Digital Artery Research Articles

VALIDATION AND FEASIBILITY OF AN AUTOMATED SYSTEM FOR THE ASSESSMENT OF VASCULAR STRUCTURE AND MECHANICAL PROPERTIES IN THE DIGITAL ARTERIES THROUGH ULTRA-HIGH FREQUENCY ULTRASOUND

Objective: The validation of a semi-automatic software to quantify vascular structure and mechanical properties of digital arteries acquired using ultra high frequency ultrasound (UHFUS). Design and method: UHFUS 5-second longitudinal scans of digital arteries of 15 patients with vascular diseases and 15 healthy controls were obtained by VevoMD (70 MHz probe, FUJIFILM, VisualSonics, Toronto, Canada) and analyzed using Carotid Studio (Quipu Srl, Pisa, Italy), using as reference technique a manual measurement in a Matlab interface (MathWorks, R2019b). Agreement between the two techniques for diameter, distension and intima-media thickness (IMT) was evaluated using Bland-Altman analyses; inter- and intra-operator reproducibility was carried out using coefficients of variation (CV). Results: No trend or significant bias were observed between Carotid Studio and Matlab manual analysis for diameter, distension, and IMT. All limits of agreement were acceptable. Intra-observer CV of diastolic diameter and IMT were 4.1 %, and 4.2 % respectively. Inter-observer CV for diastolic diameter, and IMT were 7.3 % and 5.4% respectively. Intra- and inter- observer CV for distension were higher (25.7 % and 26.7 % respectively). Conclusions: Carotid Studio software is a valid and reproducible tool for the assessment of vascular structure and mechanical properties in UHFUS scans of digital arteries.

A dorsalis pedis venous flap containing a U-shaped venous arch for the reconstruction of fingertip defects.

In small-area soft tissue defects of the fingers, venous flaps have the advantages of easy design and harvesting, and also a thin and flexible texture. Although the artery-vein-vein (A-V-V) pattern is the safest pattern, the tiny veins in the finger pulp make anastomosis difficult. We have designed a modified blood flow pattern flap using the dorsum of the foot as the donor site and anastomosing the U-shaped blood vessels in the venous flap with the two digital arteries in an artery-vein-artery (A-V-A) pattern to reconstruct the digital arterial arch without the need for venous anastomosis. Our study included 22 patients with 23 fingertip defects. In the 23 fingers, 18 flaps survived completely and four had only partial marginal necrosis. The donor site healed well without significant scar hyperplasia.Level of evidence: IV.

Facilitated harvesting of a radial artery superficial palmar branch flap for reconstruction of moderate finger skin defects

Radial artery superficial palmar branch harvesting is technically challenging, especially for inexperienced hand surgeons. The short pedicle and a damaged recipient digital artery require proximal digital artery dissection and relatively long pedicles. Herein, we describe a facilitated flap elevation technique and its application in various cases. From 2013 to 2021, 10 patients with finger injuries received radial artery superficial palmar flaps. We assessed flap survival, sizes, complications, two-point discrimination, and the Semmes-Weinstein monofilament test results. The main shortcoming of a radial artery superficial palmar flap is its short pedicle. Therefore, we developed a long skin flap design in the long axis direction, and the accompanying vein was dissected proximally to the radial artery to obtain a long pedicle. All flaps survived. The median flap dimension was 5.0×2.2cm (maximum size: 6.0×2.0+5.0×2.0cm [for a bilobed flap]). While nerve reconstruction was performed in one patient, all patients had preserved sensation. A sufficiently long pedicle can be obtained by dissecting the accompanying vein proximally to the radial artery. Perforators found in the skin around the scaphoid tubercle in all cases suggest value in including this region in flap design. To obtain a longer pedicle, the flap was developed with the long-skin design in the long-axis direction. Although the accompanying vein is usually thin and difficult to anastomose with the finger vein, its proximal dissection led to the accompanying vein of the radial artery that facilitated the harvesting of a sufficiently long vein.

Flow-through Dorsoulnar Perforator Flap Repair of Soft-Tissue Defect of the Finger with Segmental Digital Arterial Defect.

