An interview with Dr Chew Hui Sing, Consultant, Department of Otorhinolaryngology (ENT), Tan Tock Seng Hospital on safeguarding the clinical environment from the spread of airborne viral particles.
As COVID-19 continues and the threat of airborne diseases looms, how can we ensure our clinics and hospitals remain a safe space for both patients and healthcare workers alike? While standard surgical masks have proved effective in containing the spread of viral particles, this is not the case for aerosols, which puts a high risk on aerosol-generating procedures.
In this interview, we speak to Dr Chew Hui Sing, a consultant in the Department of Otorhinolaryngology (ENT) at Tan Tock Seng Hospital, on the National Healthcare Group’s latest invention—the Aerodrop Duo—to curb the spread of airborne diseases.
With COVID-19, the use of masks has been commonplace. Can you briefly explain how do masks work in containing the spread of airborne diseases?
Firstly, it serves as a source control to prevent the spread of infection from an infected individual (who may or may not have displayed symptoms). Secondly, it serves to protect an otherwise uninfected individual from acquiring the airborne infection.
In general, masks are multi-layered with varying filtration efficiency resulting in inhibition of airborne virus/bacteria transmission depending on the mask’s material type, design, and fit, as well as the size of the contaminant.
Apart from masks, what other precautions are being taken to safeguard against airborne diseases? For example, perhaps the use of UV light for disinfection? Are these measures sufficient in a clinical setting to prevent the spread of viral respiratory aerosols?
Other measures include, but not limited to, ensuring good efficient ventilation, regular disinfection of high-touch contact surfaces, use of personal protective equipment, reinforcement on hand hygiene, and proper patient placement (e.g. isolating or cohorting infected patients).
These measures are adequate in a normal setting. However, additional precautions are necessary under special circumstances. An example would be conducting aerosol-generating procedures due to the nature that the aerosols could potentially penetrate surgical masks.
I do not have any experience with the use of UV light (UVC) in disinfection to allow me to comment on its role and efficacy. It is, however, not a commonly deployed method due to several limitations and the potential risks that could result in eye damage, skin irritation, ageing, and skin cancer.
In May 2022, you launched the Aerodrop Duo, an environmentally-friendly dual-function high-efficiency particulate (HEPA) filtration scope mask system. How did this idea come about and were there any challenges you encountered along the way?
The COVID-19 pandemic has resulted in a heightened awareness of the infection transmission risks associated with some of the common procedures that we usually perform. As an ENT specialist, we perform scope procedures (e.g. nasoendoscopy and laryngoscopy) commonly in our daily practice to diagnose and manage conditions pertaining to the ear, nose, and throat.
During such procedures, the patient is unmasked, awake, and usually in an upright seated position. The introduction of the scope into the patient’s nose and throat, even in the presence of local anaesthetic spray, may trigger coughs or sneezes. In addition, the patient may be asked to speak during such procedures to allow for evaluation of the vocal cords’ movements. This results in aerosols and droplets, which may contain viruses being released into the surrounding environment.
These droplets and aerosols may stay in the air or land on surfaces resulting in potential infection transmission. These scope procedures are therefore considered high-risk procedures during the pandemic and were even deferred for non-urgent cases during its peak. However, as we know, COVID-19 will not be our last encounter with healthcare pandemics. We need to allow clinic services to resume in a safe and logistically efficient manner, and also be prepared for the next disease X.
Hence, we thought of a simple idea targeting source control to solve this clinical problem, which is the development of a containment scope mask for a patient to wear during the conduct of ENT scope procedures. In addition, we also conceptualised the development of a dedicated fully titratable dual-function HEPA filtration system capable of powering the containment mask (additional suction of the scope mask environment serves as a 2nd layer of protection) while filtering ambient clinic air ( 3rd layer of protection) to provide a safer clinic space for everyone. This allows us to resume clinical service sustainably, without compromising the safety of our patients and healthcare workers.
With this idea in mind, we approached the Centre for Medical Technology and Innovation (CMTI), which linked me up with The Biofactory to provide the necessary engineering expertise to help reduce the idea into practice. We also set up a multidisciplinary team comprising ENT, engineering, research, and infection disease experts to ensure that our prototype and final device not only meet its intent but also fulfil the infection disease requirements.
We did encounter several challenges in its development, which included technical issues with the prototype designs, study experiments and evaluation, which were all thankfully resolved after multiple rounds of troubleshooting with the engineering expertise from The Biofactory. There were also considerable delays to the study due to COVID-19 restrictions and delays in sourcing materials. The various innovation-related research administrative requirements such as collaboration and service agreements, the filing for intellectual property, waiver of competition applications, HSA checks, and other legal documents were also completely new to me. I am thankful for the kind support and guidance from CMTI and CRIO on these matters.
As we move towards living with COVID-19 and in anticipation of other respiratory transmitted diseases that may surface in the future, how does the Aerodrop Duo work?
It will help to reduce environmental contamination arising from aerosols or droplets that might occur during the conduct of aerosol-generating procedures (AGP). This prevents potential infection and transmission among patients, healthcare workers, or other individuals in the vicinity. Patients don’t walk in with a diagnosis and there may be asymptomatic carriers as well. Hence, this device helps protect against transmission of future unknown disease X, which may occur during the conduct of AGPs.
Since its launch, how successful has the Aerodrop Duo been in reducing environmental aerosol contamination?
We conducted an experimental study to evaluate the efficacy of this device. When it comes to the effectiveness of the prototype mask in reducing particle emission, we observed a slower rate of particle emission when the prototype mask is used compared to without mask, across all four types of activities.
Particle emission rate over time was significantly slower for the prototype mask for the smallest sized particle (0.3 µm) during breathing, speaking, and singing, when compared to no mask. Compared to no mask and the standard surgical mask, under experimental conditions, the mean fold reduction in the rate of rise of cumulative particle counts resulting from prototype mask usage was estimated to be 4.89 and 1.83 for speaking, 5 and 2.43 for singing, 21 and 29 for coughing, respectively. We have published our findings in an international peer-reviewed journal and you can find more details regarding the innovation and its efficacy here: Innovative dual-function protective scope mask and filtration system for aerosol generating ENT scope procedures.1
Going forward, how do you plan to implement this device in other departments within the hospital? Taking it further, would you see this device expanding into the home for usage by infected persons under home quarantine, for example?
Firstly, we aim to equip all our ENT rooms with the system in phases. Subsequently, we will be equipping other areas where ENT scope procedures are also being performed, such as the wards and emergency department (ED). Our external collaborator is currently working with the ED to improvise this concept to a smaller filtration unit for patient transport purposes.
In terms of home usage, while it is an interesting consideration for future usage, people generally would prioritise comfort in their homes. Therefore, putting on a mask at home, while under quarantine, might not be an attractive concept. However, if there’s a way that this system or concept can provide comfort and convenience from home, then it can be worth considering.
- Chew, H. S., Tan, M., Sanchalika, A., Tan, G., Ho, E. C., Ang, B. S. P., ... & Yeo, S. B. (2022). Innovative dual function protective scope mask and filtration system for aerosol generating ENT scope procedures. Laryngoscope Investigative Otolaryngology.
About the Interviewee
Dr Chew Hui Sing
Consultant, Department of Otorhinolaryngology (ENT), Tan Tock Seng Hospital