The PanSurg-PREDICT Study: Endocrine Surgery During the COVID-19 Pandemic.

BACKGROUND: In the midst of the COVID-19 pandemic, patients have continued to present with endocrine (surgical) pathology in an environment depleted of resources. This study investigated how the pandemic affected endocrine surgery practice. METHODS: PanSurg-PREDICT is an international, multicentre, prospective, observational cohort study of emergency and elective surgical patients in secondary/tertiary care during the pandemic. PREDICT-Endocrine collected endocrine-specific data alongside demographics, COVID-19 and outcome data from 11-3-2020 to 13-9-2020. RESULTS: A total of 380 endocrine surgery patients (19 centres, 12 countries) were analysed (224 thyroidectomies, 116 parathyroidectomies, 40 adrenalectomies). Ninety-seven percent were elective, and 63% needed surgery within 4 weeks. Eight percent were initially deferred but had surgery during the pandemic; less than 1% percent was deferred for more than 6 months. Decision-making was affected by capacity, COVID-19 status or the pandemic in 17%, 5% and 7% of cases. Indication was cancer/worrying lesion in 61% of thyroidectomies and 73% of adrenalectomies and calcium 2.80 mmol/l or greater in 50% of parathyroidectomies. COVID-19 status was unknown at presentation in 92% and remained unknown before surgery in 30%. Two-thirds were asked to self-isolate before surgery. There was one COVID-19-related ICU admission and no mortalities. Consultant-delivered care occurred in a majority (anaesthetist 96%, primary surgeon 76%). Post-operative vocal cord check was reported in only 14% of neck endocrine operations. Both of these observations are likely to reflect modification of practice due to the pandemic. CONCLUSION: The COVID-19 pandemic has affected endocrine surgical decision-making, case mix and personnel delivering care. Significant variation was seen in COVID-19 risk mitigation measures. COVID-19-related complications were uncommon. This analysis demonstrates the safety of endocrine surgery during this pandemic.

Modelling nasal airflow coefficients: an insight into the nature of airflow.

BACKGROUND: There has been considerable discussion and conflicting views regarding the presence of laminar or turbulent flow within the nose. The aim of this study was to investigate how the modelling of variable flow coefficients can assist in the evalua- tion of the characteristics of flow in the resistive segments of the nose. METHODOLOGY: A comparison was made between the flow coefficient for the nasal valve, obtained from a mathematical model, and resistive flow components such as a Venturi meter and orifice tube. Also, a variable loss coefficient was formulated for the whole (unilateral) nose which, by utilising the intersection of the laminar and turbulent asymptotes, provided an estimation for the critical Reynolds number (Rcrit). RESULTS: The results show that the flow resistance of the nasal valve is considerably greater than that for both a Venturi meter and an orifice tube implying turbulent or turbulent-like flow for much of nasal inspiration. Regarding the loss coefficient for the whole (unilateral) nose, normal respiration flowrates are displaced well away from the laminar asymptote. The critical Reynolds number was estimated to be 450. CONCLUSIONS: A novel method of determining the flow characteristics of the nose, particularly the critical Reynolds number, is presented. The analysis indicates a higher degree of turbulence than is assumed from a simple traditional calculation using a hy- draulic diameter and flow through straight tubes. There are implications for computational fluid dynamics (CFD) modelling where either the entire nasal airflow is assumed to be laminar or a low turbulence model implemented.

Vocal palsy increases the risk of lower respiratory tract infection in low-risk, low-morbidity patients undergoing thyroidectomy for benign disease: A big data analysis.

