Minimising exposure to droplet and aerosolised pathogens: a computational fluid dynamics study.

BACKGROUND: Hazardous pathogens are spread in either droplets or aerosols produced during aerosol-generating procedures (AGP). Adjuncts minimising exposure of healthcare workers to hazardous pathogens released during AGP may be beneficial. We used state-of-the-art computational fluid dynamics (CFD) modelling to optimise the performance of a custom-designed shield. METHODS: We modelled airflow patterns and trajectories of particles (size range 1-500 µm) emitted during a typical cough using CFD (ANSYS Fluent software, Canonsburg, PA, USA), in the presence and absence of a protective shield enclosing the head of a patient. We modelled the effect of different shield designs, suction tube position, and suction flow rate on particle escape from the shield. RESULTS: Use of the shield prevented escape of 99.1-100% of particles, which were either trapped on the shield walls (16-21%) or extracted via suction (79-82%). At most, 0.9% particles remained floating inside the shield. Suction flow rates (40-160 L min-1) had no effect on the final location of particles in a closed system. Particle removal from within the shield was optimal when a suction catheter was placed vertically next to the head of the patient. Addition of multiple openings in the shield reduced the purging performance from 99% at 160 L min-1 to 67% at 40 L min-1. CONCLUSION: CFD modelling provides information to guide optimisation of the efficient removal of hazardous pathogens released during AGP from a custom-designed shield. These data are essential to establish before clinical use, pragmatic clinical trials, or both.

SIR Flat CAP (Safety In Radiology - Flat-Packed Compact Airborne Precaution): A Low-Cost, Portable, Negative-Pressure Isolation Barrier Shield for Protecting Frontline Healthcare Workers.

Introduction Multiple barrier shields have been described since the start of the COVID-19 pandemic. Most of these are bulky and designed for use in the main anesthetic or radiology departments. We developed a portable, negative-pressure barrier shield designed specifically for portable ultrasound examinations. A novel supine cough generation model was developed together with a reverse qualitative fit test to simulate real-world aerosol droplet generation and dispersion for evaluating the effectiveness of the barrier shield. We report the technical specifications of this design, named "SIR Flat CAP" from Safety In Radiology - Flat-packed Compact Airborne Precaution, as well as its performance in reducing the spread of droplets and aerosols.  Methods The barrier shield was constructed using 1 mm acrylic panels, clear packing tape, foam double-sided tape, and surgical drapes. Negative pressure was provided via hospital wall suction. A supine cough generation model was developed to simulate cough droplet dispersal. A reverse qualitative fit test was used to assess for airborne transmission of microdroplets. Results The supine cough generation model was able to replicate similar results to previously reported supine human cough generation dispersion. The use of the barrier shield with negative-pressure suction prevented the escape of visible droplets, and no airborne microdroplets were detected by reverse qualitative fit testing from the containment area. Conclusions The barrier shield significantly reduces the escape of visible and airborne droplets from the containment area, providing an additional layer of protection to front-line sonographers.

The effectiveness of the Safety in Interventional Radiology (SIR) Shield in reducing droplet transmission and its effect on image quality and radiation dose.

OBJECTIVE: To evaluate the efficacy of a barrier shield in reducing droplet transmission and its effect on image quality and radiation dose in an interventional suite. METHODS: A human cough droplet visualisation model in a supine position was developed to assess efficacy of barrier shield in reducing environmental contamination. Its effect on image quality (resolution and contrast) was evaluated via image quality test phantom. Changes in the radiation dose to patient post-shield utilisation was measured. RESULTS: Use of the shield prevented escape of visible fluorescent cough droplets from the containment area. No subjective change in line-pair resolution was observed. No significant difference in contrast-to-noise ratio was measured. Radiation dosage to patient was increased; this is predominantly attributed to the increased air gap and not the physical properties of the shield. CONCLUSION: Use of the barrier shield provided an effective added layer of personal protection in the interventional radiology theatre for aerosol generating procedures. ADVANCES IN KNOWLEDGE: This is the first time a human supine cough droplet visualisation has been developed. While multiple types of barrier shields have been described, this is the first systematic practical evaluation of a barrier shield designed for use in the interventional radiology theatre.

