Quantifying the reduction of airborne infectious virus load using a ventilated patient hood

BACKGROUND

Healthcare workers treating SARS-CoV-2 patients are at risk of infection by respiratory exposure to patient-emitted, virus-laden aerosols. Source control devices such as ventilated patient isolation hoods have been shown to limit the dissemination of non-infectious airborne particles in laboratory tests, but data on their performance in mitigating the airborne transmission risk of infectious viruses are lacking.

AIM

We used an infectious airborne virus to quantify the ability of a ventilated hood to reduce infectious virus exposure in indoor environments.

METHODS

We nebulized 10⁹ plaque forming units (pfu) of bacteriophage PhiX174 virus into a ∼30-m³ room when the hood was active or inactive. The airborne concentration of infectious virus was measured by BioSpot-VIVAS and settle plates using plaque assay quantification on the bacterial host Escherichia coli C. The airborne particle number concentration (PNC) was also monitored continuously using an optical particle sizer.

FINDINGS

The median airborne viral concentration in the room reached 1.41 × 10⁵ pfu/m³ with the hood inactive. When active, the hood reduced infectious virus concentration in air samples by 374-fold. The deposition of infectious virus on the surface of settle plates was reduced by 87-fold. This was associated with a 109-fold reduction in total airborne particle number escape rate.

CONCLUSION

A personal ventilation hood significantly reduced airborne particle escape, considerably lowering infectious virus contamination in an indoor environment. Our findings support the further development of source control devices to mitigate nosocomial infection risk among healthcare workers exposed to airborne viruses in clinical settings.

Vented Individual Patient (VIP) Hoods for the Control of Infectious Airborne Diseases in Healthcare Facilities

By providing a means of separating the airborne emissions of patients from the air breathed by healthcare workers (HCWs), vented individual patient (VIP) hoods, a form of local exhaust ventilation (LEV), offer a new approach to reduce hospital-acquired infection (HAI). Results from recent studies have demonstrated that, for typical patient-emitted aerosols, VIP hoods provide protection at least equivalent to that of an N95 mask. Unlike a mask, hood performance can be easily monitored and HCWs can be alerted to failure by alarms. The appropriate use of these relatively simple devices could both reduce the reliance on personal protective equipment (PPE) for infection control and provide a low-cost and energy-efficient form of protection for hospitals and clinics. Although the development and deployment of VIP hoods has been accelerated by the coronavirus disease 2019 (COVID-19) pandemic, these devices are currently an immature technology. In this review, we describe the state of the art of VIP hoods and identify aspects in need of further development, both in terms of device design and the protocols associated with their use. The broader concept of individual patient hoods has the potential to be expanded beyond ventilation to the provision of clean conditions for individual patients and personalized control over other environmental factors such as temperature and humidity.

Action guidance for addressing pollution from inhalational anaesthetics

Climate change is a real and accelerating existential danger. Urgent action is required to halt its progression, and everyone can contribute. Pollution mitigation represents an important opportunity for much needed leadership from the health community, addressing a threat that will directly and seriously impact the health and well‐being of current and future generations. Inhalational anaesthetics are a significant contributor to healthcare‐related greenhouse gas emissions and minimising their climate impact represents a meaningful and achievable intervention. A challenge exists in translating well‐established knowledge about inhalational anaesthetic pollution into practical action. CODA is a medical education and health promotion charity that aims to deliver climate action‐oriented recommendations, supported by useful resources and success stories. The CODA‐hosted platform is designed to maximise engagement of the global healthcare community and draws upon diverse experiences to develop global solutions and accelerate action. The action guidance for addressing pollution from inhalational anaesthetics is the subject of this article. These are practical, evidence‐based actions that can be undertaken to reduce the impact of pollution from inhalational anaesthetics, without compromising patient care and include: removal of desflurane from drug formularies; decommissioning central nitrous oxide piping; avoidance of nitrous oxide use; minimising fresh gas flows during anaesthesia; and prioritising total intravenous anaesthesia and regional anaesthesia when clinically safe to do so. Guidance on how to educate, implement, measure and review progress on these mitigation actions is provided, along with means to share successes and contribute to the essential, global transition towards environmentally sustainable anaesthesia.

