Information about the central venous pressure is important in evaluating several clinical conditions including cardiac failure and volume overload. The jugular veins serve as a primary route for the indirect estimation of the central venous pressure or waveform. The conventional methods for acquiring the central venous pressure in these veins have been through neck visualization and the insertion of catheters. Even though these procedures are effective if done properly, they have various downsides such as being invasive, inaccurate and time consuming. In this research, a sensor is proposed for the noninvasive detection of central venous waveforms within the jugular veins. The sensor is a reflectance configured probe which utilizes laser based on the photoplethysmography principle. The effectiveness of the sensor was tested in-vitro using a mock circulatory loop and was also tested on a single human subject. The results from the tests indicated a very good sensor response in estimating pressure waveforms.

No description available.

Chronic venous disease (CVD) is a common problem in the western world, causes considerable morbidity and has a substantial impact on the health care system in terms of cost of treatment. Most epidemiological research has focussed on the prevalence of varicose veins and ulceration. As such, evidence on the incidence and risk factors is limited. The aim of this study was to measure the incidence of C2 varicose veins, C3-C6 chronic venous insufficiency (CVI) and venous reflux ≥ 0.5 seconds duration in an adult population, and to investigate risk factors associated with the development of these conditions. The Edinburgh Vein Study was a prospective cohort study in which 1,566 men and women aged 18-64 years randomly sampled from the general population underwent an examination comprising clinical and photographic classification of CVD, duplex scanning of the deep and superficial systems of both legs, and completed a questionnaire on lifestyle and medical history. After a 13 year period, invitations were sent to the 1456 survivors to attend a follow up examination. In total, 880 participated in the follow up study, giving a response rate of 60.4%. The overall incidence of C2 varicose veins was 18.2% (95% CI 15.2-21.6), equivalent to an annual incidence rate of 1.4% (95% CI 1.1-1.7). There were no gender differences (p=0.78). Age was associated with the development of new C2 varicose veins the 13 year incidence rose from 9.8% in those aged 18-34 years to 25.7% in those aged 55-64 years (p<0.001). New cases of C3-C6 CVI developed in 9.2% (95% CI 7.0-11.9) of the study sample over 13 years, an annual incidence rate of 0.7% (95% CI 0.5-0.9). There were no gender differences: the 13 year incidence was 10.7% (95% CI 7.2-15.5) and 8.1% (95% CI 5.7-11.6) in men and women respectively (p=0.32). The incidence increased consistently with age, from 2.1% in those aged under 35 years to 17.1% in those aged over 55 years (p<0.001). Of all C3-C6 conditions, C3 corona phlebectatica had the highest incidence (5.3%, 95% CI 3.7-7.5). C5-C6 venous ulceration had the lowest incidence, affecting only 0.5% (95% CI 0.2-1.6) of the study sample over the 13 years. Overall, 12.7% of participants developed new venous reflux ≥0.5 seconds duration from baseline to follow up. The 13 year incidence of superficial, deep and combined venous reflux was 8.8%, 2.6% and 1.3% respectively. Neither age nor sex were associated with the incidence of venous reflux (p>0.05). The highest incidence of reflux was in the great saphenous vein in the lower third of the thigh (4.2%, 95% CI 2.4-7.1). Venous reflux at baseline was associated with the development of new C2 varicose veins at follow up: the incidence creased linearly in those with no reflux, deep, superficial and combined reflux respectively (p<0.001). Family history of venous disease was a significant risk factor for C2 varicose veins (age and sex-adjusted OR 1.7, 95% CI 1.1-2.7) while obesity was associated with the development of CVI (age and sex adjusted OR 4.5 (95% CI 3.3-6.9). Pregnancy appeared to be associated with the development of varicose veins but the association was not statistically significant due to small numbers. No risk factor was associated with the development of venous reflux. The Edinburgh Vein Study is one of a few cohort studies to report the incidence of C2 varicose veins, C3-C6 CVI and venous reflux ≥0.5 seconds duration, and investigate risk factors associated with these conditions. While the results on incidence are consistent with the limited evidence from other studies, the exact effect of risk factors remains unknown. Genetic studies would help clarify whether CVD is an inherited or acquired condition. For other risk factors, results of this study could be combined with other population-based studies in a meta-analysis. The overall estimate of effect would identify the most important risk factors associated with the development of CVD and venous reflux. Finally the natural history and progression of CVD needs to be assessed. The Edinburgh Vein Follow Up Study has examined this relationship and results will help to identify those most likely to progress to more severe disease and, in turn, those who will benefit most from treatment. Appropriate, clinically proven, effective and cost-effective treatments can then be administered in an attempt to reduce the burden of CVD.

