Project Publications

Publications prior to PORSAV

Here are some of the key research papers that underlie the PORSAV project. This work was not supported by PORSAV, but provides a foundation for significant parts of the project.

Gas leakage during minimally invasive surgery is an aerosolization hazard. Sensitive optical and thermographic imaging can demonstrate and differentiate between mechanistic categories, enabling engineering solutions to fortify surgical care against pollutants and pathogens affecting operating room teams.

There is ongoing concern regarding the aerosolization hazard of laparoscopy since the outbreak of the COVID-19 pandemic [1,2,3,4]. As a global crisis without precedent in the modern surgical era, expert opinion and theoretical extrapolations dominated initial considerations and directions regarding operative care processes. As elective surgical care restarts again, it’s imperative that we advance in a systemic, scientific way to fortify minimally invasive surgical practice against further waves of this or other airborne pathogens and pollutants [5]. The fundamental driver of any higher risk of intraabdominal pathogen aerosolization by laparoscopy versus laparotomy is the use and leakage of surgical gas, specifically carbon dioxide (CO2) [6]. We set out to develop a reliable model to determine intraoperative unfiltered CO2 leak into the operating room from out of the patient to enable comprehensive understanding and address of this substantial issue. A practical and clinically deployable methodology for leak ascertainment would allow immediate feedback for surgeons intraoperatively regarding factors within their control (e.g., leaks related to skin incision or instrument usage including leaky port seals and uncapped irrigation channels) that otherwise often go unnoticed. It also would allow surgeons share best practice with evidential support and provide reassurance to centers who do not have a significant problem with CO2 leaks. Finally, it would enable rapid testing and iterative development of the many potential adjunctive mechanical solutions (e.g., improved trocar seals and valves, gas leak traps, etc.) including reproducibility in assessment and trialing.

The unfolding COVID‐19 pandemic has challenged surgical care where aerosol‐generating operations may expose the surgical team13. Optimization of theatre airflow management and the application of smoke evacuation devices have been recommended and some personal protective equipment may remain for the foreseeable future13. WHO guidelines advise well‐fitting respirators (for example FFP2/3 or N95 masks) for surgical teams as the minimum where there is exposure risk. These disposable masks are becoming scarce and may not offer the required protection especially when poorly fitted. Powered Air Purifying Respirators (PAPR) are another type of respiratory protection that are validated to offer higher respiratory protection by regulatory bodies (2·5‐100x Airway Protection Factor versus N95 masks). These respirators feature a waist‐mounted battery‐powered pump that blows filtered air into a hood and are reusable. These devices are widely used in other industries but haven’t been formally assessed for operating room teams.

The concept of an intubation box to contain aerosols has been proposed to address the risk of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission to healthcare professionals during airway management. This barrier enclosure method has been widely promoted in the popular media., Although there is a need for innovation, it remains important to fully assess new concepts to ensure their fitness for purpose. To date, the intubation box has only been tested using a vertical cough model using a Sim-man mannikin (Laerdal Medical, Stavenger, Norway). We subjected such a box to objective airflow analysis of its performance with a human volunteer (more relevant to how it would be clinically deployed). We also collated perspectives from potential users in anaesthesia.

The COVID‐19 pandemic has focused surgeons and healthcare systems on the hazards of minimally invasive surgery and its devices [1, 2]. Energy and articulating laparoscopic and robotic instruments contain hollow spaces in their shafts and handles to allow cabling to transmit electrical energy to the instrument tip and tissue. While much attention has been placed on the management of smoke that occurs during cautery by instrument activation [3, 4], it may be less obvious that such instruments may act as chimney flues for intraperitoneal gas to flow unfiltered directly into the operating room environment. This gas will contain smoke but also simply the carbon dioxide (CO2) used to distend the abdominal cavity and any associated aerosolized cells and virions.

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Transanal minimally invasive surgery (TAMIS) and transanal total mesorectal excision (TaTME) are mostly performed using a dedicated access device, namely the Gelpoint Path (Applied Medical, Rancho Santa Margarita, CA, USA). The instability or oscillation of the rectal wall due to variance in pneumorectal distension that frustrated early adopters has been addressed by addition of high flow insufflation systems (e.g. Airslea, Conmed, Milford, CT USA) [1] and, more recently, with an insufflation stablization bag (Applied Medical) [2]. By adding consistency of intrarectal gas volume, these greatly improve precision and fluency in intra- and transrectal surgery.

