Assessment of UHF Frequency Range for Failure Classification in Power Transformers.

Ultrahigh-frequency (UHF) sensing is one of the most promising techniques for assessing the quality of power transformer insulation systems due to its capability to identify failures like partial discharges (PDs) by detecting the emitted UHF signals. However, there are still uncertainties regarding the frequency range that should be evaluated in measurements. For example, most publications have stated that UHF emissions range up to 3 GHz. However, a Cigré brochure revealed that the optimal spectrum is between 100 MHz and 1 GHz, and more recently, a study indicated that the optimal frequency range is between 400 MHz and 900 MHz. Since different faults require different maintenance actions, both science and industry have been developing systems that allow for failure-type identification. Hence, it is important to note that bandwidth reduction may impair classification systems, especially those that are frequency-based. This article combines three operational conditions of a power transformer (healthy state, electric arc failure, and partial discharges on bushing) with three different self-organized maps to carry out failure classification: the chromatic technique (CT), principal component analysis (PCA), and the shape analysis clustering technique (SACT). For each case, the frequency content of UHF signals was selected at three frequency bands: the full spectrum, Cigré brochure range, and between 400 MHz and 900 MHz. Therefore, the contributions of this work are to assess how spectrum band limitation may alter failure classification and to evaluate the effectiveness of signal processing methodologies based on the frequency content of UHF signals. Additionally, an advantage of this work is that it does not rely on training as is the case for some machine learning-based methods. The results indicate that the reduced frequency range was not a limiting factor for classifying the state of the operation condition of the power transformer. Therefore, there is the possibility of using lower frequency ranges, such as from 400 MHz to 900 MHz, contributing to the development of less costly data acquisition systems. Additionally, PCA was found to be the most promising technique despite the reduction in frequency band information.

Racial disparities in presentation and outcomes for endovascular abdominal aortic aneurysm repair.

OBJECTIVE: In the present study, we used a national database to identify racial differences in the presentation and outcomes for patients undergoing endovascular abdominal aortic aneurysm (AAA) repair (EVAR) and identified areas for improving their care. METHODS: We queried the EVAR-targeted National Surgical Quality Improvement Program database (2016-2019) to identify patients who had undergone EVAR for both ruptured and nonruptured AAAs. The patients were categorized according to race (White, Black, and Asian). Patients with a history of abdominal aortic surgery or an indication other than AAAs were excluded. The data was analyzed using the χ2 and Kruskal-Wallis tests, presented as frequencies and percentages or median and interquartile range (IQR) for categorical and continuous variables, respectively. RESULTS: We identified 3629 patients (16.6% female), including 3312 White (91.3%), 248 Black (6.8%), and 69 Asian (1.9%) patients. Black patients were more frequently women (27.0%) compared with White patients (15.9%) and were younger (median age, 71 years; IQR, 64-77 years) than White (median age, 73 years; IQR, 67-79 years) and Asian (median age, 76 years; IQR, 67-81 years) patients (P < .001 for both). The incidence of smoking, congestive heart failure, and dialysis dependency was highest for Black patients, and the incidence of obesity was lowest for Asian patients. The AAAs in Black patients extended more frequently beyond the aortic bifurcation (P = .047). In Asian patients, the internal iliac arteries were more involved (P = .040). For Black patients, 29.8% of the EVARs were performed in a nonelective setting compared with 20.2% for the White and 15.9% for the Asian patients (P < .001). The aneurysm diameter, nonruptured symptomatic rate, and rupture rate were similar across the groups (P = .807). The operative time was prolonged for Black (median, 128 minutes; IQR, 96-177 minutes) compared with White (median, 114 minutes; IQR, 84-162 minutes) patients (P < .001). Postoperatively, Black patients were more likely to require blood transfusion (16.5%) and had prolonged length of hospital stay (median, 2 days; IQR, 1-4 days) compared with White (10.0%; median, 1 day; IQR, 1-3 days) and Asian (4.3%; median, 1 day; IQR, 1-3 days) patients (P = .001 and P < .001, respectively). Black patients also had a higher 30-day readmission rate (P = .038). On multivariate analysis, Black race was an independent factor for length of stay >1 day after both elective and nonelective EVAR and 30-day readmission for elective EVAR, but not 30-day mortality after elective and nonelective EVAR. CONCLUSIONS: In the present nationwide sample of EVAR cases, Black patients were more often women and younger. Despite similar rates of symptomatic and ruptured AAAs at presentation and 30-day mortality, Black patients more often presented and were treated during the same nonelective admission; they also had associated increased length of hospital stay and readmission. These findings signal a missed opportunity to diagnose, optimize, and treat this particular group of patients in an elective setting.