Factors affecting length of stay after percutaneous biliary interventions.

OBJECTIVE:: To evaluate the factors affecting the length of hospital stay (LOS) after percutaneous transhepatic biliary drainage (PTBD). METHODS:: A retrospective review of all patients who had undergone PTBD with or without stenting at a UK specialist centre between 2005 and 2016 was conducted. RESULTS:: 692 patients underwent 1976 procedures over 731 clinical episodes for which, the median age was 65 (range 18-100) years, and the median Charlson Index was 3. PTBD was performed for malignant (n = 563) and benign strictures (n = 60), stones (n = 62), and bile leaks (n = 46). The median LOS was 13 (range 0-157) days, and the median interprocedure duration was 9 (range 0-304) days. The median number of procedures per patient was 2 and the median number of days required to complete a set of procedures for a patient (TBID) ranged from 0 to 557 days, with a median of 16 (interquartile range: 8-32) days. Patients with biliary leak had the highest LOS. Biliary stents were mostly placed at the second stage at a median of 6 (range 0-120) days from the first procedure day. Placement of a biliary stent in the first stage of the procedure was associated with shorter LOS (p < 0.001). CONCLUSIONS:: Biliary stenting at index procedure reduces LOS, although it is not always technically possible. Patients with bile leak managed with PTBD have longer LOS. ADVANCES IN KNOWLEDGE:: This study provides data which can help in appropriate consenting, better planning, and efficient resource utilization for patients undergoing PTBD.

Meteorological Controls on Local and Regional Volcanic Ash Dispersal.

Volcanic ash has the capacity to impact human health, livestock, crops and infrastructure, including international air traffic. For recent major eruptions, information on the volcanic ash plume has been combined with relatively coarse-resolution meteorological model output to provide simulations of regional ash dispersal, with reasonable success on the scale of hundreds of kilometres. However, to predict and mitigate these impacts locally, significant improvements in modelling capability are required. Here, we present results from a dynamic meteorological-ash-dispersion model configured with sufficient resolution to represent local topographic and convectively-forced flows. We focus on an archetypal volcanic setting, Soufrière, St Vincent, and use the exceptional historical records of the 1902 and 1979 eruptions to challenge our simulations. We find that the evolution and characteristics of ash deposition on St Vincent and nearby islands can be accurately simulated when the wind shear associated with the trade wind inversion and topographically-forced flows are represented. The wind shear plays a primary role and topographic flows a secondary role on ash distribution on local to regional scales. We propose a new explanation for the downwind ash deposition maxima, commonly observed in volcanic eruptions, as resulting from the detailed forcing of mesoscale meteorology on the ash plume.

Repeated negative biopsies in isolated high-grade cystic duct dysplasia with progression to adenocarcinoma.

Cystic and bile duct dysplasia is a rare histological finding, especially when found in the absence of an underlying malignancy. We report a patient who presented with jaundice and weight loss. Clinical and cytological evidence suggested a diagnosis of cholangiocarcinoma and the patient underwent a pancreatico-duodenectomy. Histopathological examination suggested a diagnosis of two foci of biliary dysplasia: cystic duct and lower common bile duct. Fifteen months later, the patient re-presented with signs of obstructive jaundice and biliary sepsis. Although CT scan revealed images highly indicative of metastatic disease, repeated biopsies failed to confirm this. Eventually a liver biopsy did reveal moderately differentiated adenocarcinoma, however oncological interventional was no longer appropriate and the patient was managed palliatively. This case report focuses on the current understanding of progression of biliary dysplasia.

Trauma-induced secondary cardiac injury is associated with hyperacute elevations in inflammatory cytokines.