Minimally invasive surgical procedures have been restricted during the COVID‐19 pandemic, in part to reduce inpatient occupancy and minimize pressure on critical care and anaesthesia but also because of concern about the potential for transmission of infection via aerosols created by laparoscopy [1, 2]. Viral particles have now been identified in the blood, stool [3] and peritoneal fluid [4] of infected patients, although the infectious potential of any such particles that may be carried via surgical gases is unclear.

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Unanticipated behaviours of the Airseal Insufflation and Access System (Conmed, Utica, NY, USA), in the public domain since 2018 [1], have recently been restated by the manufacturer [2] in the light of the COVID‐19 pandemic and widespread concerns regarding aerosolization hazards during surgery [3]. Video S1 illustrates this device’s tendency for intra‐abdominal gas effluvium to be continually blown into the operating room during use as well as it’s phenomenon of air entrainment (i.e. the tendency for room air to be sucked into the abdomen) via the device during high pressure intra‐operative suctioning.

We used a combination of assessment technologies in a high‐fidelity simulation model (fresh porcine cadaver) as well as during clinical surgery to examine gas flow through the Airseal 12‐mm valveless trocar with the Airseal IFS carbon dioxide (CO2) insufflator in Airseal mode. Schlieren Imaging (an optical imaging technology that identifies differences in gas densities) as well as a specific near‐infrared CO2 visualization system (FLIR GF343; Flir Systems Ltd, Kent, ME, UK) were used to dynamically visualize gas flow around the trocar. A specific laparoscopic nebulizer (Aeroneb Solo; Aerogen, Galway, Ireland) enabled abdominal gas and droplet egress visualization by transillumination in a darkened room [4]. A flowmeter (TSI Series 5000; TSI Inc., Shoreview, MI, USA) measured directional velocity of flow just outside of the trocar.

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Elective surgery during the evolving COVID-19 pandemic presents unprecedented logistical challenges to surgical teams. Cleft surgery may be considered an aerosol generating procedure (AGP), which may lead to small-droplet transmission of virions. Strict adherence to personal protective equipment (PPE) policy is used with the hope of preventing transmission of the virus between patients and operating theatre staff.
The World Health Organisation (WHO) guidance for infection prevention and control during health care when COVID-19 is suspected recommends that healthcare workers performing AGPs should use a half-face particulate respirator at least as protective as a European Union (EU) standard Filtering Face Piece 2 (FFP2) respirator or equivalent. Public Health England have published extensive guidance on PPE and the British Association of Plastic, Reconstructive and Aesthetic Surgeons (BAPRAS) has provided interpretation of this for plastic surgeons.Recently published safety recommendations for ear, nose and throat surgery (ENT) also provide useful guidance for plastic surgeons who perform AGPs. The most common types of respirators in healthcare are filtering facepiece (FFP) respirators and powered air purifying respirators (PAPRs). A PAPR is a battery-powered, air-purifying respirator that uses a pump to force air through filter cartridges and into the breathing zone of the wearer within a loose fitting hood.PAPRs provide a higher assigned protection factor to the wearer than a FFP respirator. We sought to investigate compatibility of FFP3 respirators and PAPRs with surgical loupes and the operating microscope, as well as to examine the logistics of performing cleft surgery under these conditions.
A group of cleft surgeons, head and neck surgeons and paediatric dentists attended a PPE workshop at The National Surgical and Clinical Skills Centre (NSCSC) in the Royal College of Surgeons in Ireland on 23 April 2020. Participants had the opportunity to try FFP3 respirators (Biztex Portwest, Westport, Mayo, Ireland) and PAPRs (3 M Scott, Monroe, North Carolina, USA). Participants brought their own loupes and performed tasks in the surgical skills lab, before joining anaesthetic and nursing colleagues in a simulated operating room for a tracheostomy insertion, cleft palate repair and dental examination under general anaesthesia. A brief summary of observations is presented below.