The aim of this study was to investigate the feasibility of transferring the free flow-through dorsoulnar perforator flap to reconstruct severely injured fingers. From January 2015 to March 2019, 16 patients, 16 thumb or fingers volar partial defects concomitant with segmental digital arterial defects, were included in this study. The flow-through dorsoulnar perforator flaps were used to repair the finger wounds and reconstruct digit arteries. Sixteen fingers in 16 patients were successfully reconstructed and all flaps survived completely. At the final follow-up, the appearance of the affected fingers was aesthetically pleasing. Two-point discrimination of the fingertips was 7.5-11.0 mm. According to the Total Active Motion (TAM) method: nine fingers were excellent, four were good, and three were fair. The free flow-through dorsoulnar perforator flap can achieve the goal of mending finger soft-tissue conditions complicated with segmental digital arterial defects with good results. Key Words: Flow-through flaps, Perforator flap, Dorsoulnar artery, Soft-tissue defect.

The Bridged Digital Artery Perforator Flap as an Alternative Reconstructive Option for Dorsal Digital or Toe Soft Tissue Defects.

Dorsal digital soft tissue defects are considered among the most challenging to reconstruct. Numerous treatment options are proposed, including advancement flaps, antegrade, retrograde flow flaps, adipofascial flaps, and digital artery perforator flaps. However, the optimal treatment remains controversial. The concept of the "bridge principle," consisting of the indirect transfer of the flap to the defect area through a muscular bridge, has recently introduced by authors for medial canthal reconstruction. The aim of the study was to examine the feasibility of its application in digital reconstruction for dorsal defects and the development of a new flap. The utilization of the dorsal subcutaneous adipofascial digital or toe tissue as a "bridge" led to description and development of bridged digital artery perforator flaps as an alternative treatment of such defects. From November 2017 to September 2019, a series of 14 patients (mean age of 57.1 years) suffered from dorsal digital or toe soft tissue defects of different dimensions and sustained reconstruction with this new technique. Twelve digits and 2 toes have been concerned. The mean size of the defects was 1.3 × 1.1 cm. All flaps survived without a sign of venous congestion. No functional digital or toe problems were observed during the follow-up period (mean of 11.6 months). Minor wound dehiscence presented in 2 cases (2 of 14 [14.3%]) and a transient skin swelling around the flap in 1. A new concept was introduced to resolve a challenging problem. Initial outcomes are very encouraging. These flaps could be a valuable and reliable reconstructive option.

CT Visualization of Vasculature Channels in Modern and Fossil Sloth Ungual Claws

One of the interesting features of modern sloths is the vasculature patterns of their upper and lower limbs. Even though sloths are endothermic like other mammals, their mean body temperature tends to be lower, more variable, and more linked to the ambient temperature than other placental mammals. Like some other mammals from environments with temperature extremes, they possess rete arteriovenous bundles, which work as an effective heat exchange mechanism, where heat from distally flowing arterial blood is transferred to proximally flowing venous blood. This minimizes the heat loss from the extremities while still maintaining blood flow. The temperature gradient increases in the rete system when the animal’s core temperature decreases, which cools the limbs and preserves core body heat. When the body temperature rises the flow through the superficial venous system increases, which promotes heat loss and body cooling.This begs the question of how this complex vasculature system may or may not extend to the distal phalanges and claws of the sloth, perhaps their most distinctive feature. One possibility could be that to work with the limb cooling function of the rete system, the distal phalanx and claw may be poorly vascularized so as not to increase chances for heat loss. However, considering the extensive and important use of their claws, they may require extensive vascularization to withstand the large amount of stress they are often under. This study uses Micro CT scans of sloth ungual phalanges to visualize their vascular channels. In both modern and extinct giant ground sloths, vascular networks through the bone of the ungual phalanx are quite extensive, and are very clearly linked to externally visible channels and impressions left by the proper digital arteries. In ground sloths these internal vascular channels quickly branch on either side and continue distally, letting off smaller branches as they go. These channels are rather large, even appearing to be artificial drill holes on one specimen that has the distal end broken off. Modern sloths show a similar pattern, but their vascular channels take up proportionally less space in the bone than in the giant ground sloths. This difference may be due extinct giant ground sloths’ more varied use of their claws. These complex patterns show that sloth claws require a significant blood supply, and may indicate that the rete system is effective enough that by the time the arterial blood gets to the distal phalanx it has been sufficiently cooled to not be a significant source of heat loss.