Race-based outcomes of thoracic aortic aneurysms and dissections in the Global Registry for Endovascular Aortic Treatment.

OBJECTIVE: This study characterizes racial differences in presentation, as well as short- and long-term outcomes after endovascular treatment of thoracic aortic aneurysm (TAA) and type B aortic dissection (TBAD). METHODS: We queried the Gore Global Registry for Endovascular Aortic Treatment for thoracic endovascular aortic repairs (TEVARs) performed between 2010 and 2016 and followed through 2022. Pathologies represented were descending TAA, complicated TBAD, and uncomplicated TBAD. Using standard statistical tests, we compared overall and pathology-specific demographics, procedural factors, and outcomes among Black and White patients undergoing TEVAR. RESULTS: We identified 438 TEVAR cases, including 236 descending TAA, 121 complicated TBAD, and 74 uncomplicated TBAD. Overall, Black patients were younger and had a higher incidence of renal insufficiency (P = .001), whereas White patients had more chronic obstructive pulmonary disease (P = .003) and cardiac arrhythmias (P = .037). In patients treated for descending TAA, Black patients had increased device- and procedure-related complications (34.3% vs 17.4%; P = .014), conversion to open repair (2.9% vs 0%; P = .011) and type II endoleak (5.7% vs 1.0%; P = .040), but no differences in mortality, length of hospital stay, or major adverse cardiovascular events. Whereas outcomes of TEVAR for uncomplicated TBAD were comparable, Black patients more frequently presented with complicated TBAD than White patients (Black, 40.5% vs White, 24.8%; P = .008) and had subsequently greater reintervention rates (28.1% vs 12.4%; P = .012), all-cause mortality (hazard ratio, 4.28; 95% confidence interval, 1.74-10.5; P = .002) and aortic-related mortality (hazard ratio, 16.7; 95% confidence interval, 1.49-186; P = .022). CONCLUSIONS: Despite increased device- and procedure-related complications, similar short- and long-term outcomes are achieved in Black and White patients undergoing TEVAR for descending TAA and uncomplicated TBAD. However, Black patients are more likely to present with, require reintervention for, and suffer mortality from complicated TBAD.

Utility of Closed Suction Drains in Groin Incisions after Femoral Artery Exposure.

BACKGROUND: Surgical groin wounds are at risk of delayed healing and infection, leading to costly and prolonged postoperative recoveries. This study assesses the use of closed suction drains (CSDs) as a wound care adjunct in groin incisions to prevent surgical site infections (SSI). METHODS: A single-center retrospective review was performed on 210 consecutive patients after vascular surgery with common femoral artery exposure from 2016 to 2021. The cohort was divided into 2 groups, groins with and without CSD, looking for surgical site complications. A subgroup analysis comparing postoperative outcomes between complicated and uncomplicated groin incisions within both groups was also performed. RESULTS: Of 293 surgical groins, 20% (n = 59) had drains. Overall, the CSD group had higher SSI rates (14% vs. 5.6%), but also had higher proportion of smokers (92% vs. 83%; P = 0.019), diabetes (56% vs. 36%; P = 0.005), coronary artery disease (69% vs. 46%; P = 0.001), hyperlipidemia (69% vs. 51%; P = 0.01), and previous groin surgery (54% vs. 17%; P < 0.001). The higher risk of SSI was not significant after adjustment of these confounders. A separate analysis within each group showed SSI groins with CSD had lower reintervention rates (37.5%) than those without CSD (69%), as well as shorter length of hospital stay (7 [5-11] vs. 22 [7-25] days). CONCLUSIONS: Our study suggests that CSDs can be a beneficial adjunct for groin wounds after common femoral artery exposure in patients with comorbidities cited above. CSDs decrease the risk of reintervention and length of hospital stay.

Effect of Body Mass Index on Early Outcomes of Endovascular Abdominal Aortic Aneurysm Repair.