INTRODUCTION: Clinical evidence supports the existence of a trauma-induced secondary cardiac injury. Experimental research suggests inflammation as a possible mechanism. The study aimed to determine if there was an early association between inflammation and secondary cardiac injury in trauma patients. METHODS: A cohort study of critically injured patients between January 2008 and January 2010 was undertaken. Levels of the cardiac biomarkers troponin I and heart-specific fatty acid-binding protein and the cytokines tumor necrosis factor α (TNF-α), interleukin (IL)-6, IL-1ß, and IL-8 were measured on admission to hospital, and again at 24 and 72 h. Participants were reviewed for adverse cardiac events (ACEs) and in-hospital mortality. RESULTS: Of 135 patients recruited, 18 (13%) had an ACE. Patients with ACEs had higher admission plasma levels of TNF-α (5.4 vs. 3.8 pg/mL; P = 0.03), IL-6 (140 vs. 58.9 pg/mL, P = 0.009), and IL-8 (19.3 vs. 9.1 pg/mL, P = 0.03) compared with those without events. Hour 24 cytokines were not associated with events, but IL-8 (14.5 vs. 5.8 pg/mL; P = 0.01) and IL-1ß (0.55 vs. 0.19 pg/mL; P = 0.04) were higher in patients with ACEs at 72 hours. Admission IL-6 was independently associated with heart-specific fatty acid-binding protein increase (P < 0.05). Patients who presented with an elevated troponin I combined with either an elevated TNF-α (relative risk [RR], 11.0; 95% confidence interval [CI], 1.8-66.9; P = 0.015), elevated IL-6 (RR, 17.3; 95% CI, 2.9-101.4; P = 0.001), or elevated IL-8 (RR, 15.0; 95% CI, 3.1-72.9; P = 0.008) were at the highest risk of in-hospital death when compared with individuals with normal biomarker and cytokine values. CONCLUSIONS: There is an association between hyperacute elevations in inflammatory cytokines with cardiac injury and ACEs in critically injured patients. Biomarker evidence of cardiac injury and inflammation on admission is associated with a higher risk of in-hospital death.

Portal vein embolization using a nitinol plug (Amplatzer vascular plug) in combination with histoacryl glue and iodinized oil: adequate hypertrophy with a reduced risk of nontarget embolization.

The purpose of this study was to assess whether portal vein embolization (PVE) using a nitinol vascular plug in combination with histoacryl glue and iodinized oil minimizes the risk of nontarget embolization while obtaining good levels of future liver remnant (FLR) hypertrophy. Between November 2005 and August 2008, 16 patients (8 females, 8 males; mean age, 63 +/- 3.6 years), each with a small FLR, underwent right ipsilateral transhepatic PVE prior to major hepatectomy. Proximal PVE was initially performed by placement of a nitinol vascular plug, followed by distal embolization using a mixture of histoacryl glue and iodinized oil. Pre- and 6 weeks postprocedural FLR volumes were calculated using computed tomographic imaging. Selection for surgery required an FLR of 0.5% of the patient's body mass. Clinical course and outcome of surgical resection for all patients were recorded. At surgery, the ease of hepatectomy was subjectively assessed in comparison to previous experience following PVE with alternative embolic agents. PVE was successful in all patients. Mean procedure time was 30.4 +/- 2.5 min. Mean absolute increase in FLR volume was 68.9% +/- 12.0% (p = 0.00005). There was no evidence of nontarget embolization during the procedure or on subsequent imaging. Nine patients proceeded to extended hepatectomy. Six patients demonstrated disease progression. One patient did not achieve sufficient hypertrophy in relation to body mass to undergo hepatic resection. At surgery, the hepatobiliary surgeons observed less periportal inflammation compared to previous experience with alternative embolic agents, facilitating dissection at extended hepatectomy. In conclusion, ipsilateral transhepatic PVE using a single nitinol plug in combination with histoacryl glue and iodinized oil simplifies the procedure, offering short procedural times with minimal risk of nontarget embolization. Excellent levels of FLR hypertrophy are achieved enabling safe extended hepatectomy.

