BIO SENSORS
1. INTRODUCTION
Wearable sensors and systems have evolved to the point that they can be considered ready for clinical application. The use of wearable monitoring devices that allow continuous or intermittent monitoring of physiological signals is critical for the advancement of both the diagnosis as well as treatment of diseases.
Wearable systems are totally non-obtrusive devices that allow physicians to overcome the limitations of ambulatory technology and provide a response to the need for monitoring individuals over weeks or months. They typically rely on wireless miniature sensors enclosed in patches or bandages or in items that can be worn, such as ring or shirt. The data sets recorded using these systems are then processed to detect events predictive of possible worsening of the patient’s clinical situations or they are explored to access the impact of clinical interventions.
2.DEVELOPMENT OF WEARABLE BIOSENSOR
2.1.RING SENSOR
It is a pulse oximetry sensor that allows one to continuously monitor heart rate and oxygen saturation in a totally unobtrusive way. The device is shaped like a ring and thus it can be worn for long periods of time without any discomfort to the subject. The ring sensor is equipped with a low power transceiver that accomplishes bi-directional communication with a base station, and to upload date at any point in time.[1]
2.1.1 BASIC PRINCIPLE OF RING SENSOR
Each time the heart muscle contracts,blood is ejected from the ventricles and a pulse of pressure is transmitted through the circulatory system.
This pressure pulse when traveling through the vessels,causes vessel wall displacement which is measurable at various points.inorder to detect pulsatile blood volume changes by photoelectric method,photo conductors are used.normally photo resistors are used, for amplification purpose photo transistors are used.
Light is emitted by LED and transmitted through the artery and the resistance of photo resistor is determined by the amount of light reaching it.with each contraction of heart,blood is forced to the extremities and the amount of blood in the finger increases.it alters the optical density with the result that the light transmission through the finger reduces and the resistance of the photo resistor increases accordingly.The photoresistor is connected as a part of voltage divider circuit and produces a voltage that varies with the amount of blood in the finger.This voltage that closely follows the pressure pulse
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2.1.2WORKING
The LEDs and PD are placed on the flanks of the finger either reflective or transmittal type can be used. For avoiding motion disturbances quite stable transmittal method is used. Transmittal type has a powerful LED for transmitting light across the finger. This power consumption problem can be solved with a light modulation technique using high-speed devices. Instead of lighting the skiing continuously, the LED is turned ON only for a short time, say 10-100 ns, and the signal is sampled within this period, high frequency, low duty rate modulation is used for preventing skin-burning problem.
The motion of the finger can be measure with an optical sensor. This motion detector can be used not only for monitoring the presence of motion but also for cencelling the noise. By using PD-B as a noise reference, a noise cencellation filter can be built to eliminate the noise of PD-A that completes with the noise references used. And adaptive noise cancellation method is used.
The noise-canceling filter combines two sensor signals; one is the main signal captured by PD-A and the other is the noise reference obtained by PD-B. The main signal mostly consists of the truce pulsate signal, but it does contain some noise. If we know the proportion of noise contained in the main signal, we can sensate the contained in the main signal, we can generate the noise of the same magnitude by attending the noise reference signal and then subtract the noise from the main signal to recover the true pulsatile signal.
The ring has a microcomputer performing all the device controls and low level signal processing including LED modulation, data acquisition, filtering, and bi-directional RF communication. The acquired waveforms sampled at 100Hz are transmitted to a cellular phone carried by the patient through an RF link of 105Kbps at a carrier frequency of 915 MHz. The cellular phone accesses a website for data storage and clinical diagnosis.
2.1.3. Block diagram of ring sensor
Power Source
Power for light source, photo detector, RF transmitter and analog and digital processing units provided by a tiny cell battery used for wrist watches. Lifetime is 2 or 3 weeks.
Light Source
Light source for the ring sensor is the LED, approximately wavelength of 660 nm.
Photo Detector
Photo detector is normally photodiode or phototransistor used for detecting the signal from the LED.
RF Transmitter
It is used for transmitting the measured signals. Its carrier frequency is 915MHz.
LED Modulation
Power consumption problem can be solved with a lighting modulation technique. Instead of lighting the skin continually the LEDis turned on only for a short time, say 100-1000ns and the signal is sampled within the period. High frequency low duty cycle modulation implemented minimizes LED power consumption.[4]
Data Acquisition
It is used to collect the data from sensor and data are sampled and recorded.
Filtering
The signal from the PD-B as a noise reference a noise cancellation filter can be built to eliminate the noise of PD-A that correlates with the noise reference signal. For noise cancellation we use the adaptive noise filter.
