Wearable biosensors (WBS) will permit continuous cardiovascular (CV) monitoring in a number of novel settings. Benefits may be realized in the diagnosis and treatment of a number of major diseases. WBS, in conjunction with appropriate alarm algorithms, can increase surveillance capabilities for CV catastrophe for high-risk subjects. WBS could also play a role in the treatment of chronic diseases, by providing information that enables precise titration of therapy or detecting lapses in patient compliance.
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| Wearable Bio-sensors (WBS) |
WBS could play an important role in the wireless surveillance of people during hazardous operations (military,fire-fighting, etc.), or such sensors could be dispensed during a mass civilian casualty occurrence. Given that CV physiologic parameters make up the “vital signs” that are the most important information in emergency medical situations, WBS might enable a wireless monitoring system for large numbers of at-risk subjects. This same approach may also have utility in monitoring the waiting room of today’s overcrowded emergency departments. For hospital inpatients who require CV monitoring, current biosensor technology typically tethers patients in a tangle of cables, whereas wearable CV sensors could increase inpatient comfort and may even reduce the risk of tripping and falling, a perennial problem for hospital patients who are ill, medicated, and in an unfamiliar setting.
INTRODUCTION:
INTRODUCTION:
The ring sensor is an ambulatory, telemetric, continuous health-monitoring device. This WBS combines miniaturized data acquisition features with advanced photoplethysmographic (PPG) techniques to acquire data related to the patient’s cardiovascular state using a method that is far superior to existing fingertip PPG sensors. In particular, the ring sensor is capable of reliably monitoring a patient’s heart rate, oxygen saturation, and heart rate variability. Technical issues, including motion artifact, interference with blood circulation, and battery power issues, will be addressed, and effective engineering solutions to alleviate these problems will be presented. Second, based on the ring sensor technology the clinical potentials of WBS monitoring will be addressed.
PRINCIPLE:
This wearable bio-sensor works on the basis of photo-plethysmographic principle. Plethysmographic determination in which the intensity of light reflected from the skin surface and the red cells below is measured to determine the blood volume of respective area.There are two types, transmission and reflectance.
COMPONENTS:
The Wearable Biosensor mainly composed of the following components:
- Optical Sensor Unit
- Analog and digital processing unit
- RF transmitter, all of which are encapsulated in a compact body
- Powered by a tiny cell battery used for wristwatches.
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| Overcoming artifact due to external force by placing the LED & PD more interior within the frame. |
The above figure shows the first ring sensor prototype that contains an optical sensor unit, analog and digital processing units, and an RF transmitter, all of which are encapsulated in a compact body and powered by a tiny cell battery used for wristwatches. The ring has a PIC microcomputer performing all the device controls and low-level signal processing, including LED modulation, data acquisition, filtering, and bi-directional RF communication. The acquiredwaveforms, sampled at 100 Hz, are transmitted to a PDA or a cellular phone carried by the patient through an RF link of 105 kbps at a carrier frequency of 15 MHz. The cellular phone then accesses aWeb site for data storage and clinical diagnosis.
An obvious source of signal corruption results from the direct interaction of the sensor unit with the wearer’s surrounding environment; e.g., holding objects, touching surfaces, etc. Thus, the body of the ring must separate the sensor unit in order to decouple the sensor unit from these interactions. To this end, a double ring configuration was designed and implemented, as shown in following. The disturbance force is born by the outer ring and is not transmitted to the inner ring holding the sensor unit. Moreover the outer ring serves as an optical shield for protecting the sensor unit from the ambient light. In this early development, the power consumption of the LEDs and the embedded CPU clock were a major bottleneck limiting the design. The distance between the LEDs and PDs had to be shortened for power saving considerations, and the CPU clock was minimized in order to extend the battery life to a few weeks. To evaluate the overall performance of motion artifact resistance, data were continually taken from a wearer performing daily office work (e.g., typing and writing) and the acquired data were examined to see how often the waveforms were corrupted and how many of them were usable. The result was that 35% of the data in a two-hour session was not corrupted and usable.
In order to know more about results obtained(output of WBS), various artifacts produced in WBS which prevents precise output (such as motion artifact) and how it can be eliminated through adopting methodologies like sensor arrangement, transmural pressure, using adaptive filter which involves LMS algorithm, noise rejection method please mail me( muthuvignesh88@gmail.com ). In addition to that, scattering of light is a typical problem in this WBS which must be considered as a severe problem.
