Tissue mimicking materials and finger phantom design for pulse oximetry.

Pulse oximetry represents a ubiquitous clinical application of optics in modern medicine. Recent studies have raised concerns regarding the potential impact of confounders, such as variable skin pigmentation and perfusion, on blood oxygen saturation measurement accuracy in pulse oximeters. Tissue-mimicking phantom testing offers a low-cost, well-controlled solution for characterizing device performance and studying potential error sources, which may thus reduce the need for costly in vivo trials. The purpose of this study was to develop realistic phantom-based test methods for pulse oximetry. Material optical and mechanical properties were reviewed, selected, and tuned for optimal biological relevance, e.g., oxygenated tissue absorption and scattering, strength, elasticity, hardness, and other parameters representing the human finger's geometry and composition, such as blood vessel size and distribution, and perfusion. Relevant anatomical and physiological properties are summarized and implemented toward the creation of a preliminary finger phantom. To create a preliminary finger phantom, we synthesized a high-compliance silicone matrix with scatterers for embedding flexible tubing and investigated the addition of these scatterers to novel 3D printing resins for optical property control without altering mechanical stability, streamlining the production of phantoms with biologically relevant characteristics. Phantom utility was demonstrated by applying dynamic, pressure waveforms to produce tube volume change and resultant photoplethysmography (PPG) signals. 3D printed phantoms achieved more biologically relevant conditions compared to molded phantoms. These preliminary results indicate that the phantoms show strong potential to be developed into tools for evaluating pulse oximetry performance. Gaps, recommendations, and strategies are presented for continued phantom development.

Skin optical properties in the obese and their relation to body mass index: a review.

SIGNIFICANCE: Obesity is a worldwide epidemic contributing directly to several cardiovascular risk factors including hypertension and type 2 diabetes. Wearable devices are becoming better at quantifying biomarkers relevant for the management of health and fitness. Unfortunately, both anecdotal evidence and recent studies indicate that some wearables have higher levels of error when utilized by populations with darker skin tones and high body mass index (BMI). There is an urgent need for a better evaluation of the limits of wearable health technologies when used by obese individuals. AIMS: (1) To review the current know-how on changes due to obesity in the skin epidermis, dermis, and subcutis that could affect the skin optical properties; (2) for the green wavelength range, to evaluate the difference in absorption and scattering coefficients from the abdominal skin between individuals with and without elevated BMI. The changes include alterations in layer thickness and cell size, as well as significant differences in chromophores and scatterer content, e.g., water, hemoglobin, collagen, and lipids. APPROACH: We have summarized literature pertaining to changes in skin and its components in obesity and report the results of our search using articles published between years 1971 and 2020. A linear model was used to demonstrate the absorption and reduced scattering coefficient of the abdominal skin of individuals with and without elevated BMI in the green wavelength range (530 to 550 nm) that is typically found in most wearables. RESULTS: The general trends indicate a decrease in absorption for both dermis and subcutis and an increase in reduced scattering for both epidermis and dermis. At 544-nm wavelength, a typical wavelength used for photoplethysmography (PPG), the absorption coefficient's relative percentage difference between high and low BMI skin, was 49% in the subcutis, 19% in the dermis, and negligible in the epidermis, whereas the reduced scattering coefficient relative difference was 21%, 29%, and 165% respectively. CONCLUSIONS: These findings suggest that there could be significant errors in the output of optical devices used for monitoring health and fitness if changes due to obesity are not accounted for in their design.

Monte Carlo analysis of optical heart rate sensors in commercial wearables: the effect of skin tone and obesity on the photoplethysmography (PPG) signal.

Commercially available wearable devices have been used for fitness and health management and their demand has increased over the last ten years. These "general wellness" and heart-rate monitoring devices have been cleared by the Food and Drug Administration for over-the-counter use, yet anecdotal and more systematic reports seem to indicate that their error is higher when used by individuals with elevated skin tone and high body mass index (BMI). In this work, we used Monte Carlo modeling of a photoplethysmography (PPG) signal to study the theoretical limits of three different wearable devices (Apple Watch series 5, Fitbit Versa 2 and Polar M600) when used by individuals with a BMI range of 20 to 45 and a Fitzpatrick skin scale 1 to 6. Our work shows that increased BMI and skin tone can induce a relative loss of signal of up to 61.2% in Fitbit versa 2, 32% in Apple S5 and 32.9% in Polar M600 when considering the closest source-detector pair configuration in these devices.

Sources of Inaccuracy in Photoplethysmography for Continuous Cardiovascular Monitoring.