Raynaud’s Phenomenon with Focus on Systemic Sclerosis

Raynaud’s phenomenon is a painful vascular condition in which abnormal vasoconstriction of the digital arteries causes blanching of the skin. The treatment approach can vary depending on the underlying cause of disease. Raynaud’s phenomenon can present as a primary symptom, in which there is no evidence of underlying disease, or secondary to a range of medical conditions or therapies. Systemic sclerosis is one of the most frequent causes of secondary Raynaud’s phenomenon; its appearance may occur long before other signs and symptoms. Timely, accurate identification of secondary Raynaud’s phenomenon may accelerate a final diagnosis and positively alter prognosis. Capillaroscopy is fundamental in the diagnosis and differentiation of primary and secondary Raynaud’s phenomenon. It is helpful in the very early stages of systemic sclerosis, along with its role in disease monitoring. An extensive range of pharmacotherapies with various routes of administration are available for Raynaud’s phenomenon but a standardized therapeutic plan is still lacking. This review provides insight into recent advances in the understanding of Raynaud’s phenomenon pathophysiology, diagnostic methods, and treatment approaches.

Training on skin flap elevation in hand surgery using cadavers embalmed by the saturated salt solution method: effectiveness and usefulness.

Thiel embalmed and fresh-frozen cadavers have been mainly used for hand surgery training. We held a training seminar on skin flap elevation using cadavers embalmed by the saturated salt solution method. This study aimed to evaluate the usefulness of such training and to validate the suitability of saturated salt solution-embalmed cadavers for hand surgery training. Participants were trained in elevation procedures for the oblique triangular, reverse digital artery, reverse radial forearm, and reverse dorsal metacarpal artery flaps. Forty-eight surgeons participated in three seminars (one held in 2017, 2018, and 2019 each). A self-assessment of the participants' confidence levels for their surgical skills was performed before and immediately after the seminar, and the suitability of saturated salt solution-embalmed cadavers was determined in terms of visual perception, tactility, comparison with real-world surgical settings, and usefulness. The confidence level for all skills increased immediately after the seminar. The surgeons reported that the visual perception and tactility of the saturated salt solution-embalmed cadavers were comparable to those of a living body, and the cadavers were rated higher with respect to their usefulness. Hand surgery seminars using cadavers embalmed by the saturated salt solution method are considered useful for training in skin flap techniques.

Preoperative MRI Evaluation of Hand Vessels in Children With Congenital Syndactyly Malformation by a Contrast-Enhanced Three-Dimensional Water-Selective Cartilage Scan.

BackgroundIt is crucial to preoperatively assess the arteries of the hands in congenital syndactyly malformation (CSM) patients because this information can affect the therapeutic outcome and prognosis.ObjectiveTo investigate the value of a contrast-enhanced three-dimensional water-selective cartilage scan for the preoperative evaluation of CSM in children.Materials and MethodsContrast-enhanced three-dimensional water-selective cartilage scan 3.0 T magnetic resonance imaging (MRI) performed in 16 clinically diagnosed CSM patients with 17 affected hands. The arteries of the hands were displayed with a focus on the bifurcation position of the common palmar digital arteries (CPDAs) and the maturity of the proper palmar digital arteries (PPDAs). The MRI results were interpreted by consensus between two experienced pediatric radiologists with 10 years of MRI experience each. The MRI findings were compared with the operation results.ResultsOf 51 CPDAs in the 17 affected hands, MRI showed that 30 had an abnormal bifurcation position and 20 had a normal position, and of the 102 PPDAs, 14 were shown to have an abnormal maturity and 85 a normal state, which were confirmed by surgery. The accuracy, sensitivity and specificity for determining the bifurcation position of the CPDAs based on MR maximum intensity projection reconstructed images were 98.04% (50/51), 96.77% (30/31) and 100% (20/20), respectively. The maturity of the PPDAs was judged by MR maximum intensity projection reconstructed images with an accuracy, sensitivity and specificity of 97.06% (99/102), 82.35% (14/17) and 100% (85/85), respectively.ConclusionContrast-enhanced three-dimensional water-selective cartilage scan has excellent performance in displaying the bifurcation position of the CPDAs and the maturity of the PPDAs and is of high value for the preoperative evaluation of CSM in children.