Total percutaneous aortic repair: midterm outcomes.

The purpose of this study was to examine the immediate and midterm outcomes of percutaneous endovascular repair of thoracic and abdominal aortic pathology. Between December 2003 and June 2005, 21 patients (mean age: 60.4 +/- 17.1 years; 15 males, 6 females) underwent endovascular stent-graft insertion for thoracic (n = 13) or abdominal aortic (n = 8) pathology. Preprocedural computed tomographic angiography (CTA) was performed to assess the suitability of aorto-iliac and common femoral artery (CFA) anatomy, including the degree of CFA calcification, for total percutaneous aortic stent-graft repair. Percutaneous access was used for the introduction of 18- to 26-Fr delivery devices. A 'preclose' closure technique using two Perclose suture devices (Perclose A-T; Abbott Vascular) was used in all cases. Data were prospectively collected. Each CFA puncture site was assessed via clinical examination and CTA at 1, 6, and 12 months, followed by annual review thereafter. Minimum follow-up was 36 months. Outcome measures evaluated were rates of technical success, conversion to open surgical repair, complications, and late incidence of arterial stenosis at the site of Perclose suture deployment. A total of 58 Perclose devices were used to close 29 femoral arteriotomies. Outer diameters of stent-graft delivery devices used were 18 Fr (n = 5), 20 Fr (n = 3), 22 Fr (n = 4), 24 Fr (n = 15), and 26 Fr (n = 2). Percutaneous closure was successful in 96.6% (28/29) of arteriotomies. Conversion to surgical repair was required at one access site (3.4%). Mean follow-up was 50 +/- 8 months. No late complications were observed. By CT criteria, no patient developed a >50% reduction in CFA caliber at the site of Perclose deployment during the study period. In conclusion, percutaneous aortic stent-graft insertion can be safely performed, with a low risk of both immediate and midterm access-related complications.

Endovascular management of acute blunt traumatic thoracic aortic injury: a single center experience.

BACKGROUND: Traumatic injury of the thoracic aorta is a life-threatening complication in patients who sustain deceleration or crush injuries. The magnitude of force necessary to cause blunt thoracic aortic injury results in a high proportion of concomitant injuries, posing a significant challenge for prioritizing management. Open surgical mortality is increased in the presence of coexisting head, lung, and abdominal injuries. Spinal cord ischemia may occur following aortic cross-clamping and operative hypotension. Endovascular stent-graft placement offers a safe, effective, and timely treatment option. The aim of this study was to assess our single center experience of endovascular repair following acute blunt traumatic aortic injury. METHODS: Data from thirteen consecutive patients (mean age, 43.2 years; range, 16 to 84 years) with acute blunt traumatic aortic injury treated by endovascular stent-graft insertion between October 2001 and March 2007 was prospectively collected. Demographics, injury characteristics, technique, and complications were recorded. Follow-up data consisted of computed tomographic angiography and plain chest radiography at regular intervals. Mean and median follow-up after stent-graft implantation were 28.9 and 29 months, respectively. RESULTS: All patients underwent endovascular repair within a median of 9 hours from hospital presentation. Two patients underwent carotico-carotid bypass immediately prior to endovascular stenting during a single anesthetic. Stent-graft implantation was technically successful in all patients. No patient required conversion to open surgical repair of the acute blunt traumatic aortic injury. Procedure-related paraplegia was zero. Complications included proximal migration of initial stent-graft in one patient and iliac artery avulsion in another patient with consequent ilio-femoral bypass. The median hospital stay was 17 days. There were no in-hospital deaths. CONCLUSION: Endovascular repair is evolving as the procedure of choice for acute blunt traumatic aortic injury. Treatment of lesions that extend into the aortic arch is feasible with extra-anatomical bypass. In our study, endovascular repair of blunt traumatic aortic injury is a safe procedure with low morbidity and a mortality rate of zero.