Photoplethysmography (PPG) is a low-cost, noninvasive optical technique that uses change in light transmission with changes in blood volume within tissue to provide information for cardiovascular health and fitness. As remote health and wearable medical devices become more prevalent, PPG devices are being developed as part of wearable systems to monitor parameters such as heart rate (HR) that do not require complex analysis of the PPG waveform. However, complex analyses of the PPG waveform yield valuable clinical information, such as: blood pressure, respiratory information, sympathetic nervous system activity, and heart rate variability. Systems aiming to derive such complex parameters do not always account for realistic sources of noise, as testing is performed within controlled parameter spaces. A wearable monitoring tool to be used beyond fitness and heart rate must account for noise sources originating from individual patient variations (e.g., skin tone, obesity, age, and gender), physiology (e.g., respiration, venous pulsation, body site of measurement, and body temperature), and external perturbations of the device itself (e.g., motion artifact, ambient light, and applied pressure to the skin). Here, we present a comprehensive review of the literature that aims to summarize these noise sources for future PPG device development for use in health monitoring.

Synthetic photoplethysmography (PPG) of the radial artery through parallelized Monte Carlo and its correlation to body mass index (BMI).

Cardiovascular disease is one of the leading causes of death in the United States and obesity significantly increases the risk of cardiovascular disease. The measurement of blood pressure (BP) is critical in monitoring and managing cardiovascular disease hence new wearable devices are being developed to make BP more accessible to physicians and patients. Several wearables utilize photoplethysmography from the wrist vasculature to derive BP assessment although many of these devices are still at the experimental stage. With the ultimate goal of supporting instrument development, we have developed a model of the photoplethysmographic waveform derived from the radial artery at the volar surface of the wrist. To do so we have utilized the relation between vessel biomechanics through Finite Element Method and Monte Carlo light transport model. The model shows similar features to that seen in PPG waveform captured using an off the shelf device. We observe the influence of body mass index on the PPG signal. A degradation the PPG signal of up to 40% in AC to DC signal ratio was thus observed.

Porcine Small Intestinal Submucosa Mitral Valve Material Responses Support Acute Somatic Growth.

Background: Conceptually, a tissue engineered heart valve would be especially appealing in the pediatric setting since small size and somatic growth constraints would be alleviated. In this study, we utilized porcine small intestinal submucosa (PSIS) for valve replacement. Of note, we evaluated the material responses of PSIS and subsequently its acute function and somatic growth potential in the mitral position. Methods and Results: Material and mechanical assessment demonstrated that both fatigued 2ply (∼65 µm) and 4ply (∼110 µm) PSIS specimens exhibited similar failure mechanisms, but at an accelerated rate in the former. Specifically, the fatigued 2ply PSIS samples underwent noticeable fiber pullout and recruitment on the bioscaffold surface, leading to higher yield strength (p < 0.05) and yield strain (p < 0.05) compared to its fatigued 4ply counterparts. Consequently, 2ply PSIS mitral valve constructs were subsequently implanted in juvenile baboons (n = 3). Valve function was longitudinally monitored for 90 days postvalve implantation and was found to be robust in all animals. Histology at 90 days in one of the animals revealed the presence of residual porcine cells, fibrin matrix, and host baboon immune cells but an absence of tissue regeneration. Conclusions: Our findings suggest that the altered structural responses of PSIS, postfatigue, rather than de novo tissue formation, are primarily responsible for the valve's ability to accommodate somatic growth during the acute phase (90 days) following mitral valve replacement. Impact Statement Tissue engineered heart valves (TEHVs) offer the potential of supporting somatic growth. In this study, we investigated a porcine small intestinal submucosa bioscaffold for pediatric mitral heart valve replacement. The novelty of the study lies in identifying material responses under mechanical loading conditions and its effectiveness in being able to function as a TEHV. In addition, the ability of the scaffold valve to support acute somatic growth was evaluated in the Baboon model. The current study contributes toward finding a solution for critical valve diseases in children, whose current prognosis for survival is poor.

[Giant calculus in a diverticulum of the anterior urethra]. / Gran litiasis en un diverticulo de uretra anterior.

A case of lithiasis in a front diverticulum of the urethra in male is presented. The unusual presentation it had together with the lack of frequency was pointed out, commenting briefly the diagnostic methods and ways of treatment.

[Orthotopic bilateral ureterocele]. / Ureterocele bilateral ortotópico.

OBJECTIVE: To describe two additional cases of bilateral orthotopic ureterocele and review the literature. METHODS/RESULTS: Both patients, a 70-year-old male and a 56 year-old female, were diagnosed by IVP. Treatment was by a bilateral transverse "smile" incision, which achieved good functional results. However, one of the patients with a calculus inside both ureteroceles developed unilateral grade II-III vesico-ureteral reflux. CONCLUSIONS: Despite the risk of developing vesicoureteral reflux, the transurethral transverse incision is a good method of treatment in symptomatic bilateral orthotopic ureterocele.

