Introduction: Edema of the lower leg is often caused by serious medical condition, such as heart failure or kidney disease. Changes in the severity of edema often go unnoticed by the patient; therefore, prompt detection and notification to healthcare providers are important. We have developed a Bioimpedance sensor to continuously monitor the lower leg edema and transmit measurements to a nearby receiver and data logger. This is an ideal application for Medical Internet of things (IoMT), whereby notification is sent to the physician or another appropriate person. (We cannot yet actually implement IoMT because of FDA approval requirements.) The Sensor is attached directly to the lower leg using a strap or with an adhesive approved for medical use. No electrodes are applied directly to the skin; coupling is inductive/capacitive. Measurements are taken once every minute to prolong battery life. An LED-based pulse monitor will soon be implemented to provide more useful information for the doctor.
Materials and
Methods: Materials Our Bio-Impedance Sensor prototype consists of an oscillator module that drives a capacitive/inductive transmitter, The signal is coupled to the receiver via the skin. No direct DC contact with skin is needed. The receiver signal is then fed into a rectifier to convert the RF output to DC analog voltage output. Data acquisition and internet connectivity will be added. The prototype is in an enclosure with a medical grade adhesive for attachment to the leg.
Method The prototype sensor is attached to the lower leg as shown in the photo. Measurements are taken on the left leg and the right leg at different times of the day.
Results, Conclusions, and Discussions: Results We have shown the feasibility of using a Bioimpedance sensor to measure and continuously monitor the lower leg edema. The increasing importance of Internet of Things has been addressed and will be implemented to the point allowed without FDA approval. An important observation is that sensor output is dependent upon the exact location on the lower leg, although relative changes may be monitored over time if the sensor is kept in the same location. Typical measurements (analog signal output) with sensor placed in the same location: Person A: Left leg 5PM 0.65V Right leg 5PM 0.47V Right leg 1PM following day 0.52V Person B: 82 year old person with no visible edema and sensor, placed in the same location 0.34V
Conclusions: This prototype bioimpedance lower leg edema sensor has performed mostly as we predicted: * Measurements have been consistent with visible severity of edema, * The medical grade adhesive appears to be working well, eliminating the need for straps to hold the sensor in place. * The prototype has proven to be physically robust, as it has been accidently dropped several times with no damage. * Additional effort should be made to measure absolute edema level, rather than relative edema, over time. * A smaller and lighter sensor - easier to mount and less obtrusive - will be built.
Discussion Continuing and future research: * Testing on more subjects; wearing the sensor continuously for several days; and worn continuously for several days,; and testing on more people with no visible edema. * Implement data acquisition hardware/software and link to WiFi. * Attempting to measure an absolute level of edema, rather than relative values; possibly in units of grams of water content per gram of body tissue. * Preparation for use with Internet of Medical Things (IoMT). * Contact large companies with resources to obtain FDA approval, pursue IoMT, and take it to the next stage of development. We being a small enterprise need assistance to take this project to the next level.
.jpg "Fred Dyer, Bachelor photo")