published_or_final_version / abstract / toc / Surgery / Master / Master of Surgery

Thesis (M. S.)--Bioengineering, Georgia Institute of Technology, 2007. / Dr. Elliot Chaikof, Committee Member ; Dr. Ross Milner, Committee Member ; Dr. David Ku, Committee Chair.

Isolated distal deep vein thrombosis (IDDVT) is a condition recently suggested to be a different entity to that of proximal disease. There is currently little evidence defining the clinical importance of detection and treatment. International guidelines vary regarding management advice.An observational cohort study, prospective service evaluation and pilot randomised controlled trial were performed within a United Kingdom ambulatory thrombosis service. This project aimed to describe the burden of disease and explore three poorly researched aspects of IDDVT assessment and management: whole-leg compression ultrasound (CUS) performed by non-physicians within an ambulatory framework as a principal diagnostic modality; clinical presentation data and risk profile in comparison to that of proximal disease; the feasibility of further interventional randomised research and the risk/benefit profile of therapeutic anticoagulation.Within this ambulatory cohort, IDDVT accounted for 49.7% of acute thrombosis and differed significantly to proximal disease regarding provocation and symptomatology at clinical presentation. A negative whole-leg CUS excluded deep vein thrombosis with an adverse event rate (diagnosis of symptomatic venous thromboembolism during the 3 month follow up period) of 0.47% (95% CI 0.08 to 2.62). Future interventional research was proved feasible within an ambulatory setting.The randomised controlled trial conducted within this project is the largest to date comparing therapeutic anticoagulation against conservative strategy for the management of acute IDDVT. Patients allocated to therapeutic anticoagulation had significantly less overall propagation of thrombus (Absolute risk reduction [ARR] 25.7%, 95% Confidence interval 5.9 to 44.3 p<0.01), less short-term symptomatic progression (ARR 16.7%, 95% CI 2.6 to 32.1 p=0.05) and a result trending towards significance for reduction in serious thromboembolic complications (ARR 11.4%, 95% CI -1.5 to 26.7 p=0.11).IDDVT is a condition of equal prevalence to proximal venous thrombosis, which varies significantly regarding risk profile and clinical presentation. Using a single whole leg CUS reported by a non-physician within an emergency department pathway is associated with a low adverse event rate. This contemporary data also suggests that therapeutic anticoagulation is beneficial for reduction of short-term complications in IDDVT. The risk of false positive diagnosis and excess anticoagulation remains.This data can inform and direct future design of adequately powered randomised studies, in order to attempt external validation of these findings.

Oral anticoagulants (OACs) are indicated in the first-line treatment of venous thromboembolism (VTE), which comprises of deep vein thrombosis (DVT) and pulmonary embolism (PE). While contemporary guidelines recommend extended-duration anticoagulation after the first diagnosis of unprovoked VTE, the benefits and harms associated with this approach remain unclear across age groups, especially among older adults. Crucially, contemporary estimates of VTE recurrence have not incorporated all-cause mortality as a competing event, the risk of which increases with age. Therefore, we evaluated and synthesized existing literature on of the risk of all-cause mortality by age following completion of limited-duration anticoagulation for a first episode of unprovoked VTE. In addition, we determined the risk of VTE recurrence after completion of limited-duration OAC therapy by age, with death as a competing outcome using data from a prospective cohort study.