BACKGROUND: This study compares the presentation, management, and outcomes of patients undergoing endovascular abdominal aortic aneurysm repair (EVAR), based on their weight status as defined by their body mass index (BMI). METHODS: Patients with primary EVAR for ruptured and intact abdominal aortic aneurysm (AAA) were identified in the National Surgical Quality Improvement Program database (2016-2019). Patients were categorized by weight status (underweight: BMI < 18.5 kg/m2, normal weight: 18.5-24.9 kg/m2, overweight: 25-29.9 kg/m2, Obese I: 30-34.9 kg/m2, Obese II: 35-39.9 kg/m2, Obese III: > 40 kg/m2). Preoperative characteristics and 30-day outcomes were compared. RESULTS: Of 3,941 patients, 4.8% were underweight, 24.1% normal weight, 37.6% overweight, and 22.5% with Obese I, 7.8% Obese II, and 3.3% Obese III status. Underweight patients presented with larger (6.0 [5.4-7.2] cm) and more frequently ruptured (25.0%) aneurysms than normal weight patients (5.5 [5.1-6.2] cm and 4.3%, P < 0.001 for both). Pooled 30-day mortality was worse for underweight (8.5%) compared to all other weight status (1.1-3.0%, P < 0.001), but risk-adjusted analysis demonstrated that aneurysm rupture (odds ratio [OR] 15.9, 95% confidence interval [CI] 8.98-28.0) and not underweight status (OR 1.75, 95% CI 0.73-4.18) accounted for increased mortality in this population. Obese III status was associated with prolonged operative time and respiratory complications after ruptured AAA, but not 30-day mortality (OR 0.82, 95% CI 0.25-2.62). CONCLUSIONS: Patients at either extreme of the BMI range had the worst outcomes after EVAR. Underweight patients represented only 4.8% of all EVARs, but 21% of mortalities, largely attributed to higher incidence of ruptured AAA at presentation. Severe obesity, on the other hand, was associated with prolonged operative time and respiratory complications after EVAR for ruptured AAA. BMI, as an independent factor, was however not predictive of mortality for EVAR.

Primary aortoenteric fistula after intravesical instillation of Bacillus Calmette-Guérin for bladder cancer.

OBJECTIVE: Primary aortoenteric fistulas (PAEFs) are a rare entity with high morbidity, and their relationship with Bacillus Instillation of Calmette-Guérin is anecdotal. METHODS/RESULTS: We present a 68-year-old male with a primary aortoenteric fistula after instillation of Bacillus Calmette-Guérin (BCG) for a non-muscle-invasive bladder cancer. Diagnosis was made by CT angiography, subsequently confirmed by intraoperative findings and results of anatomopathological studies of aortic wall samples. We performed an in-situ reconstruction with a silver prosthesis impregnated in rifampicin with satisfactory evolution at one year. CONCLUSIONS: Primary aortoenteric fistula is an extremely rare complication, and although its relationship with intravesical BCG therapy is anecdotal, it should be considered in patients with gastrointestinal bleeding who have previously undergone this treatment. Its diagnosis requires clinical suspicion, and its treatment should be carried out without delay. Long-term targeted anti-biotherapeutic treatment is a fundamental pillar for its management. Reconstruction with an antibiotic-impregnated silver prosthesis is a valid option in cases of controlled infection.

Outcomes and role of shunting during carotid endarterectomy for symptomatic patients.

OBJECTIVE: Shunt placement during carotid endarterectomy (CEA) has often been advocated to protect the ischemic penumbra in patients with symptomatic carotid stenosis. In the present study, we assessed the effect of shunt placement during CEA on postoperative stroke risk in symptomatic patients. METHODS: We queried the American College of Surgeons National Surgical Quality Improvement Program database (2016-2019) for CEA cases with complete CEA procedure-targeted data available. Symptomatic patients were identified as those with a preoperative diagnosis of stroke on presentation (DS), transient ischemic attack, amaurosis fugax, or temporary monocular blindness. The DS patients were further analyzed according to the severity of their stroke using the modified Rankin scale scores. To better assess the effect of shunt placement on the stroke rate, we compared cases of CEA with the patch angioplasty technique stratified by the use of an intraoperative shunt. Patients who had undergone carotid eversion or primary closure were excluded. The baseline demographics and perioperative outcomes were compared using the χ2 and Mann-Whitney U tests. Multivariate analysis was performed to identify the independent risk factors for postoperative stroke and cranial nerve injury. RESULTS: We identified 4652 cases of CEA with patch angioplasty in symptomatic patients, including 1889 with (40.6%) and 2763 without (59.4%) shunt placement. The distribution of age, race, and sex was similar for both procedures. Compared with patients without a shunt, those with a shunt had significantly higher rates of emergency surgery (9.1% vs 7.0%; P = .010), nonelective surgery (40.3% vs 37.2%; P = .035), general anesthesia (97.0% vs 86.3%; P < .001), and bleeding disorders (27.2% vs 22.7%; P < .001). The 30-day incidence of postoperative stroke was similar between the patients with (3.2%) and without (2.6%) shunt placement (P = .219). Additionally, a subgroup analysis failed to show any benefit from shunt placement on the incidence of postoperative stroke, regardless of the preoperative symptoms or neurologic disability. In contrast, shunt placement was associated with an increased rate of cranial nerve injury (4.1% vs 2.4%; P = .001). Multivariate analysis revealed that nonelective surgery (odds ratio [OR], 1.99; 95% confidence interval [CI], 1.36-2.91; P < .001) and DS (vs transient ischemic attack, amaurosis fugax, or temporary monocular blindness; OR, 1.64; 95% CI, 1.12-2.41; P = .012) were predictive of 30-day postoperative stroke. After adjusting for confounders, shunt placement had no effect on stroke risk at 30 days but remained an independent risk factor for cranial nerve injury (adjusted OR, 1.87; 95% CI, 1.32-2.64; P < .001). CONCLUSIONS: For symptomatic patients undergoing CEA with patch angioplasty, shunt placement was associated with an increased risk of cranial nerve injury without a reduction in postoperative stroke risk.