Principles of environmentally-sustainable anaesthesia: a global consensus statement from the World Federation of Societies of Anaesthesiologists

The Earth's mean surface temperature is already approximately 1.1°C higher than pre-industrial levels. Exceeding a mean 1.5°C rise by 2050 will make global adaptation to the consequences of climate change less possible. To protect public health, anaesthesia providers need to reduce the contribution their practice makes to global warming. We convened a Working Group of 45 anaesthesia providers with a recognised interest in sustainability, and used a three-stage modified Delphi consensus process to agree on principles of environmentally sustainable anaesthesia that are achievable worldwide. The Working Group agreed on the following three important underlying statements: patient safety should not be compromised by sustainable anaesthetic practices; high-, middle- and low-income countries should support each other appropriately in delivering sustainable healthcare (including anaesthesia); and healthcare systems should be mandated to reduce their contribution to global warming. We set out seven fundamental principles to guide anaesthesia providers in the move to environmentally sustainable practice, including: choice of medications and equipment; minimising waste and overuse of resources; and addressing environmental sustainability in anaesthetists' education, research, quality improvement and local healthcare leadership activities. These changes are achievable with minimal material resource and financial investment, and should undergo re-evaluation and updates as better evidence is published. This paper discusses each principle individually, and directs readers towards further important references.

Quantitative evaluation of aerosol generation during manual facemask ventilation

Manual facemask ventilation, a core component of elective and emergency airway management, is classified as an aerosol-generating procedure. This designation is based on one epidemiological study suggesting an association between facemask ventilation and transmission during the SARS-CoV-1 outbreak in 2003. There is no direct evidence to indicate whether facemask ventilation is a high-risk procedure for aerosol generation. We conducted aerosol monitoring during routine facemask ventilation and facemask ventilation with an intentionally generated leak in anaesthetised patients. Recordings were made in ultraclean operating theatres and compared against the aerosol generated by tidal breathing and cough manoeuvres. Respiratory aerosol from tidal breathing in 11 patients was reliably detected above the very low background particle concentrations with median [IQR (range)] particle counts of 191 (77-486 [4-1313]) and 2 (1-5 [0-13]) particles.l-1 , respectively, p = 0.002. The median (IQR [range]) aerosol concentration detected during facemask ventilation without a leak (3 (0-9 [0-43]) particles.l-1 ) and with an intentional leak (11 (7-26 [1-62]) particles.l-1 ) was 64-fold (p = 0.001) and 17-fold (p = 0.002) lower than that of tidal breathing, respectively. Median (IQR [range]) peak particle concentration during facemask ventilation both without a leak (60 (0-60 [0-120]) particles.l-1 ) and with a leak (120 (60-180 [60-480]) particles.l-1 ) were 20-fold (p = 0.002) and 10-fold (0.001) lower than a cough (1260 (800-3242 [100-3682]) particles.l-1 ), respectively. This study demonstrates that facemask ventilation, even when performed with an intentional leak, does not generate high levels of bioaerosol. On the basis of this evidence, we argue facemask ventilation should not be considered an aerosol-generating procedure.

The effect of intensive care unit admission on smokers' attitudes and their likelihood of quitting smoking

We sought to estimate the proportion of patients admitted to a metropolitan intensive care unit (ICU) who were current smokers, and the relationships between ICU survivors who smoked and smoking cessation and/or reduction six months post-ICU discharge. We conducted a prospective cohort study at a metropolitan level III ICU in Melbourne, Victoria. One hundred consecutive patients who met the inclusion criteria were included in the study. Inclusion criteria consisted of patients who were smokers at time of ICU admission, had an ICU length of stay greater than one day, survived to ICU discharge, and provided written informed consent. A purpose-designed questionnaire which included the Fagerstrom test for nicotine dependence and evaluation of patients' attitude towards smoking cessation was completed by participants following ICU discharge and prior to hospital discharge. Participants were re-interviewed over the phone at six months post-ICU discharge. Of the 1,062 patients admitted to ICU, 253 (23%) were current smokers and 100 were enrolled. Six months post-ICU discharge, 28 (33%) of the 86 participants who were alive and contactable had quit smoking and 35 (41%) had reduced smoking. The median number of reported cigarettes smoked per day reduced by 40%. Participants who initially believed their ICU admission was smoking-related were more likely to have quit six months post-ICU discharge (odds ratio 2.98; 95% confidence interval 1.07 to 8.26; <i>P</i>=0.036). Six months post-ICU discharge, 63/86 (74%) of participants had quit or reduced their smoking. Further research into targeted smoking cessation counselling for ICU survivors is indicated.