Validation and Feasibility of an Automated System for the Assessment of Vascular Structure and Mechanical Properties in the Digital Arteries: An Ultrahigh-Frequency Ultrasound Study.

Ultrahigh-frequency ultrasound (UHFUS) allows sharp visualization of human small muscular arteries. This may help in elucidating some aspects of the pathophysiology of arterial aging, such as the stiffness gradient between large and small conduit arteries and its consequences on the microcirculation, as well as vascular diseases affecting medium-sized arteries. However, UHFUS use is still limited, partly because of the lack of validated tools to quantify vascular structure and mechanical properties of small muscular arteries. In this validation study, scans of digital arteries were obtained with UHFUS (VevoMD, Visualsonics-Fujifilm, Toronto, ON, Canada), analyzed using Carotid Studio software (Quipu, Pisa, Italy) and compared with the manual measurement. Agreement between the two techniques on measures of diameter, distension and intima-media thickness (IMT) was evaluated using Bland-Altman analyses; inter- and intra-operator reproducibility was evaluated using coefficients of variation (CVs). Overall, no trend or significant bias was observed between Carotid Studio and manual analysis. All limits of agreement were acceptable. The intra-observer CV of diastolic diameter and IMT were 4.1% and 4.2%, respectively. The inter-observer CV for diastolic diameter and IMT were 7.3% and 5.4%, respectively. Intra- and inter-observer CVs for distension were higher (25.7% and 26.7%, respectively). These results suggest that the Carotid Studio software is a valid and reproducible tool to study UHFUS scans of digital arteries, with potential utility both in rare vascular diseases of medium-sized arteries and in the study of the pathophysiology of arterial aging in general.

An AnteOwl WR intravascular ultrasound-guided parallel wiring technique for chronic total occlusion of below-the-knee arteries

BackgroundAlthough endovascular therapy is used to treat chronic limb-threatening ischemia, long chronic total occlusion (CTO) is still challenging to treat. Especially in patients with poor run-off below-the-knee (BTK) arteries, it is difficult to perform a retrograde approach, and even guidewire passage may be difficult.Case presentationWe treated two cases of chronic limb-threatening ischemia using our novel extreme antegrade guidewire crossing technique by AnteOwl WR intravascular ultrasound (IVUS)-guided parallel wiring to a BTK artery (EXCAVATOR technique). Case 1 was a 70-year-old man with ulceration of the right toe. The AnteOwl WR IVUS was intentionally advanced into the subintimal space of the posterior tibial artery, and the totally intraplaque route was advanced by IVUS-guided parallel wiring that was successfully passed from the lateral plantar aspect to the true lumen of the digital artery. Case 2 was a 76-year-old woman with rest pain and cyanosis of the right lower limb. Angiography showed total occlusion from the superficial femoral artery to BTK arteries. AnteOwl WR IVUS-guided parallel wiring was repeatedly performed until the distal true lumen of the peroneal artery was reached, and revascularization was successfully achieved via the antegrade approach alone.ConclusionsWith its excellent crossable performance, good image quality, and high navigational ability within the CTO, the AnteOwl WR can be used to pass parallel wiring into the distal true lumen for BTK CTO.

Reconstructive Timing of Nail Preserved Fingertip Injury With Reverse Digital Artery Island Flap.