Establishing and maintaining a remote vascular surgery aortic program: A single-center 5-year experience at the Veterans Affairs.

OBJECTIVE: We sought to detail the process of establishing a surgical aortic telehealth program and report the outcomes of a 5-year experience. METHODS: A telehealth program was established between two regional Veterans Affairs hospitals, one of which was without a comprehensive aortic surgical program, until such a program was established at the referring institution. A retrospective review was performed of all patients who underwent aortic surgery from 2014 to 2019. The operative data, demographics, perioperative complications, and follow-up data were reviewed. RESULTS: From 2014 to 2019, 109 patients underwent aortic surgery for occlusive and aneurysmal disease. Preoperative evaluation and postoperative follow-up were done remotely via telehealth. The median age of the patients was 68 years, 107 were men (98.2%), 28 (25.7%) underwent open aortic repair, and 81 (74.3%) underwent endovascular repair. Of the 109 patients, 101 (92.7%) had a median follow-up of 24.3 months, 5 (4.6%) were lost to follow-up or were noncompliant, 2 (1.8%) were noncompliant with their follow-up imaging studies but responded to telephone interviews, and 1 (0.9%) moved to another state. At the 30-day follow-up, eight patients (7.3%) required readmission. Four complications were managed locally, and four patients (3.6%) required transfer back to the operative hospital for additional care. CONCLUSIONS: Telehealth is a great tool to provide perioperative care and long-term follow-up for patients with aortic pathologies in remote locations. Most postoperative care and complications can be managed remotely, and patient compliance for long-term follow-up is high.

COVID-19-related thrombotic complications experience before and during delta wave.

OBJECTIVE: Hypercoagulability and thrombotic complications seen in patients with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), as well as the associated pathophysiology, have been reported extensively. However, there is limited information regarding the factors related to this phenomenon and its association with the Coronavirus disease 2019 (COVID-19) Delta variant. METHODS: A retrospective review including patients admitted to a tertiary center with a COVID-19 positive test and at least one acute thrombotic event confirmed by imaging between June 2020 and August 2021 was performed. We compared the rates of thrombotic events in patients with COVID-19 before and during the Delta peak. We also analyzed the association of the thrombotic complications with demographic characteristics, comorbidities, anticoagulation strategies, and prothrombotic markers while describing other complications secondary to COVID-19 infection. RESULTS: Of 964 patients admitted with COVID-19 diagnosis, 26.5% (n = 256) had a thrombotic event evidenced by ultrasound or computed tomography scan. Venous thromboembolism was found in 60% (n = 153), arterial thrombosis in 23% (n = 60), and both venous and arterial thromboses in 17% (n = 17) of the study cohort. Of all patients, 94% were not vaccinated. Delta variant wave (DW) patients had thrombotic episodes in 34.7% (n = 50/144) of cases compared with 25% (n = 206/820) of non-Delta wave (NDW) patients, posing an estimated risk 1.36 times higher in patients infected with COVID-19 during the DW than NDW. Overall, DW subjects were significantly younger (P < .001) with lower body mass index (P = .021) compared with NDW patients. Statistical analyses showed African American patients were more likely to have arterial thrombosis compared with the other groups when testing positive for COVID-19 (odds ratio [OR], 1.78; 95% confidence interval [CI], 1.04-3.05; P = .035, whereas immunosuppressed patients had less risk of arterial thrombosis (OR, 0.38; 95% CI, 0.15-0.96; P = .042). Female gender (OR, 2.15; 95% CI, 1.20-3.85; P = .009) and patients with active malignancy (OR, 5.99; 95% CI, 2.14-16.78; P = .001) had an increased risk of having multiple thrombotic events at different locations secondary to COVID-19. CONCLUSIONS: COVID-19 infection is associated with elevated rates of thrombotic complications and an especially higher risk in patients infected during the Delta variant peak. We highlight the importance of vaccination and the development of new anticoagulation strategies for patients with COVID-19 with additional hypercoagulable risk factors to prevent thrombotic complications caused by this disease.