[Congenital urethral diverticulum in adults]. / Divertículo uretral congénito en el adulto.

OBJECTIVE: To report an additional case of congenital urethral diverticulum that was incidentally discovered in an adult patient that presented with prostatic syndrome. METHODS: The clinical features diagnosis and treatment of this urethral anomaly are discussed. RESULTS/CONCLUSIONS: Congenital urethral diverticulum is an uncommon finding that usually requires treatment only if it is large or causes important symptoms. The patient described herein had a small urethral diverticulum that did not require treatment. However, the dome of the diverticulum was ruptured during urethrocystoscopy, thus facilitating drainage.

[Lymphoma and the urogenital system: apropos of a case]. / Linfoma y aparato genitourinario: a propósito de un caso.

Lymphomas constitute a group of malignant lymphoreticular diseases that may affect the adrenal glands and the GU system as a primary condition or, more frequently, as distant invasion. We report on a case of diffuse, histiocytic non-Hodgkin lymphoma that had been in hematologic clinical remission but had recurred with invasion of the right renal parenchyma. Initially, it could not be determined whether it was a primary neoplasm or the result of primary lymphatic spread. The reports published in the literature relative to this condition are reviewed.

[Angiodysplasia of the colon: a presentation of 7 cases]. / Angiodisplasias del colon: presentación de siete casos.

Angiodysplasias of the colon are small vascular lesions that probably affect 25% of the population over 50 years. As a result of selective arteriography the number of diagnoses of lower gastrointestinal hemorrhage (HDB) caused by a colonic angiodysplasia (CA) has increased considerably. Seven new cases of colonic angiodysplasia (6 cecal and 1 rectal) are presented, all diagnosed by arteriography. In 6, treatment was surgical and in one, medical. The postoperative bleeding recurrence was 33.3%.

[Carcinosarcoma with chondromatous differentiation of the bladder]. / Carcinosarcoma con diferenciación condromatoide de vejiga.

We report a case of carcinosarcoma whose most striking feature was its markedly chondroid elements that initially prompted us to suspect a chondrosarcoma. The clinical features and treatment of this rare tumor type are briefly discussed.

[Female urethral diverticulum with lithiasis]. / Litiasis en divertículo uretral femenino. A propósito de un caso.

A case of diverticulum of the female urethra complicated by lithiasis is described. The etiopathogenic aspects, clinical features, diagnostic methods and treatment of this rare condition are discussed.

[Diffuse malignant mesothelioma of the testicular tunica vaginalis. Report of a new case]. / Mesotelioma maligno difuso de la túnica vaginal testicular. Presentación de un nuevo caso.

We present a case of diffuse malignant mesothelioma of the tunica vaginalis testis, a very uncommon tumor site, in a patient who also had a tumor localized to the chest. We could not determine however, whether the testicular neoplasm was a primary tumor or a distant metastasis. We describe this tumor type, its mode of presentation, diagnosis and treatment.

[Cephalad blind-ending bifid ureter. Presentation of 3 new cases]. / Uréter bífido ciego craneal. Presentación de tres nuevos casos.

Three additional cases of cephalad blind-ending ureters are reported herein. These cases had been diagnosed during IVP evaluation for other disorders. Its mode of presentation and diagnosis are briefly discussed and the literature reviewed.

[Inguino-scrotal bladder hernia]. / Hernia vesical inguinoescrotal.

We report on a 61-year-old patient with massive scrotal herniation of the bladder and non-Hodgkin malignant lymphoma. We briefly describe this disease entity and its form of presentation, and discuss its diagnosis and treatment.

[Ureteral endometriosis. Role of endourology and treatment]. / Endometriosis ureteral. Papel de la endourología y tratamiento.

Ureteral endometriosis is remarkable not for its frequency, but for the renal compromise it may cause. Because it is silent, diagnosis is established late. An abdominal ultrasound scan permits early diagnosis of the obstructive uropathy. Currently, ureteral stricture can be treated conservatively. In well selected cases, endourological techniques combined with hormone therapy can be an alternative to open surgery.

[Paratesticular rhabdomyosarcoma: report of a case]. / Rabdomiosarcoma paratesticular: aportación de un caso.

A case of paratesticular rhabdomyosarcoma in a 17-year-old patient is described. The clinical features, diagnostic and therapeutic aspects of this rare tumor type are briefly discussed.

[Fournier's gangrene. Presentation of 5 cases and review of the literature]. / Gangrena de Fournier. Presentación de cinco casos y revisión de la literatura.

Five cases of Fournier's gangrene that had been treated at our department over the last five years are described. The literature is reviewed with special reference to the pathogenic, microbiological and therapeutic aspects of this disease entity. Similarly, we underscore the significant drop in mortality with the availability of antibiotics.