Financial and environmental costs of reusable and single-use anaesthetic equipment

BACKGROUND.

An innovative approach to choosing hospital equipment is to consider the environmental costs in addition to other costs and benefits.

METHODS.

We used life cycle assessment to model the environmental and financial costs of different scenarios of replacing reusable anaesthetic equipment with single-use variants. The primary environmental costs were CO 2 emissions (in CO 2 equivalents) and water use (in litres). We compared energy source mixes between Australia, the UK/Europe, and the USA.

RESULTS.

For an Australian hospital with six operating rooms, the annual financial cost of converting from single-use equipment to reusable anaesthetic equipment would be an AUD$32 033 (£19 220), 46% decrease. In Australia, converting from single-use to reusable equipment would result in an increase of CO 2 emissions from 5095 (95% CI: 4614-5658) to 5575 kg CO 2 eq (95% CI: 5542-5608), a 480 kg CO 2 eq (9%) increase. Using the UK/European power mix, converting from single-use (5575 kg CO 2 eq) to reusable anaesthetic equipment (802 kg CO 2 eq) would result in an 84% reduction (4873 kg CO 2 eq) in CO 2 emissions, whilst in the USA converting to reusables would have led to a 2427 kg CO 2 eq (48%) reduction. In Australia, converting from single-use to reusable equipment would more than double water use from 34.4 to 90.6 kilolitres.

CONCLUSIONS.

For an Australian hospital with six operating rooms, converting from single-use to reusable anaesthetic equipment saved more than AUD$30 000 (£18 000) per annum, but increased the CO 2 emissions by almost 10%. The CO 2 offset is highly dependent on the power source mix, while water consumption is greater for reusable equipment.

The financial and environmental costs of reusable and single-use plastic anaesthetic drug trays

We modelled the financial and environmental costs of two commonly used anaesthetic plastic drug trays. We proposed that, compared with single-use trays, reusable trays are less expensive, consume less water and produce less carbon dioxide, and that routinely adding cotton and paper increases financial and environmental costs. We used life cycle assessment to model the financial and environmental costs of reusable and single-use trays. From our life cycle assessment modelling, the reusable tray cost (Australian dollars) $0.23 (95% confidence interval [CI] $0.21 to $0.25) while the single-use tray alone cost $0.47 (price range of $0.42 to $0.52) and the single-use tray with cotton and gauze added was $0.90 (no price range in Melbourne). Production of CO2 was 110 g CO2 (95% CI 98 to 122 g CO2) for the reusable tray, 126 g (95% CI 104 to 151 g) for single-use trays alone (mean difference of 16 g, 95% CI -8 to 40 g) and 204 g CO2 (95% CI 166 to 268 g CO2) for the single-use trays with cotton and paper Water use was 3.1 l (95% CI 2.5 to 3.7 l) for the reusable tray, 10.4 l (95% CI 8.2 to 12.7 l) for the single-use tray and 26.7 l (95% CI 20.5 to 35.4 l) for the single-use tray with cotton and paper Compared with reusable plastic trays, single-use trays alone cost twice as much, produced 15% more CO2 and consumed three times the amount of water Packaging cotton gauze and paper with single-use trays markedly increased the financial, energy and water costs. On both financial and environmental grounds it appears difficult to justify the use of single-use drug trays.

Wasp sting mortality in Australia

Wasp sting fatalities have rarely been reported in Australia. We used data from the Australian Bureau of Statistics and State coronial authorities to investigate deaths from wasp stings in Australia from 1979 through 1998. Seven cases were identified, all involving men in rural settings. Five of the seven victims had prior histories of wasp or bee venom allergy, or both, but none carried injectable adrenalin. All patients with a history of systemic Hymenoptera sting allergy should undergo assessment for immunotherapy and carry adrenalin.