OBJECTIVES: Thyroidectomy is the commonest operation that places normally functioning laryngeal nerves at risk of injury. Vocal palsy is a major risk factor for dysphonia, dysphagia, and less commonly, airway obstruction. We investigated the association between post-thyroidectomy vocal palsy and long-term risks of pneumonia and laryngeal failure. DESIGN: An N=near-all analysis of the English administrative dataset using a previously validated informatics algorithm to identify young and otherwise low-risk patients undergoing first-time elective thyroidectomy for benign disease. Information about age, sex, morbidities, social deprivation and post-operative and late complications were derived. MAIN OUTCOME MEASURES: Between 2004 and 2012, 43 515 patients between the ages of 20 and 69 who had no history of cancer, neurological, or respiratory disease underwent elective total or hemithyroidectomy without concomitant or late neck dissection, parathyroidectomy or laryngotracheal surgery for benign thyroid disease for the first and only time. Information about age, sex, morbidities and in-hospital and late complications was recorded. RESULTS: Mean age at surgery was 46±12. There was a strong female preponderance (85%), and most patients (89%) had no recorded Charlson comorbidities Most patients (65%) underwent hemithyroidectomy. Late vocal palsy was recorded in 449 (1.03%) patients, and its occurrence was an independent risk factor for emergency hospital readmission (n=7113; Hazard Ratio 1.52; 95% confidence interval 1.21-1.91), hospitalisation for lower respiratory tract infection (n=944; HR 2.04; 95% CI 1.07-3.75), dysphagia (n=564; HR 3.47; 95% CI 1.57-7.65) and gastrostomy/tracheostomy placement (n=80; HR 20.8; 95% CI 2.5-171.2). Independent risk factors for late vocal palsy were age, burden of morbidities, total thyroidectomy, post operative bleeding, male sex, and annual surgeon volume <30. CONCLUSIONS: There is a significant association between post-thyroidectomy vocal palsy and long-term risks of hospital readmission, dysphagia, hospitalisation for lower respiratory tract infection, and gastrostomy/tracheostomy tube placement. This adds weight to the need, from a thyroid surgical perspective, to undertake universal post-thyroidectomy laryngeal surveillance as a minimum standard of care, with a focus on post-operative dysphagia and aspiration, and from a medical/respiratory perspective, to initiate investigations to identify occult vocal palsy in patients who present with pneumonia, who have a history of thyroid surgery.

A national analysis of trends, outcomes and volume-outcome relationships in thyroid surgery.

OBJECTIVES: Thyroid conditions are common, and their incidence is increasing. Surgery is the mainstay treatment for many thyroid conditions, and understanding its utilisation trends and morbidity is central to improving patient care. DESIGN: An N = near-all analysis of the English administrative dataset to identify trends in thyroid surgery specialisation, volume-outcome relationships, and the incidence and risk factors for short- and long-term morbidity. MAIN OUTCOME MEASURES: Between 2004 and 2012, 72 594 patients underwent elective thyroidectomy in England. Information about age, sex, morbidities, nature of thyroid disease and surgery, adjuvant treatments and complications including hypocalcaemia and vocal palsy was recorded. RESULTS: Mean age at surgery was 49 ± 30, and a female predominance (82%) was observed. Most patients underwent hemithyroidectomy (51%) or total thyroidectomy (32%). Patients underwent surgery for benign (52.5%), benign inflammatory (21%) and malignant (17%) thyroid diseases. Thyroid surgery grew by 2.9% a year and increased in specialisation. Increased surgeon volume significantly reduced lengths of stay: the proportion of length of stay outliers fell from 11.8% for patients of occasional thyroidectomists (<5 per year) to 2.8% for patients of high-volume surgeons (>50 thyroidectomies a year). Post-discharge vocal palsy and hypocalcaemia occurred in 1.87% and 1.58% of cases, respectively. High-volume surgeons had a reduced incidence of vocal palsy, and volumes >30 were consistently protective. CONCLUSIONS: Thyroid surgery is increasingly specialised. High-volume surgeons, that is patients who perform 50 or more thyroidectomies per year, achieve lower complications and shorter lengths of stay.

Ventilation tube insertion simulation: a literature review and validity assessment of five training models.

OBJECTIVE: The objective of this study was to identify and investigate the face and content validity of ventilation tube insertion (VTI) training models described in the literature. DESIGN: A review of literature was carried out to identify articles describing VTI simulators. Feasible models were replicated and assessed by a group of experts. SETTING: Postgraduate simulation centre. PARTICIPANTS: Experts were defined as surgeons who had performed at least 100 VTI on patients. Seventeen experts were participated ensuring sufficient statistical power for analysis. MAIN OUTCOME MEASURES: A standardised 18-item Likert-scale questionnaire was used. This addressed face validity (realism), global and task-specific content (suitability of the model for teaching) and curriculum recommendation. RESULTS: The search revealed eleven models, of which only five had associated validity data. Five models were found to be feasible to replicate. None of the tested models achieved face or global content validity. Only one model achieved task-specific validity, and hence, there was no agreement on curriculum recommendation. CONCLUSIONS: The quality of simulation models is moderate and there is room for improvement. There is a need for new models to be developed or existing ones to be refined in order to construct a more realistic training platform for VTI simulation.

