Abstract— Peripheral vascular diseases affect hundreds of millions of people worldwide and are often symptomless and undiagnosed. Early diagnosis is crucial for effective treatment and reducing personal and economic costs, particularly where early treatment is geared towards preventing lower extremity amputation. New diagnostic tools are needed to enable this earlier intervention. We have developed a new low-cost, easy to use, non-invasive hemodynamic monitor, HeMo, to address this large and growing problem. Using a novel combination of impedance tomography and electrical volumetric measurements we can calculate real-time changes in peripheral blood volume. We believe that this work will lead to the availability of a fast, easy to use and cost-effective vascular assessment tool, dramatically shortening the time to diagnosis and subsequently intervention, dramatically improving the prognosis of affected patients. I. INTRODUCTION The lower limbs are susceptible to a variety of peripheral vascular diseases (PVD) including peripheral arterial disease, chronic venous insufficiency, intermittent claudication and deep vein thrombosis. These conditions have a considerable socioeconomic impact due to their high prevalence, cost of investigation, treatment and their impact on quality of life. Complicating matters, PVDs are often undiagnosed with over 60% of patients with peripheral arterial disease and diabetes remaining asymptomatic [1]. Several diagnostic tools currently exist to aid in the diagnosis of PVD. The Ankle-Brachial Index (ABI) is a commonly used tool in this regard. Calculated by dividing systolic blood pressure at the ankle by the higher of the two systolic brachial pressures, the ABI is relatively cheap and simple to administer. An ABI greater that 0.9 is considered normal, between 0.4 and 0.9 mild to moderate PAD and lower than 0.4 severe PAD [2], [3]. However, the ABI has poor sensitivity in patients with ‘thickened arteries’ such as those with diabetes, renal disease and the elderly where the ABI may appear normal [2]. Another noninvasive method, Plethysmography, measures changes in blood flow/volume. Several alternative methods have been used to assess peripheral vascular function including impedance, photo, strain-gauge and air plethysmography. However, these methods require a careful setup by a trained practitioner and considerable time to perform the assessment. These requirements have meant that they have been largely replaced by Duplex Ultrasound [4]. Resrach supported by University of Western Sydney Innovation Fund. P. P. Breen is with The MARCS Institute, University of Western Sydney, Penrith NSW, 2751 (phone: +61-2-4736-0507; fax: +61-2-9772- 6326; e-mail: p.breen@uws.edu.au). G. D. Gargiuo is with The MARCS Institute, University of Western Sydney (e-mail: g.gargiulo@ uws.edu.au). Duplex Ultrasonography is a commonly used non- invasive methods to define anatomy, hemodynamics and lesion morphology and highly sensitive in detecting occlusions and stenosis. It is considered a gold standard in the diagnosis of CVI and revealing sites of reflux and/or obstruction in veins [5]. However, it is time-consuming and requires expensive equipment and a highly trained vascular technician, thus limiting its use. Venography involves the injection of contrast solution into the vein of the foot using a 21-gauge butterfly needle. It has several drawbacks and attendant risks that have reduced its once widespread use. Venography can cause a chemical cellulitis with the potential for the development of tissue necrosis, ulceration, or gangrene. Other complications include postphlebographic thrombosis and syndrome, characterized by pain, tenderness, and erythema around the ankle joint not associated with thrombosis [6]. A variety of Angiography methods exist for the assessment of PAD [7]. Contrast angiography entails the intravascular injection of contrast agent during planar X-ray imaging. Magnetic resonance angiography is a less invasive alternative where intravascular blood is detected by virtue of its movement compared with static surrounding tissues. Contrast-enhanced magnetic resonance angiography relies on the T1 shortening effect of intravenously administered contrast media circulating in the blood. Helical computed tomography angiography requires exposure to ionising radiation and the injection of relatively large volumes of contrast material. Clearly, the cost and invasiveness of these methods means that none are suitable for routine screening. Ambulatory Venous Pressure is measured by introducing into a dorsal foot vein a 21-gauge needle, which is then connected to a pressure transducer. The rise/fall of venous pressure is indicative of the health of the vascular bed. Like venography, ambulatory venous pressure measurement is invasive and not suitable for screening, or for repeated examinations to monitor the results of therapy [6], [8]. Each vascular assessment method has advantages and limitations. ABI is fast and cheap but may misdiagnose those with diabetes and the elderly, both growing high-risk populations. Plethysmography has failed to gain traction over ultrasound imaging methods as they incur similar time and personnel commitment. Duplex ultrasound is the mainstay assessment procedure but due to its time-consuming nature and cost is often reserved for use where the patient is already symptomatic. Angiography, Venography and Ambulatory Venous Pressure measures are excellent but are highly invasive and carry attendant risks. The main motivation behind developing a new peripheral vascular assessment device is the fact that many individuals Hemodynamic Monitor for Rapid, Cost-Effective Assessment of Peripheral Vascular Function Paul P. Breen, IEEE Member and Gaetano D. Gargiulo, IEEE Member 978-1-4244-7929-0/14/$26.00 ©2014 IEEE 4795