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1.
Surg Endosc ; 36(9): 7047-7055, 2022 09.
Article in English | MEDLINE | ID: covidwho-1941654

ABSTRACT

INTRODUCTION: The advent of the COVID-19 pandemic led to recommendations aimed at minimizing the risk of gas leaks at laparoscopy. As this has continuing relevance including regarding operating room pollution, we empirically quantified carbon dioxide (CO2) leak jet velocity (important for particle propulsion) occurring with different instruments inserted into differing trocars repeated across a range of intra-abdominal pressures (IAPs) and modern insufflators in an experimental model. METHOD: Laparoscopic gas plume leak velocity (metres/second) was computationally enumerated from schlieren optical flow videography on a porcine cadaveric laparoscopic model with IAPs of 4-5, 7-8, 12-15 and 24-25 mmHg (repeated with 5 different insufflators) during simulated operative use of laparoscopic clip appliers, scissors, energy device, camera and staplers as well as Veres needle (positive control) and trocar obturator (negative control) in fresh 5 mm and 12 mm ports. RESULTS: Close-fitting solid instruments (i.e. cameras and obturators) demonstrated slower gas leak velocities in both the 5 mm and 12 mm ports (p = 0.02 and less than 0.001) when compared to slimmer instruments, however, hollow instrument designs were seen to defy this pattern with the endoscopic linear stapler visibly inducing multiple rapid jests even when compared to similarly sized clip appliers (p = 0.03). However, on a per device basis the operating instrumentation displayed plume speeds which did not vary significantly when challenged with varying post size, IAP and a range of insufflators. CONCLUSION: In general, surgeon's selection of instrument, port or pressure does not usefully mitigate trocar CO2 leak velocity. Instead better trocar design is needed, helped by a fuller understanding of trocar valve mechanics via computational fluid dynamics informed by relevant surgical modelling.


Subject(s)
COVID-19 , Insufflation , Laparoscopy , Animals , Carbon Dioxide , Humans , Laparoscopy/adverse effects , Pandemics , Swine
2.
PLoS One ; 17(1): e0262547, 2022.
Article in English | MEDLINE | ID: covidwho-1643266

ABSTRACT

High Flow Nasal Oxygen (HFNO) therapy offers a proven means of delivering respiratory support to critically ill patients suffering from viral illness such as COVID-19. However, the therapy has the potential to modify aerosol generation and dispersion patterns during exhalation and thereby put healthcare workers at increased risk of disease transmission. Fundamentally, a gap exists in the literature with regards to the effect of the therapy on the fluid dynamics of the exhalation jet which is essential in understanding the dispersion of aerosols and hence quantifying the disease transmission risk posed by the therapy. In this paper, a multi-faceted approach was taken to studying the aerosol-laden exhalation jet. Schlieren imaging was used to visualise the flow field for a range of expiratory activities for three healthy human volunteers receiving HFNO therapy at flow rates of 0-60 L/min. A RANS turbulence model was implemented using the CFD software OpenFOAM and used to perform a parametric study on the influence of exhalation velocity and duration on the dispersion patterns of non-evaporating droplets in a room environment. A dramatic increase in the turbulence of the exhalation jet was observed when HFNO was applied. Quantitative analysis indicated that the mean exhalation velocity was increased by 2.2-3.9 and 2.3-3 times that for unassisted breathing and coughing, respectively. A 1-2 second increase was found in the exhalation duration. The CFD model showed that small droplets (10-40 µm) were most greatly affected, where a 1 m/s increase in velocity and 1 s increase in duration caused an 80% increase in axial travel distance.


Subject(s)
Oxygen Inhalation Therapy/methods , Particulate Matter , Humans , Models, Theoretical
3.
Drug Deliv ; 29(1): 10-17, 2022 Dec.
Article in English | MEDLINE | ID: covidwho-1577575

ABSTRACT

Aerosol therapy is used to deliver medical therapeutics directly to the airways to treat respiratory conditions. A potential consequence of this form of treatment is the release of fugitive aerosols, both patient derived and medical, into the environment and the subsequent exposure of caregivers and bystanders to potential viral infections. This study examined the release of these fugitive aerosols during a standard aerosol therapy to a simulated adult patient. An aerosol holding chamber and mouthpiece were connected to a representative head model and breathing simulator. A combination of laser and Schlieren imaging was used to non-invasively visualize the release and dispersion of fugitive aerosol particles. Time-varying aerosol particle number concentrations and size distributions were measured with optical particle sizers at clinically relevant positions to the simulated patient. The influence of breathing pattern, normal and distressed, supplemental air flow, at 0.2 and 6 LPM, and the addition of a bacterial filter to the exhalation port of the mouthpiece were assessed. Images showed large quantities of fugitive aerosols emitted from the unfiltered mouthpiece. The images and particle counter data show that the addition of a bacterial filter limited the release of these fugitive aerosols, with the peak fugitive aerosol concentrations decreasing by 47.3-83.3%, depending on distance from the simulated patient. The addition of a bacterial filter to the mouthpiece significantly reduces the levels of fugitive aerosols emitted during a simulated aerosol therapy, p≤ .05, and would greatly aid in reducing healthcare worker and bystander exposure to potentially harmful fugitive aerosols.


Subject(s)
Aerosols , COVID-19 , Drug Delivery Systems , Infectious Disease Transmission, Patient-to-Professional/prevention & control , Nebulizers and Vaporizers , Respiratory Therapy , Aerosols/administration & dosage , Aerosols/adverse effects , COVID-19/prevention & control , COVID-19/transmission , Computer Simulation , Drug Delivery Systems/instrumentation , Drug Delivery Systems/methods , Equipment Design , Humans , Infection Control/methods , Models, Biological , Particle Size , Respiratory Therapy/adverse effects , Respiratory Therapy/instrumentation , Respiratory Therapy/methods , SARS-CoV-2
4.
Eur J Ophthalmol ; 32(4): 2445-2451, 2022 Jul.
Article in English | MEDLINE | ID: covidwho-1354692

ABSTRACT

OBJECTIVE: To assess the patterns of patient generated aerosol in the context of ophthalmic surgery and ophthalmic examinations. To inform medical teams regarding potential hazards and suggest mitigating measures. METHODS: Qualitatively, real-time time videography assessed exhalation patterns from simulated patients under different clinical scenarios using propylene glycol from an e-cigarette. Quantitatively, high-speed Schlieren imaging was performed to enable high resolution recordings analysable by MATLAB technical computing software. RESULTS: Without a face mask, the standard prior to COVID 19, vapour was observed exiting through the opening in the drape over the surgical field. The amount of vapour increased when a surgical mask was worn. With a taped face mask, the amount of vapour decreased and with inclusion of a continuous suction device, the least amount of vapour was seen. These results were equivocal when the patient was supine or sitting upright. High-speed Schlieren imaging corroborated these findings and in addition showed substantial increase in airflow egress during coughing and with ill-fitting face masks. CONCLUSION: Advising patients to wear a surgical mask at the time of ophthalmic interventions potentially contaminants the ocular field with patient generated aerosol risking endophthalmitis. Surgeon safety can be maintained with personal protective equipment to mitigate the increased egress of vapour from the surgical drape and taping, with or without suction is advisable, whilst meticulous hygiene around lenses is required at the time of slit lamp examination.


Subject(s)
COVID-19 , Electronic Nicotine Delivery Systems , Endophthalmitis , Aerosols , COVID-19/prevention & control , Endophthalmitis/surgery , Humans , Personal Protective Equipment
5.
Br J Anaesth ; 125(3): e293-e295, 2020 09.
Article in English | MEDLINE | ID: covidwho-260341
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