Utilisation, Reliability and Validity of Clinical Evaluation Exercise in Otolaryngology Training.

OBJECTIVES: To investigate the utilisation, reliability and validity of clinical evaluation exercise (CEX) in otolaryngology training. DESIGN: Retrospective database analysis. SETTING: Online assessment database. PARTICIPANTS: We analysed all CEXs submitted by north London core (CT) and speciality trainees (ST) in otolaryngology from 2010 to 2013. MAIN OUTCOME MEASURES: Internal consistency of the 7 CEX items rated as either O: outstanding, S: satisfactory or D: development required. Overall performance rating (pS) of 1-4 assessed against completion of training level. Receiver operating characteristic was used to describe CEX sensitivity and specificity. Overall score (cS), pS and the number of 'D'-rated items were used to investigate construct validity. RESULTS: One thousand one hundred and sixty CEXs from 45 trainees were included. CEX showed good internal consistency (Cronbach's alpha= 0.85). CEX was highly sensitive (99%), yet not specific (6%). cS and pS for ST was higher than CT (99.1% ± 0.4 versus 96.6% ± 0.8 and 3.06 ± 0.05 versus 1.92 ± 0.04, respectively P < 0.001). pS showed a significant stepwise increase from CT1 to ST6 (P < 0.001). In contrast, cS only showed improvement up to ST4 (P = 0.025). The most frequently utilised item 'management and follow-up planning' was found to be the best predictor of cS and pS (rs  = +0.69 and +0.21, respectively). CONCLUSION: CEX is reliable in assessing early years otolaryngology trainees in clinical examination, but not at higher level. It has the potential to be used in a summative capacity in selecting trainees for ST positions. This would also encourage trainees to master all domains of otolaryngology clinical examination by end of CT.

Utilisation and outcomes of case-based discussion in otolaryngology training.

OBJECTIVES: To assess the reliability, validity and outcomes of Case-based Discussion (CBD) in otolaryngology training. DESIGN: Retrospective database analysis. SETTING: National electronic database. PARTICIPANTS: North London otolaryngology trainees. MAIN OUTCOME MEASURES: We tested the tool's reliability along with its capacity to denote trainee progress. A score was calculated (cS) and compared across core (CT) and specialty trainees (ST) at all levels. The number of items rated as "development required" (D) was also examined. RESULTS: One thousand four hundred and fifty-six CBDs were submitted by 46 trainees from 2007 to 2013, averaging 13.6 per trainee per year. Items relating to knowledge, management and judgement were more popular (98% usage), and better predictors of cS compared to other parameters (rs: +0.74, +0.70 and +0.72, respectively). CBD was found to be reliable (Cronbach's α = 0.848) and highly sensitive (99%), yet not specific. cS was significantly higher in ST than CT (95.3% ± 0.6 versus 88.7% ± 1.3). pS showed a similar pattern (3.15 ± 0.4 versus 2.0 ± 0.05) (P < 0.001). cS and pS increased from CT1 to ST8 (rs: +0.60 and +0.34, respectively). The number of D-rated items decreased with increasing year of training. CONCLUSION: Case-based discussion is a reliable and valid tool in otolaryngology training. It is highly sensitive but not specific. Trainees should be encouraged to use it at all levels.

Do flow volume loops alter surgical management in patients with a goitre?

INTRODUCTION: Flow volume loops (FVLs) are considered part of the workup of patients with thyroid enlargement presenting to the endocrinology clinic. They are used to detect upper airway obstruction (UAO) secondary to tracheal compression (TC) from a goitre. Surgical assessment in contrast tends to focus on clinical evaluation supplemented when required by imaging. The aim of this study was to investigate whether FVLs influence the decision to operate in patients with a goitre. METHODS: We identified patients with a goitre referred by the department of endocrinology for FVLs between 2006 and 2011. The results of the FVL were collated, and their impact on patient management was assessed. RESULTS: Ninety-six patients were referred for FVL. In 38 patients, the indication was specifically to evaluate the effects of a goitre. Of these, 33 were reported as normal. Five FVLs were reported as abnormal (3 suggesting lung pathology and 2 TC). Both patients with TC on FVL presented no CT evidence of TC and underwent surgery due to abnormal cytology. Of the 33 normal FVLs, 7 underwent surgery: 2 for local compression, 4 for abnormal cytology and 1 for Graves' disease. None of the FVLs influenced the decision to operate. CONCLUSION: FVLs may detect subradiological TC, but rarely influence management in patients with a goitre. In view of this and the cost of £235 per investigation, FVL should be reserved for goitre patients with suspected primary lung pathology, where the distinction between large and small airway compression is likely to influence management.