This study aimed to compare the outcomes of reverse digital artery island flap (RDAIF) in primary and secondary reconstruction after failed replantation or composite graft method. This study retrospectively analyzed 42 patients that underwent RDAIF (18 primary and 24 secondary). Preoperative details (demographics, injury details, and waiting days) and postoperative outcomes (active arc of proximal interphalangeal [PIP] and distal interphalangeal (DIP) joints, extension loss of PIP, flexion arc of metacarpophalangeal joint, total active motion, flap sensation, the presence of numbness, Tinel's sign and cold intolerance) were evaluated. Quick Disabilities of the Arm, Shoulder, and Hand score (Quick-DASH) and patient satisfaction were also statistically compared between the 2 groups. There was no significant difference in patient demographics between the 2 groups in sex, age, smoking and diabetic history, affected hand and finger, injury type and level, and flap area. The only difference was in waiting days. Similar sensory recovery and patient satisfaction were found in both groups. Range of motion in the DIP and PIP joints, extension loss of PIP, total active motion, and Quick-DASH were superior in the primary coverage group. Increasing age, subzone III injury, and secondary reconstruction were found to be the factors that adversely affected the postoperative range of motion. Secondary reconstruction was more likely to result in joint contracture. In the event of a damaged fingertip amputation in older patients, primary flap reconstruction should be considered as the initial treatment of choice, with regard to the ultimate range of motion.

Dorsal Digital Artery Island Flap is an Effective Technique for Coverage of Finger Defect

Background: Reconstruction of soft tissue defects in fingers is a challenging problem and continues to evolve. A variety of flaps for reconstructing small-to-moderate defects have been described, but none is beyond drawbacks. The purpose of this study is to report and to evaluate the efficacy of the use of dorsal digital island flaps (DDIF) for the reconstruction of finger defects. Materials and Methods: The study was conducted from January 2020 to September 2021 in the Burn and Plastic Surgery Department at Rajshahi Medical College Hospital. A total of 10 DDIF, based on either proximally or distally, were done in 9 patients. Most of the causes of defects were electrical burns. All flaps survived with minimal complications to the donor finger. Results: Among 10 digits, the mean defect size was 4.24 (±2.34) cm2, ranging from 1.92 to 5.95 cm2. Defects were observed: 4 in middle fingers, 3 in thumb, 2 in ring fingers, and one in index finger. 6 fingers were in right hand. DDIF covered the defects on volar (5 cases), dorsal (4 cases), and both (1 case) surfaces. According to site, one case had defect on proximal phalanx with 3rd web space, 4 instances had on proximal phalanx, defect involving on both proximal and middle phalanx was in one case and rest 4 cases had defect on distal phalanx. Among 10 DDIF, 7 (70%) flaps were survived without any loss. Rest 3 (30%) cases had marginal necrosis (less than 2 mm loss) but did not require further procedure. Conclusion: DDIF is a reliable and effective option for finger defect coverage.

Primary closure using a perforator flap-based technique for the treatment of Dupuytren's contracture

We aim to present a perforator flap-based technique that is useful in the resection and reconstruction of the palmar fascia for the treatment of Dupuytren's contracture with primary closure. A curve incision through the palmar skin radial to the hypothenar area was made. The ulnar side of the palmar skin and the subcutaneous fat was raised to the ulnar side, exposing the palmar fascia. The ulnar palmar digital artery extending from the superficial palmar arch curves distally towards the little finger at a point perpendicular to the fourth interdigital space with parting branches into the subcutaneous fat radial of the flap was carefully identified and preserved, and the Dupuytren's cords were excised. Depending on contracture involvement, additional incision extending from the arc of the palmar incision to the proximal interphalangeal joint is made to raise the digital flap similar to that of the palmar incision. The perforator flap was raised along the hypothenar region in 53 hands of 48 patients, nine women and 39 men, and their age at the time of surgery averaged 56 years. Two patients complained of paresthesia in the ring and little fingers after surgery in 2015, and the symptom had disappeared without further intervention before the latest follow-up in 2017. There was no incidence of skin necrosis, delayed healing, and no recurrence within the follow-up period. This perforator flap-based technique is technically reliable and straightforward with better exposure and easier removal of all the diseased fascia, making it possible for primary healing without skin necrosis and acceptable for the treatment of patients at all stages of the disease.