by Liu Kin Hung. / Thesis submitted in: Dec, 1997. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1998. / Includes bibliographical references (leaves 87-95). / Abstract also in Chinese. / Chapter 1 --- Introduction --- p.1 / Chapter 2 --- Literature Review --- p.3 / Chapter 2.1 --- Venous anatomy --- p.3 / Chapter 2.2 --- Arterial anatomy --- p.6 / Chapter 2.3 --- Deep vein thrombosis --- p.8 / Chapter 2.3.1 --- Clinical Examination --- p.11 / Chapter 2.3.2 --- Contrast Venogram --- p.12 / Chapter 2.3.3 --- Color duplex ultrasound --- p.13 / Chapter 2.4 --- Arterial resistance --- p.24 / Chapter 2.5 --- Basis for study --- p.28 / Chapter 3 --- Method --- p.30 / Chapter 3.1 --- Subjects --- p.30 / Chapter 3.2 --- Equipments --- p.30 / Chapter 3.3 --- Procedure --- p.31 / Chapter 3.4 --- Data analysis --- p.38 / Chapter 4 --- Results --- p.40 / Chapter 4.1 --- Arterial resistance changes in different groups --- p.40 / Chapter 4.1.1 --- Symptomatic with no DVT versus asymtomatic with no DVT --- p.40 / Chapter 4.1.2 --- Symptomatic with DVT versus symptomatic with no DVT --- p.43 / Chapter 4.1.3 --- Symptomatic acute DVT versus symptomatic chronic DVT --- p.46 / Chapter 4.1.4 --- Symptomatic proximal-DVT versus symptomatic calf-DVT --- p.49 / Chapter 4.1.5 --- symptomatic occlusive DVT versus symptomatic non- occlusive DVT --- p.52 / Chapter 4.2 --- Diagnosis of DVT by arterial resistance changes --- p.57 / Chapter 4.2.1 --- Detection of presence of symptomatic DVT --- p.57 / Chapter 4.2.2 --- Differentiation of characteristics of symptomatic DVT --- p.60 / Chapter 5 --- Discussion --- p.64 / Chapter 5.1 --- Investigation of arterial resistance changes --- p.64 / Chapter 5.1.1 --- Symptomatic with no DVT versus asymtomatic with no DVT --- p.66 / Chapter 5.1.2 --- Symptomatic with DVT versus symptomatic with no DVT --- p.69 / Chapter 5.1.3 --- Symptomatic acute DVT versus symptomatic chronic DVT --- p.72 / Chapter 5.1.4 --- Symptomatic proximal-DVT versus symptomatic calf-DVT --- p.74 / Chapter 5.1.5 --- symptomatic occlusive DVT versus symptomatic non- occlusive DVT --- p.76 / Chapter 5.2 --- Detection and differentiation of DVT by arterial resistance --- p.80 / Chapter 5.2.1 --- Detection of symptomatic DVT --- p.80 / Chapter 5.2.2 --- Differentiation of occlusive DVT from non-occlusive DVT --- p.82 / Chapter 6 --- Conclusion --- p.85 / Chapter 7 --- References --- p.87

Chronic Venous Insufficiency (CVI) is a disease of the lower limbs that affects millions of people in the United States. It is categorized by constant venous hypertension, which can lead to swelling of the legs, pain, skin changes and ulcers. One of the widely known symptoms that can lead to CVI is varicose veins. The main source of the problem of CVI is incompetent venous valves. The purpose of venous valves is to direct blood through the veins to the heart and prevent retrograde flow to the lower limbs. CVI can be caused by leg injury, pregnancy, genetics, age, and prolonged standing. Current treatments of the disease include compression stocking therapy, ablation, vein stripping, and valve reconstruction. CVI has become such a problem for patients, especially those with secondary incompetence in the deep veins, because the current treatments are used to alleviate the symptoms of the disease but do not treat the source of the problem. One solution that has great potential is to create an implantable venous valve that could restore function of the venous system. In the past many prosthetic venous valves have been made, but none are clinically used because of problems with biocompatiblility, thrombogenicity caused by high shear rates, and longterm functionality that has been hindered by leaflet stiffening. The purpose of this research was to create a venous valve that could overcome these difficulties. This was done by designing the valve out of carbon-infiltrated carbon nanotubes (CI-CNTs). This material has been proven to be thrombo-resistant, biocompatible due to its non-reactive properties, and durable. The valve was designed to be initially open and to close with physiological pressures. The shear rate caused by implantation of the valve was minimized to reduce the likelihood of thrombus formation. FEA and CFD analysis was performed to verify the valve would function under physiological conditions and that shear rates would be in the normal range. The final design was tailored for implantation in the common femoral vein. It had a diameter of 12.7 mm, length of approximately 40 mm, and thickness of 0.3 mm. With a hydrostatic pressure of 20 mmHg it fully closed with a maximum stress of 117 MPa, which is below the ultimate strength of CI-CNTs. The CFD analysis demonstrated the valve would cause a maximum shear rate of 225.1 s