Does direct observation of procedural skills reflect trainee's progress in otolaryngology?

BACKGROUND: UK surgical trainees are required to undertake work-based assessments each year in order to progress in their training. Direct Observation of Procedural Skills (DOPS) is one of these assessments. We aim to investigate the validity of DOPS in assessing otolaryngology trainees at all levels. METHODS: A retrospective search of the portfolios of all otolaryngology trainees in North Thames was carried out to identify otolaryngology-specific DOPS. A score (Cs) was calculated for each DOPS based on the percentage of satisfactorily-rated items. The overall performance rating (Ps) was analysed as a separate variable and compared with Cs. The Ps and Cs results were then compared across trainee grades and levels within each grade: Core trainees (CT1-CT2) and specialty trainees (ST3-ST8). RESULTS: Seven hundred and sixty-seven otolaryngology DOPS were completed between August 2008 and September 2013. The tool was found to be reliable and internally consistent. Trainees in ST grade had higher Cs and Ps scores than CT grade (P < 0.001). Pairwise comparison showed that both Cs and Ps increased from CT1 to ST3 (P = 0.005) but not from ST4 onwards (P = 0.198). CONCLUSIONS: Otolaryngology DOPS is a useful tool in assessing otolaryngology trainees especially from CT1-ST3 level. DOPS can also differentiate between junior and senior trainees. However, it was not able to demonstrate progress at levels above ST3, most likely due to the simplicity of the procedures which trainees tend to master in the first few years of training.

Serum phosphate predicts temporary hypocalcaemia following thyroidectomy.

BACKGROUND: Temporary hypocalcaemia occurs in up to 40% of patients following a total thyroidectomy. Serum calcium and parathyroid hormone (PTH) measurements are currently used to predict post-thyroidectomy hypocalcaemia. However, immediate access to PTH measurement is expensive and not widely available. Serum phosphate responds rapidly to changes in circulating PTH levels, and its measurement is readily available in all hospitals. We evaluated the use of serum phosphate to predict temporary hypocalcaemia post-thyroidectomy. METHODS: We retrospectively assessed 111 consecutive patients who had total or completion thyroidectomy. Patients had serum calcium and phosphate measured preoperatively, on the evening of surgery (day 0), on the morning of day 1 and over the following week as clinically indicated. Serum PTH was measured on the morning of day 1. Vitamin D levels were measured preoperatively. RESULTS: Seventy-six patients did not develop treatment-demanding hypocalcaemia. In these patients, the mean serum phosphate concentration was lower on the morning of day 1 compared to that on the evening of surgery. Seventeen patients with a vitamin D>25 nmol/l developed hypocalcaemia requiring treatment from day 1 onwards. All had an overnight rise in serum phosphate to >1.44 mmol/l (100% sensitivity and specificity for predicting hypocalcaemia). Twelve patients who had a vitamin D<25 nmol/l also developed hypocalcaemia but had an attenuated rise in serum phosphate. CONCLUSION: Serum phosphate is a reliable biochemical predictor of post-thyroidectomy hypocalcaemia in patients without vitamin D deficiency. The use of serum phosphate may facilitate safe day 1 discharge of patients undergoing thyroidectomy.

Video-assisted thoracoscopic surgery for ectopic mediastinal parathyroid adenoma.

