training that includes feedback on performance for clinical management of EVD cases, in guiding the PPE procedures [
3,
17,
26,
27].
On the average, participants used the longest time for donning and doffing PPE2, followed by PPE1 and PPE3. A study reported that HCWs may show poor compliance with proper PPE removal protocol because of time constraints [
28]. The most time-consuming processes include removing the shoe covers, putting on gloves and removing the outer gloves [
3]. Thus, a short duration of doffing PPE is important for the faultless completion of removal protocol. Familiarisation of the HCWs with the procedures via frequent training and improved ergonomic features is necessary for the PPE design not only to prevent HCWs from self-contamination but also to shorten PPE donning and doffing time.