Traumatic Lower Extremity Vascular Injuries and Limb Salvage in a Civilian Urban Trauma Center.

BACKGROUND: Data on management of traumatic lower extreity arterial injuries comes largely from military experience and involves few civilian centers. This study reports on the experience of an urban trauma center and factors associated with limb loss. METHODS: A retrospective review of lower extremity arterial injuries between 2013 and 2020 at an academic urban level 1 trauma center was completed. Patients with lower extremity revascularization were included in the final data analysis. Demographics, clinical variables, operative details, type of revascularization, as well as 30-day morbidity and postoperative outcomes were analyzed. The primary outcome of interest was 30-day limb loss. Secondary outcomes included postoperative complications and functional outcomes. RESULTS: Seventy-five patients were included in our analysis. Sixty-nine were male (92%), mean age 33 ± 15 years, 50 patients had penetrating trauma (67%), mean injury severity score was 15 ± 9. Thirty-day limb loss was reported in 8 (11%). Factors associated with limb loss included female sex (P = 0.001), high body mass index (P = 0.001), blunt injury (P = 0.001), associated fractures (P = 0.005), significant soft tissue injury (P = 0.007), delayed repair after shunt placement (P = 0.003), bypass revascularization (P = 0.001), initial revascularization failure (P = 0.019), and wound complications (P < 0.001). Fifty-five patients had at least one return to the operating room (ROR), including 24 patients (32%) for complications related to their revascularization. These included delayed compartment syndrome (n = 7), revascularization failure (n = 9), bleeding (n = 3), and vascular surgical wound complications (n = 5). Mean length of hospital stay (LOS) for the cohort was 24 ± 20 days with 3 ± 3 ROR, in contrast patients who ultimately required amputation had LOS of 57 ± 21 days with 8 ± 4 ROR. Fifty-seven patients (76%) followed in clinic for a median 36 [14-110] days, with only 32 (43%) at >30 days. Twenty-three reported ambulation without assistance, 9 neuromotor deficit including 1 patient that had delayed amputation. CONCLUSION: Patients with blunt trauma and associated fracture and/or extensive soft tissue injury are at risk of limb loss. These injuries are often associated with postoperative wound complications, requiring aggressive soft tissue care that substantially increases ROR and LOS; Expectations for limb salvage in these patients should be tempered when the other associated factors with limb loss mentioned above are also present. When limb salvage is achieved, regaining full limb function remains a challenge.

Percutaneous endovascular abdominal aortic aneurysm repair with monitored anesthesia care decreases operative time but not pulmonary complications.

OBJECTIVES: To report our experience and compare the results of percutaneous endovascular aortic aneurysm repair (PEVAR) performed under monitored anesthesia care (MAC) to PEVAR under general anesthesia (GA). METHODS: A retrospective review of patients who underwent non-emergency endovascular abdominal aortic aneurysm repair (EVAR) was completed. Patients were excluded if they had a complex repair, including fenestrated, branched, or parallel endografting. Demographics, operative data, 30-day mortality/morbidity and postoperative outcomes were analyzed. RESULTS: A total of 159 patients were identified with a median age of 69. 115 patients had PEVAR, 45 (39.1%) PEVAR MAC and 70 (60.9%) PEVAR GA. PEVAR MAC compared to PEVAR GA had decreased operative time (106 vs. 134 min, P < 0.001), time in the operating room (163 vs. 245 min, P = 0.016), and estimated blood loss (EBL) (115 vs. 176 mL P = 0.012). There was no statistically significant difference in the hospital length of stay (LOS) (1.9 vs. 2.7 days, P = 0.133), and post-operative complications including pulmonary (2.2 vs. 2.9%, P = 0.835). Forty-four patients had EVAR with a femoral cutdown (FC), including 14 PEVAR conversions. PEVAR conversion was associated with higher EBL (543 vs. 323 mL, P = 0.03), operative time (230 vs. 178 min, P = 0.01), and operating room time (307 vs. 275 min, P = 0.01) compared to planned EVAR with FC. CONCLUSIONS: PEVAR under MAC is associated with shorter time in the operating room compared to PEVAR under GA. PEVAR under MAC does however not decrease overall morbidities, including postoperative pulmonary complications.