Background: Primary hyperparathyroidism (PHPT), caused by an ectopic mediastinal parathyroid adenoma, is uncommon. In the past, when the adenoma was not accessible from the neck, median sternotomy was advocated for safe and successful parathyroidectomy. Video-assisted thoracoscopic surgical (VATS) parathyroidectomy represents a modern alternative approach to this problem. Methods: Information on patients undergoing VATS was obtained from a specific database, including clinical presentation, biochemistry, preoperative imaging, surgical approach and patient outcomes. A comprehensive literature review was undertaken to draw comparisons with other publications. Results: Over a 2-year period, nine patients underwent VATS parathyroidectomy for sporadic PHPT. Five patients had persistent PHPT following previous unsuccessful parathyroidectomy via cervicotomy, and four had had no previous parathyroid surgery. The median duration of surgery was 90 (range 60-160) min. Eight patients were cured biochemically, with no major complications. One patient required conversion to a median sternotomy for removal of a thymoma that had resulted in false-positive preoperative imaging. Conclusion: With appropriate preoperative imaging, multidisciplinary input and expertise, VATS parathyroidectomy is an effective, safe and well tolerated approach to ectopic mediastinal parathyroid adenoma.

Antecedentes: El hiperparatiroidismo primario (primary hyperparathyroidism, pHPT) causado por un adenoma paratiroideo ectópico mediastínico es infrecuente. Hace años, cuando un adenoma no era accesible por vía cervical se propugnaba una esternotomía media para efectuar una paratiroidectomía segura y con éxito. La paratiroidectomía por cirugía toracoscópica asistida por video (video­assisted thoracoscopic surgical, VATS) es una alternativa moderna para el abordaje de esta patología. Métodos: La información de los pacientes tratados con VATS se obtuvo de una base de datos específica, incluyendo presentación clínica, bioquímica, radiología preoperatoria, abordaje quirúrgico y resultados de los pacientes. Se efectuó una revisión extensa de la literatura para efectuar comparaciones con otras publicaciones. Resultados: Durante un periodo de 2 años, 9 pacientes fueron tratados mediante paratiroidectomía por VATS debido a un pHPT esporádico, de los cuales 5 presentaban pHPT persistente después del fracaso de una paratiroidectomía por cervicotomía, mientras que los 4 restantes no habían sido operados previamente de cirugía paratiroidea. El tiempo medio operatorio fue de 101 minutos (rango 60­160). Ocho pacientes se curaron bioquímicamente, sin ninguna complicación mayor. Un paciente precisó conversión a una esternotomía media para extirpar un timoma que había sido un falso positivo en la radiología preoperatoria. Conclusión: La paratiroidectomía por VATS es una intervención efectiva, segura y bien tolerada para la extirpación de un adenoma ectópico mediastínico, siempre y cuando se disponga de radiología preoperatoria adecuada, equipo multidisciplinar y experiencia.

Scar satisfaction and body image in thyroidectomy patients: prospective study in a tertiary referral centre.

BACKGROUND: This study is the first to evaluate scar satisfaction and body image in thyroidectomy patients using validated assessment tools. METHODS: A total of 123 thyroidectomy patients were recruited over 8 months. Both patients and clinicians completed assessment tools that included: the Manchester Scar Scale (to measure scar perception), Dysmorphic Concern Questionnaire (to assess body image), Body Dysmorphic Concern Questionnaire (to screen for body dysmorphic disorder) and EQ-5D (to measure life quality). A separate image panel comprising experts and non-experts assessed 15 scar photographs. The results were analysed using non-parametric descriptive statistics. RESULTS: Poor body image was associated with poor scar perception (ρ = 0.178, p = 0.05). Poor life quality correlated with poor scar perception (ρ = -0.292, p = 0.001). Scar length did not affect scar perception. Prevalence of body dysmorphic disorder among patients was found to be 8.94 per cent, which is higher than general population rates. CONCLUSION: Negative body image and life quality impact negatively upon scar perception.

Assessment of progress and competence in tonsillectomy surgery using cumulative sum analysis.

OBJECTIVE: To assess the feasibility of using cumulative sum analysis to show trainees' performance curves and highlight concerns in tonsillectomy surgery. METHODS: In this prospective study, the performance of eight otolaryngology trainees (in their first 6-12 months in the specialty) was compared to that of experts (over 150 tonsillectomies performed) in terms of operative time and post-operative complications. Cumulative sum analysis curves were generated to highlight trainees' performance, and were updated after each performance. RESULTS: The average operative time was 23 minutes (standard deviation = 11) for experts and 38 minutes (standard deviation = 16) for trainees (p < 0.0001). Cumulative sum analysis charts for trainees' operative time initially rose and then started to plateau after a number of cases (range, 25-30), while that of experts remained low. Cumulative sum analysis charts for complications can be used to monitor performance. In this study, complications were combined (because of low incidence) to allow use of this outcome measure. CONCLUSION: The flexibility of the cumulative sum analysis makes it adaptable to any outcome. It is a strong adjunct in surgical training to monitor progress and competence. Its sensitivity also allows early detection of poor performance, to instigate intervention.