A Novel Methodology for the Synchronous Collection and Multimodal Visualization of Continuous Neurocardiovascular and Neuromuscular Physiological Data in Adults with Long COVID.

Background: Reports suggest that adults with post-COVID-19 syndrome or long COVID may be affected by orthostatic intolerance syndromes, with autonomic nervous system dysfunction as a possible causal factor of neurocardiovascular instability (NCVI). Long COVID can also manifest as prolonged fatigue, which may be linked to neuromuscular function impairment (NMFI). The current clinical assessment for NCVI monitors neurocardiovascular performance upon the application of orthostatic stressors such as an active (i.e., self-induced) stand or a passive (tilt table) standing test. Lower limb muscle contractions may be important in orthostatic recovery via the skeletal muscle pump. In this study, adults with long COVID were assessed with a protocol that, in addition to the standard NCVI tests, incorporated simultaneous lower limb muscle monitoring for NMFI assessment. Methods: To conduct such an investigation, a wide range of continuous non-invasive biomedical sensing technologies were employed, including digital artery photoplethysmography for the extraction of cardiovascular signals, near-infrared spectroscopy for the extraction of regional tissue oxygenation in brain and muscle, and electromyography for assessment of timed muscle contractions in the lower limbs. Results: With the proposed methodology described and exemplified in this paper, we were able to collect relevant physiological data for the assessment of neurocardiovascular and neuromuscular functioning. We were also able to integrate signals from a variety of instruments in a synchronized fashion and visualize the interactions between different physiological signals during the combined NCVI/NMFI assessment. Multiple counts of evidence were collected, which can capture the dynamics between skeletal muscle contractions and neurocardiovascular responses. Conclusions: The proposed methodology can offer an overview of the functioning of the neurocardiovascular and neuromuscular systems in a combined NCVI/NMFI setup and is capable of conducting comparative studies with signals from multiple participants at any given time in the assessment. This could help clinicians and researchers generate and test hypotheses based on the multimodal inspection of raw data in long COVID and other cohorts.

Successful Endovascular Therapy for Total Occlusion of the Distal Radial and Ulnar Artery with Palmar Artery Lesion in a Patient with Critical Hand Ischemia Associated with Systemic Sclerosis

Vasculopathy of systemic sclerosis (SSc) is known to lead to severe limb ischemia and is often associated with macrovascular diseases. Revascularization of proximal macrovascular lesions that cause limb ischemia in patients with SSc has been recommended; however, it has rarely been reported for lesions below-the-elbow (BTE) involving the palmar artery. A 66-year-old female patient with SSc experienced critical hand ischemia (CHI) with gangrene of the left third finger that failed to respond to conventional pharmacological treatment. Angiography revealed total occlusion of the distal radial and ulnar arteries with a palmar artery lesion. Balloon angioplasty was performed for bilateral occlusive lesions around the wrist, which improved antegrade flow to the digital artery. Endovascular therapy may be a feasible option for BTE lesions involving palmar artery disease, presenting with CHI in SSc, when conventional conservative treatments fail.

Selective Fasciectomy in Dupuytren’s Contracture: An Experience of A Specialized Tertiary Hospital in Bangladesh