Results of the Galician registry in the treatment of complex aortoiliac aneurysms with GORE® EXCLUDER® Iliac Branch Endoprosthesis (GALIBER).

OBJECTIVE: The objective of this study is to report the medium-term results of GORE® EXCLUDER® Iliac Branch Endoprosthesis (IBE, W. L. Gore & Associates, Flagstaff, Ariz) for the treatment of aortoiliac aneurysms by using the GALIBER registry. METHODS: Patients with aortoiliac or isolated common iliac/hypogastric aneurysms treated with Iliac Branch Endoprosthesis device between January 2014 and May 2019 were prospectively collected from 5 centers. Demographic, clinical, and radiologic data were extracted from electronic databases. Technical success was defined as successful implantation of the Iliac Branch Endoprosthesis device with exclusion of aortoiliac aneurysm, as well as patency of Iliac Branch Endoprosthesis in the follow-up. Iliac Branch Endoprosthesis patency was evaluated by Doppler ultrasound and/or computed tomography based on the protocol of each participant center. Follow-up was 731 days +/- 499. RESULTS: Between January 2014 and May 2019, 105 iliac arteries were treated with GORE® IBE device, in 81 patients (79 men, two women; mean age 71, range 52-91). Only seven patients (8.6%) were symptomatic. 60 patients (74%) had aortic and iliac enlargement. Thirty-three patients presented bilateral iliac aneurysms (40.7%): In twenty-four (29.6%) patients, an Iliac Branch Endoprosthesis device was implanted in both sides, and in nine patients (11.1%), one Iliac Branch Endoprosthesis was used with the embolization of the contralateral hypogastric artery. Technical success was achieved in the 99% (104/105 iliac branch device implanted). There were no procedural deaths or type I or III intraoperative endoleaks observed. During the follow-up (range 55-1789 days), 28 (34.5%) type II endoleaks were observed and one (1.2%) type Ia was observed. The patency of the hypogastric arteries treated with the iliac branch device was 98.1% during the follow-up (range 55-1789 days). In 30% of the patients with contralateral hypogastric embolization, some kind of complications was observed in the embolizated side: one developed ischemic colitis and two buttock claudication. CONCLUSIONS: Preservation of internal iliac artery with the Iliac Branch Endoprosthesis device can be performed safely with excellent technical success and good medium-term patency rates. These results support hypogastric preservation whenever possible to prevent ischemic complications.

A Comparative Analysis Applied to the Partial Discharges Identification in Dry-Type Transformers by Hall and Acoustic Emission Sensors.

Dry-type insulated transformers stand out for their higher applicability in substations, high-voltage instrumentation systems, and electrical installations. In this machine, the insulation system is constituted of dielectric materials such as epoxy resin and Nomex paper. Some critical issues in the operation of this equipment, such as overload, moisture, or heat, can induce a slow degradation of the physical-chemical properties of the dielectric materials, which can culminate in the total failure of the transformer. However, before the transformer's shutdown, it is common to detect discharge activity in the insulation system. Based on this issue, this work proposes an experimental and comparative analysis between acoustic emission and Hall-effect sensors, aiming at differentiating discharges in epoxy resin and Nomex paper, materials that constitute the insulation of the dry-type insulated transformers. Two signal processing techniques were studied: traditional frequency analysis and discrete wavelet transform. The objective is to develop signal processing techniques to differentiate each type of discharge since different discharges require different maintenance actions. The results obtained indicate that acoustic emission sensors and Hall sensors are promising in differentiating discharge in epoxy resin and Nomex paper. Furthermore, the pattern recognition tools presented by this work, which associated the wavelet levels energies and the energy of the full signals with the average band and the equivalent bandwidth, were effective to perform feature extraction of power transformer condition.

Design and validation of an electrophysiological based tool to assess chronic stress. Case study: burnout syndrome in caregivers.