Computational fluid dynamics benchmark dataset of airflow in tracheas.

Computational Fluid Dynamics (CFD) is fast becoming a useful tool to aid clinicians in pre-surgical planning through the ability to provide information that could otherwise be extremely difficult if not impossible to obtain. However, in order to provide clinically relevant metrics, the accuracy of the computational method must be sufficiently high. There are many alternative methods employed in the process of performing CFD simulations within the airways, including different segmentation and meshing strategies, as well as alternative approaches to solving the Navier-Stokes equations. However, as in vivo validation of the simulated flow patterns within the airways is not possible, little exists in the way of validation of the various simulation techniques. The data presented here consists of very highly resolved flow data. The degree of resolution is compared to the highest necessary resolutions of the Kolmogorov length and time scales. Therefore this data is ideally suited to act as a benchmark case to which cheaper computational methods may be compared. A dataset and solution setup for one such more efficient method, large eddy simulation (LES), is also presented.

Stem cells.

Stem cells derived from adult and embryonic sources have great therapeutic potential, but much research is still needed before their clinical use becomes commonplace. There is debate about whether adult stem cells can be used instead of those derived from embryos. Rationalisation is needed but can be exercised only once the various cells have been carefully compared and contrasted under appropriate experimental conditions. Some characteristics that might help resolve the issue of cell source can already be applied to the debate. Accessibility is important; some adult cells, such as neural stem cells, are difficult to obtain, at least from living donors. Other factors include the frequency and abundance of adult stem cells and their numbers and potency, which might decline with age or be affected by disease. For embryonic stem cells, ethical concerns have been raised, and the proposed practice of therapeutic cloning tends to be misrepresented in the lay media. For both adult and embryonic stem cells, stability, potential to transmit harmful pathogens or genetic mutations, and risk of forming unwanted tissues or even teratocarcinomas have yet to be fully assessed.

How advances in light technology have shaped ENT.

The development of light technologies, allowing anatomical visualisation of otherwise hidden structures, led to significant advances in ENT in the nineteenth and twentieth centuries. Natural light from the sun, and from candles, was initially harnessed using mirrors. Later, the invention of limelight and electricity preceded the emergence of the modern-day endoscope, which, in tandem with the discovery of coherent fibre-optics in the 1950s, significantly expanded the surgical repertoire available to otolaryngologists. This study aimed to trace the rich history of ENT through the specialty's use of light.

Power loss mechanisms in pathological tracheas.

The effort required to inhale a breath of air is a critically important measure in assessing airway function. Although the contribution of the trachea to the total flow resistance of the airways is generally modest, pathological alterations in tracheal geometry can have a significant negative effect. This study investigates the mechanisms of flow energy loss in a healthy trachea and in four geometries affected by retrosternal goitre which can cause significant distortions of tracheal geometry including constriction and deviation with abnormal curvature. By separating out the component of energy loss related to the wall shear (frictional loss), striking differences are found between the patterns of energy dissipation in the normal and pathological tracheas. Furthermore the ratio of frictional to total loss is dramatically reduced in the pathological geometries.

The effects of curvature and constriction on airflow and energy loss in pathological tracheas.

This paper considers factors that play a significant role in determining inspiratory pressure and energy losses in the human trachea. Previous characterisations of pathological geometry changes have focussed on relating airway constriction and subsequent pressure loss, however many pathologies that affect the trachea cause deviation, increased curvature, constriction or a combination of these. This study investigates the effects of these measures on tracheal flow mechanics, using the compressive goitre (a thyroid gland enlargement) as an example. Computational fluid dynamics simulations were performed in airways affected by goitres (with differing geometric consequences) and a normal geometry for comparison. Realistic airways, derived from medical images, were used because idealised geometries often oversimplify the complex anatomy of the larynx and its effects on the flow. Two mechanisms, distinct from stenosis, were found to strongly affect airflow energy dissipation in the pathological tracheas. The jet emanating from the glottis displayed different impingement and breakdown patterns in pathological geometries and increased loss was associated with curvature.