2.1.4APPLICATIONS OF THE RING SENSOR
CATRASTOPHE DETECTION
Wireless supervision of people during hazardous operation. Eg:military,fire fighting
In an overcrowded emergency department CHRONIC MEDICAL CONDITION in cardiovascular desease for monitoring the hyper tension,chronic surveillance of abnormal heart failure
CATRASTOPHE DETECTION
Wireless supervision of people during hazardous operation. Eg:military,fire fighting
In an overcrowded emergency department CHRONIC MEDICAL CONDITION in cardiovascular desease for monitoring the hyper tension,chronic surveillance of abnormal heart failure
2.1.5 ADVANTAGES
· continous monitoring
· detection of transient phenomena
· promote further diagnostic and therapeutic measures
· easy to use
· reducing hospitalization fee
DISADVANTAGES
· initial cost is high
· limited number of physiological parameters are to be monitored
2.2.SMART SHIRT (WEARABLE MOTHERBOARD)
Smart shirt developed at Georgia
Research on the design and development of a smart shirt fort a combat casualty care has led to the realization of the world’s first wearable motherboard or an “intelligent” garment for the 21st century. The Georgia
2.2.1.REQUIREMENTS OF SMART SHIRT
Casualties are associated with combat and sometimes are inevitable. Since medical resources are limited in a combat scenario, there is critical need to make optimum use of the available resources to minimize the loss of human life, which has value that is priceless. In a significant departure from the past, the loss of even a single soldier in a war can alter the nations engagement strategy making it all the important to save lives.[2]
Similarly on the civilian side, the population is aging and the cost of the health care delivery is expected to increase at a rate faster than it is today. With the decreasing number of doctors in rural areas, the doctor/patient ratio is in certain instances reaching unacceptable levels for ensuring a basic sense of security when they leave the hospital because they feel “cutoff” from the continuous watch and care they received in the hospital. This degree of uncertainty can greatly influence their postoperative recovery. Therefore there is a need to continuously monitor such patients and give them the added peace of mind so that the positive psychological impact will speedup the recovery process.
Mentally ill patients need to be monitored on a regular basis to gain a better understanding of the relationship between their vital signs and their behavioral patterns so that their treatments can be suitably modified. Such medical monitoring of individuals is critical for the successful practice of telemedicine that is becoming economically viable in the context of advancements in computing and telecommunication, likewise continuous monitoring of astronauts in space, of athletes during practice sessions and in competition, of law enforcement personnel and combat soldiers in the line of duty are all extremely important.
2.2.2ARCHITECTURE
The GTWM was woven into a single –piece garment (an undershirt) on a weaving machine to fit a 38-40” chest. The plastic optical fiber (POF) is spirally integrated into the structure during the fabric production process without any discontinuities at the armhole or the segms using a novel modification in the weaving process.
An interconnection technology was developed to transmit information from (and to) sensors mounted at any location on the body thus creating a flexible “bus” structure. T-connectors –similar to “button clips” used in clothing are attached to the fibers that serve as a data bus to carry the information from the sensors (eg: ECG sensors) on the body.
The sensors will plug into these connectors and at the other end similar T-connector will be used to transmit their information for monitoring equipment or DARPS (Defense Advanced Research Projects Agency) personnel status monitor .By making the sensors detachable from the garments, the versatility I\of the Georgia Tech Smart Shirt has been significantly enhanced. Since shapes and sizes of humans will be different, sensors can be positioned on the right locations for all users and without any constraints being imposed by the smart shirt can be truly “customized”. Moreover the smart shirt can be laundered without any damage to the sensors themselves.
The interconnection technology has been used to integrate sensors for monitoring the following vital signs: temperature, heart rate and respiration rate .In addition a microphone has been attached to transmit the weavers voice data to monitoring locations. Other sensors can be easily integrated into the structure. The flexible data bus integrated into the stricture transmits the information from the suite of the sensors to the multifunction processor known as the Smart shirt controller. This controller in turn processes the signals and transmit them wirelessly to desired locations (eg: doctor’s office, hospital, battlefield). The bus also serves to transmit information to the sensors (and hence the weaver) from the external sources, thus making the smart shirt a valuable information infrastructure.
A combat soldier sensor to his body, pulls the smart shirt on, and attaches the sensors to the smart shirt. The smart shirt functions like a mo0therboard, with plastic optical fibers and other special fibers woven throughout the actual fabric of the shirt. To pinpoint the exact location of a bullet penetration, a “signal” is sent from one end of the plastic optical fiber to a receiver at the other end. The emitter and the receiver are connected to a Personal Status Monitor (psm) worn at the hip level by the soldier. If the light from the emitter does not reach the receiver inside the PSM, it signifies that the smart shirt has been penetrated (i.e.; the soldier has been shot). The signal bounces back to the PSM forum the point of penetration, helping the medical personnel pinpoint the exact location the solider wounds.[6]
The soldiers vital signs –heart rate, temperature, respiration rate etc. are monitored in two ways: through the sensors integrated into the T-shirt: and through the sensors on the soldier’s body, both of which are connected to the PSM. Information on the soldiers wound and the condition is immediately transmitted electronically from the PSM to a medical triage unit somewhere near the battlefield. The triage unit them dispatches the approximate medical personnel to the scene .The Georgia tech smart shirt can help a physician determine the extent of a soldiers injuries based on the strength of his heart beat and respiratory rate. This information is vital for accessing who needs assistance first during the so-called “Golden Hour” in which there are numerous casualties.