Chronic Venous Insufficiency (CVI) is characterized by chronic venous hypertension from blood pooling in the lower limbs. The resulting symptoms include leg pain, varicose veins, fatigue, venous edema, skin pigmentation, inflammation, induration, and ulceration. Reflux from incompetent venous valves is a factor in up to 94% of individuals with CVI. Current treatments of CVI include compression stockings, drug therapy, vein disabling, venous stenting, and surgical correction with varying rates of success. However, a minimally invasive correction of deep venous reflux does not currently exist. A transcatheter prosthetic venous valve has the potential to be an effective, minimally invasive treatment for deep venous reflux which could treat up to 1.4 million individuals in the United States suffering from venous ulceration and make more than 1.7 billion dollars each year. Previously developed prosthetic venous valves have had problems with competency, patency, thrombogenicity, biocompatibility, and incorrect sizing. To meet the clinical need a prosthetic valve needs to be developed which succeeds where previous valves have failed. This thesis describes the design, analysis, pre-clinical testing, and evaluation of a novel prosthetic venous valve. Design specifications for an effective prosthetic venous valve were created. Verification tests were developed and performed which demonstrated that the valve met every design specification. Finite element and computational fluid dynamics simulations were performed to analyze the valve and calculated a maximum shear rate of 2300 s-1 in the valve during the high forward flow after a Valsalva maneuver. The valve is made of a biocompatible material that has low thrombogenicity, Poly(vinyl-alcohol) cryogel. On the average, the valve allows less than 0.5 mL/min of reflux at low and high retrograde pressures even after 500,000 cycles, indicating that it will reduce the reflux of individuals with venous reflux by more than 99.4%. The valve closes in less than 0.07 seconds and allows the distal pressure to rise to an average of 7% of the equilibrium pressure 30 seconds after a simulated ankle flexion. The valve increases the outflow resistance an average of 2.3 mmHg*min/L which is much less than obstruction levels,≥ 5 mmHg*min/L. The valve can fit in a 16 French catheter and is capable of percutaneous delivery. The base of the valve is 1.5 times the diameter of the vein in which it is to be implanted to help correct orientation upon deployment. Fluid behind the valve’s leaflets is ejected with a forward flow rate of 400 mL/min, suggesting that thrombus formation will not occur at this location. A stented valve remained patent in a porcine blood flow loop for 3 hours. The valve remains competent without buckling in a constricted vein at rest. The valve can expand to fit a vein with a maximum diameter 1.4 times the valve's initial diameter with low risk of tearing or leaflet prolapse. An IACUC protocol for a 12 week study to test the valve in sheep was prepared and approved. A study to evaluate the valve in humans is proposed with endpoints that can be tested for statistical significance and compared with other treatments for CVI. A set of valves which will correct reflux in the majority of common femoral, femoral, and popliteal deep veins is proposed and a sizing guide for surgeons is provided. The minimum distance between prosthetic valves placed in the same vein segment is 13 cm. A comparison of this valve with previously developed prosthetic venous valves and recommendations for work to be performed in the future are given. The valve proposed in this work is the only valve to meet all design specification for an effective prosthetic venous valve, and therefore shows great potential to be a minimally invasive treatment for deep venous reflux.