Background: Dupuytren’s disease is a benign yet disabling, irreversible, progressive fibroproliferative condition affecting the palm and fingers, leading to flection contracture of metacarpophalangeal (MCP) and proximal interphalangeal (PIP) joints.Objective: To evaluate results of selective fasciectomy to correct the deformity of MCP and PIP joints and observe the complications.Methods: This crosssectional study was done on 30 patients of Dupuytren’s contracture treated by selective fasciectomy, between January 2015 and December 2018, in Department of Orthopaedic Surgery, Bangabandhu Sheikh Mujib Medical University (BSMMU), Dhaka, Bangladesh. Selective fasciectomy was done under brachial plexus block, tourniquet control and loupe magnification. Brunner zigzag incision was used. Indications for surgery was MCP flection contracture more than 30⁰ and any degree of PIP flection contracture. Postoperatively hand was immobilised in extension of MCP and PIP joints for 2 weeks and then active and passive movements were encouraged and intermittent splinting for 10 weeks (only at night in last 6 weeks).Results: Among 30 patients, 24 (80%) patients were male, 6 (20%) were female; mean age was 62 years (56-74 years). 12 (40%) cases were bilateral, ring and little fingers involvement were seen in most cases (92%). Mean MCP correction was 53⁰ and mean PIP correction was 34⁰ (p<0.001). There were 3 digital nerve injuries peroperatively which were repaired/reconstructed and protective sensation regained in repaired nerve area at 1 year and 3 (10%) marginal skin loss postoperatively which healed secondarily. Superficial wound infection developed in 3 (10%) patients which healed on dressing and antibiotics. Complex regional pain syndrome developed in 2 (6.66%) patients which were mild and resolved on conservative management. 3 (10%) patients developed scar sequilae which were mild and resolved on conservative treatment. Radial digital artery injury was observed in 1 (3.33%); however, no ischaemic insult was observed postoperatively. 2 (6.66%) patients developed recurrence of the disease who were more than 70 years old; however, they declined further intervention.Conclusion: Selective fasciectomy is an easy and effective procedure with less complication to correct the deformities and improve the gripstrength significantly in Dupuytren’s contracture patients.International Journal of Human and Health Sciences Vol. 06 No. 01 January’22 Page: 41-46

The Soft-Strain Effect Enabled High-Performance Flexible Pressure Sensor and Its Application in Monitoring Pulse Waves.

Flexible and wearable pressure sensors attached to human skin are effective and convenient in accurate and real-time tracking of various physiological signals for disease diagnosis and health assessment. Conventional flexible pressure sensors are constructed using compressible dielectric or conductive layers, which are electrically sensitive to external mechanical stimulation. However, saturated deformation under large compression significantly restrains the detection range and sensitivity of such sensors. Here, we report a novel type of flexible pressure sensor to overcome the compression saturation of the sensing layer by soft-strain effect, enabling an ultra-high sensitivity of ~636 kPa-1 and a wide detection range from 0.1 kPa to 56 kPa. In addition, the cyclic loading-unloading test reveals the excellent stability of the sensor, which maintains its signal detection after 10,000 cycles of 10 kPa compression. The sensor is capable of monitoring arterial pulse waves from both deep tissue and distal parts, such as digital arteries and dorsal pedal arteries, which can be used for blood pressure estimation by pulse transit time at the same artery branch.

A Study on the Middle Transverse Palmar Arch: Preoperative Ultrasonography in Reverse Digital Artery Island Flap

A Study on the Middle Transverse Palmar Arch: Preoperative Ultrasonography in Reverse Digital Artery Island Flap

Assessing mechanical vibration-altered wall shear stress in digital arteries

The aim of this study is to implement and validate a method for assessing acute vibration-altered Wall Shear Stress (WSS) in the proper volar digital artery of the non-exposed left forefinger when subjecting the right hand to mechanical vibration. These changes of WSS may be involved in Vibration White Finger. Hence, an experimental device was set-up to link a vibration shaker and an ultra-high frequency ultrasound scanner. The Womersley-based WSS was computed by picking up the maximum velocity from pulse Wave Doppler measurements and extracting the artery diameter from B-mode images through an in-house image processing technique. The parameters of the former method were optimised on numerical ultrasound phantoms of cylindrical and lifelike arteries. These phantoms were computed with the FIELD II and FOCUS platforms which mimicked our true ultrasound device. The Womersley-based WSS were compared to full Fluid Structure Interaction (FSI) and rigid wall models built from resonance magnetic images of a volunteer-specific forefinger artery. Our FSI model took into account the artery’s surrounding tissues. The diameter computing procedure led to a bias of 4%. The Womersley-based WSS resulted in misestimating the FSI model by roughly 10% to 20%. No difference was found between the rigid wall computational model and FSI simulations. Regarding the WSS measured on a group of 20 volunteers, the group-averaged basal value was 3 Pa, while the vibration-altered WSS was reduced to 1 Pa, possibly triggering intimal hyperplasia mechanisms and leading to the arterial stenoses encountered in patients suffering from vibration-induced Raynaud’s syndrome.