Caregiver burnout syndrome is an increasingly seen condition, although the subjective nature of self-administered psychometric tests and the lack of a consensual diagnostic tool might hinder a proper diagnosis. The availability of objective psychosomatic measures of stress might facilitate the early diagnosis and clinical management of these patients. For this reason, the aim of this work was to develop a quantitative tool to evaluate the stress level of caregivers in a noninvasive and repeatable manner. An observational, controlled, matched study was designed including a group of 38 principal caregivers of chronic patients and a control group of 38 non-caregivers. Psychometric, biochemical, and electrophysiological data were analyzed along with sociodemographic data. A quantitative chronic stress reference scale (CSRs) was constructed based on the weighted contribution of several psychometric and biochemical variables and afterwards, a predictive psychosomatic model (ESBSm) correlated with CSRs was elaborated from extracted variables of several electrophysiological signals monitored for 10 min. The resulting CSR scale shows a high power to discriminate caregivers from the control group while the ESBSm shows a 79% correlation with the CSR scale validated through a 5-fold process. Therefore, the results demonstrate that the ESBS model is an objective and validated tool to diagnose the degree of stress linked to burnout in caregivers of chronic patients from a 10-min session of noninvasive monitoring with a reliability equivalent to the questionnaires currently used to quantify stress in caregivers.

Application of the Gaussian Mixture Model to Classify Stages of Electrical Tree Growth in Epoxy Resin.

In high-voltage (HV) insulation, electrical trees are an important degradation phenomenon strongly linked to partial discharge (PD) activity. Their initiation and development have attracted the attention of the research community and better understanding and characterization of the phenomenon are needed. They are very damaging and develop through the insulation material forming a discharge conduction path. Therefore, it is important to adequately measure and characterize tree growth before it can lead to complete failure of the system. In this paper, the Gaussian mixture model (GMM) has been applied to cluster and classify the different growth stages of electrical trees in epoxy resin insulation. First, tree growth experiments were conducted, and PD data captured from the initial to breakdown stage of the tree growth in epoxy resin insulation. Second, the GMM was applied to categorize the different electrical tree stages into clusters. The results show that PD dynamics vary with different stress voltages and tree growth stages. The electrical tree patterns with shorter breakdown times had identical clusters throughout the degradation stages. The breakdown time can be a key factor in determining the degradation levels of PD patterns emanating from trees in epoxy resin. This is important in order to determine the severity of electrical treeing degradation, and, therefore, to perform efficient asset management. The novelty of the work presented in this paper is that for the first time the GMM has been applied for electrical tree growth classification and the optimal values for the hyperparameters, i.e., the number of clusters and the appropriate covariance structure, have been determined for the different electrical tree clusters.

A New Acoustic-Based Approach for Assessing Induced Adulteration in Bovine Milk.

Milk is an important dietary requirement for many populations due to its high nutritional value. However, increased demand has also made it prone to fraudulent activity. In this sense, scientists have sought to develop simple, low-cost, and portable techniques to achieve quality control of milk in industry and farms as well. This work proposes a new instrumentation system based on acoustic propagation and advanced signal processing techniques to identify milk adulteration by industrial contaminants. A pair of transmitter-receiver low-cost piezoelectric transducers, configured in a pitch-catch mode, propagated acoustic waves in the bovine milk samples contaminated with 0.5% of sodium bicarbonate, urea, and hydrogen peroxide. Signal processing approaches such as chromatic technique and statistical indexes like the correlation coefficient, Euclidian norm and cross-correlation square difference were applied to identify the contaminants. According to the presented results, CCSD and RMSD metrics presented more effectiveness to perform the identification of milk contaminants. However, CCSD was 2.28 × 105 more sensitivity to distinguish adulteration in relation to RMSD. For chromatic clustering technique, the major selectivity was observed between the contamination performed by sodium bicarbonate and urea. Therefore, results indicate that the proposed approach can be an effective and quick alternative to assess the milk condition and classify its contaminants.

Staged Treatment for an Unusual Case of Median Arcuate Ligament Syndrome Caused by Compression of the Celiac and Superior Mesenteric Arteries.

We report the unusual presentation of a patient with median arcuate ligament syndrome (MALS) and compression of both the celiac artery and the superior mesenteric artery (SMA). He underwent a staged treatment. First, a laparoscopic release of the median arcuate ligament was performed. In the second stage, due to persistent postprandial pain, the SMA was stented, resulting in complete symptom relief. Recognizing this rare anatomical presentation is very important to avoiding MALS misdiagnosis and providing the appropriate staged treatment.

Off-label use of Proglide percutaneous closure device in iatrogenic arterial catheterizations: Our experience.