2.2.3. APPLICATIONS OF SMART SHIRT
· Combat casualty care.
· Medical monitoring.
· Sports/ Performance monitoring.
· Space experiments.
· Mission critical/ hazardous application.
· Fire- fighting.
· Wearable mobile information infrastructure.
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The vital signs information gathered by the various sensors on the body travels through the smart shirt controller for processing, from these, the computed vital signals are wirelessly transmitted using the “communication information infrastructure” in place in that application (e.g.: the firefighters, communication systems, battlefield communication infrastructure, the hospital network) to the monitoring station. There, the back-end Data display and Management system – with a built –in knowledge –based decision support system- in reverse these vital signs ask in real-time and provide the right response to the situation.
2.2.4.IMPACT OF THE SMART SHIRT
The smart shirt will have significant impact on the practice of medium since it fulfills the critical need for a technology that can enhance the quality of life while reducing the health care cost across the continuum of life that is from newborns to senior citizens, and across the continuum of medical care that is from hospitals and everywhere in between.
The smart shirt can contribute to reduction in health care cost while enhancing the quality of life. For instance, patients could wear the smart shirt at home and be monitored by a monitoring station; thereby avoiding hospital stay cost and reducing the overall cost of healthcare. At also same home, a home setting can contribute to faster recovery. For example, if the patient recovering at home from heart surgery is wearing the smart shirt, the ECG can be transmitted wirelessly (through mobile phone, internet etc) to the hospital on a regular basis. This monitoring will help the patient feel more “secure” and will facilitate the recuperation while simultaneously reducing the cost time associated with recovery. Moreover, in the event of an emergency, the doctor can be notified instantaneously. Using the online medical records (available over the web) the physician can administrate the right investment at the right time at the right cost and indeed save a life, thereby realizing the full potential of the smart shirt technology.
Further more, persons who have known disorders can wear the smart shirt and be under constant monitoring of the physical conditions by medical personnel. Yet another potential impact of the smart shirt technology is the eventual disappearance of geographical/physical boundaries as barriers for individual seeking the best in healthcare worldwide.
The smart shirt technology has the means to provide unobstructed monitoring for individuals and can thereby play a critical role disease management for the large numbers of individuals at risk for high blood pressure, heart disease, diabetes, chronic bronchitis, and depression by enabling early systematic intervention.
2.2.5.Advantages of the Smart Shirt
· Continuous monitoring
· Right Treatment at the right time at the right cost
· Easy to wear and takeoff.
· Reducing the health care cost
Disadvantages of the Smart Shirt
· Initial cost is high
· Battery life is less
3.FUTURE TRENDS
By providing the “platform” for a suite of sensors that can be utilized to monitor an individual unobtrusively. Smart Shirt technology opens up existing opportunities to develop “adaptive and responsive” systems that can “think” and “act” based on the users condition, stimuli and environment. Thus, the rich vital signs delta steam from the smart shirt can be used to design and experiment “real-time” feedback mechanism (as part of the smart shirt system) to embrace the quality of care for this individual by providing appropriate and timely medical inspections.
Certain individuals are susceptible to anaphylaxis reaction (an allergic reaction) when stung by a bee or spider and need a shot of epinephrine (adrenaline) immediately to prevent above illness or even fatalities. By applying advancement in MEMS (Micro-Electromechanical Systems) technology, a feedback system including a dry delivery system-can be integrated into the smart shirt. Of course mechanism to guard against inadvertent administration of dry can be built as a part of the control system.
Likewise, the Smart shirt’s delta acquisition capabilities can be used to detect the condition when an individual is lapsing into a diabetic shock and this integrated feedback mechanism can provide the appropriate response to prevent a fatality. Thus, the smart shirt represents yet another significant milestone in the endeavor to save and enhance the quality of human life through the use of advanced technologies.
4. Conclusion
The ring sensor and smart shirt are an effective and comfortable, and mobile information infrastructure that can be made to the individual’s requirements to take advantage of the advancements in telemedicine and information processing. Just as special-purpose chips and processors can be plugged into a computer motherboard to obtain the required information processing capability, the smart shirt is an information infrastructure into which the wearer can “plug in” the desired sensors and devices, thereby creating a system for monitoring vital signs in an efficient and cost effective manner with the “universal“ interface of clothing.
Advanced technologies such as the smart shirt have at partial to dramatically alter its landscape of healthcare delivery and at practice of medicine as we know them today. By enhancing the quality of life, minimizing “medical” errors, and reducing healthcare costs, the patient-control wearable information infrastructure can play a vital role in realizing the future healthcare system. Just as the spreadsheet pioneered the field of information processing that brought “computing to the masses”. It is anticipated that the smart shirt will bring personalized and affordable healthcare monitoring to the population at large, thus leading to the realization of “Affordable Healthcare, Any place, Anytime, Anyone”.
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