There is an enormous clinical problem in optimally managing the fluid status for a number of disease states, including chronic kidney disease (CKD), congestive heart failure (CHF), liver failure, and lymphedema. Currently, serial physical examinations by a skilled clinician provide the input for clinical decision making. However, serial examinations are a challenge, especially in rural, medically underserved communities and quantitative, operator independent hydration status assessments are lacking. Remote monitoring telehealth initiatives using weights and blood pressure measurements provide some information, but technology allowing rapid, robust, repeatable measurements of hydration status would be a major advance. In recent years, bioimpedance measurements have been shown to be useful in monitoring dialysis patients, where a dry weight determination is needed for optimal fluid status management. However, confounding effects from cellular ionic content hamper future evolution of this technique. We have developed approaches for strain-based bioimpedance measurements that will allow this field to advance. In addition, we have laid the groundwork to develop an alternative and complementary method for quantifying peripheral edema. The use of ultrasound strain imaging dynamically and quantitatively characterizes changes of a subsurface elastic medium under stress. Using these strain measurements, along with bioimpedance readings, we can completely characterize the visco- and poro-elastic parameters of a patient's edematous state. However, this technique is untested and needs to be developed and validated. Edematous tissue can be viewed as a poroelastic material containing both fluid and solid components. While bioimpedance measurements are responsive to volume fluid changes in tissue, ultrasound measurements primarily depend on the solid component of tissue. Combined, these modalities promise to offer a more complete analysis of edematous tissue while quantifying fluid hydration status with a precision yet seen clinically. Parallel to these concerns over hydration status, remote care in the form of telehealth and telemedicine is emerging as an important tool for numerous patient groups. Especially for rural, underserved communities, the ability to remotely communicate important reliable indicators of hydration status to their physicians can dramatically improve our ability to address health concerns. The overall goal of this proposal is to develop a clinically useful, robust, reproducible, quantitative tissue hydration measurement apparatus that will be low-cost, suitable for home or remote patient monitoring, with secure data handling. We will accomplish this by first developing appropriate hardware and software to independently test the ability of ultrasound and bioimpedance to detect changes in poroelastic structures under quasi-static and dynamic loading conditions. Algorithms and models based on the collected data will be developed and validated using PIV, load cell, and pressure transducer measurements. Parallel to this, a telehealth program will be developed including both the wireless capabilities needed as well as preliminary testing on alerts and warning systems that could be utilized once fluid hydration status readings are incorporated into remote monitoring regimes. Finally, a compact, convenient device will be developed ready for clinical testing combining both ultrasound and bioimpedance modalities to accurately and quantitatively determine tissue hydration of peripheral extremities and transmit the data securely over telehealth communication lines. Management of patients with diuretics or extracorporeal therapies requires proper assessment of volume status. This is important for a wide variety of clinical situations. Importantly, this proposal supports the Veterans Administration telehealth initiative and will improve the health of Veterans needing remote health monitoring.
This proposal will develop and test a novel device that accurately measures excess fluids (edema) to guide therapy that will improve the health of people with kidney disease and heart disease. The proposal will also integrate advanced remote monitoring methods (telehealth) with this novel device to meet the clinical needs of patients in underserved regions in the United States.