INTRODUCTION: Incidental arterial puncture is one of the main complications associated with central venous catheter placement. Manual compression to achieve hemostasis in subclavian and carotid artery punctures is often ineffective because of the anatomical arterial position. Accidental cannulation has traditionally been treated with open surgery or endovascular treatment, but such procedures are not exempt from complications. OBJECTIVES: Report our experience with ultrasound-guided off-label use of Perclose ProGlide (Abbott Vascular Inc., Santa Clara, CA, USA) in patients with iatrogenic arterial cannulation. METHODS: Six unstable patients with accidental arterial catheterization during placement of a central venous catheter: five of them in the subclavian artery and one in the right common carotid artery. Ultrasound-guided percutaneous closure was performed at bedside using a Perclose ProGlide (Abbott Vascular Inc., Santa Clara, CA, USA). RESULTS: All patients underwent duplex ultrasound 6, 12, 24, and 48 h postprocedure, and no complications associated with percutaneous closure (embolism, ischemia, stenosis, or arterial occlusion, bleeding, pseudoaneurysm, etc.) were described. CONCLUSIONS: Accidental artery puncture during central venous catheterization is an uncommon situation but can be effectively managed by using percutaneous vascular closure device. It is a reliable alternative that should be considered as a first-line approach before endovascular or open surgery, specially in patients with unstable conditions in which it is possible to be performed without transfer to an operation room.

The role of heparin in endovascular repair of blunt thoracic aortic injury.

OBJECTIVE: Early diagnosis and treatment are essential to improve survival of patients with blunt thoracic aortic injury (BTAI). Often, aortic surgical intervention may be delayed because of increased risk of bleeding with heparin, particularly in polytrauma victims. We believe that surgical delay may be remedied by proceeding without heparinization. This study reviewed the outcome of patients subjected to thoracic endovascular aortic repair (TEVAR) under full, low-dose, and no intraoperative systemic heparinization. METHODS: There were 77 cases of confirmed BTAI identified and retrospectively analyzed at a high-volume urban trauma center during a period of 15 years (March 2003-September 2017). Patients were stratified into three groups on the basis of the intraoperative use of heparin during TEVAR, as follows: full heparin (FH), low-dose heparin (LH), and no heparin (NH). Baseline characteristics including the patients' demographics, diagnostic laboratory data and imaging studies, operative reports, postoperative complications, embolic and bleeding outcomes, and mortality data were reviewed. RESULTS: Of the 77 total patients who underwent TEVAR for BTAI, 42 patients received full-dose heparinization, 18 received low-dose heparin, and 17 had no use of systemic heparin. There was no significant difference in age, sex, body mass index, or smoking history. The most common mechanism of injury was motor vehicle collision. Grade 3 (pseudoaneurysm) was the predominant type of BTAI (FH, 69.0%; LH, 61.1%; NH, 76.5%; P = .23). The mean interval between admission and repair was three times longer in the FH group than in the NH group (FH, 2.33 days; NH, 0.76 day; P = .091). The mean time in the intensive care unit was shorter in the NH group vs the FH group (15 days vs 26.21 days; P = .025). Thromboembolic and bleeding outcomes and mortality rates were comparable in all three groups; 57 patients continued follow-up for a mean time of 30.99 months. CONCLUSIONS: Our study shows no statistically significant difference in outcomes between the heparinized and nonheparinized groups. The primary benefit of the NH group is seen in time to repair. Although not statistically significant, the mean time to repair was three times longer in the FH group. Patients in the NH group also benefited from prompt intervention and treatment. Therefore, intraoperative heparinization in critically ill patients with BTAI undergoing TEVAR remains at the surgeon's discretion, although the lack of heparinization appears to be a safe and potentially faster alternative, particularly in the polytrauma patient.

Left subclavian to descending aorta bypass: A less invasive extra-anatomical solution for a type A interrupted aortic arch.

Interrupted aortic arch (IAA) is defined as a discontinuity of the aortic lumen from the aortic arch to the descending aorta. The incidence of this congenital malformation is three per million live births. It represents about 1.5% of congenital cardiac abnormalities. The classification system for IAA is divided into three distinct categories-type A: interruption of the lumen distal to the left subclavian artery, occurring in 43% cases; type B: interruption between the left carotid and left subclavian arteries, occurring in 53% cases (the most common); and type C: interruption between the innominate and left carotid, occurring in 4% cases. We describe the case of a 47-year-old woman who had a symptomatic type A IAA. A single-stage extra-anatomic bypass was performed between the left subclavian and the descending thoracic aorta using a 14 mm Dacron graft. The use of this approach is an option to solve this challenging clinical problem.