International Journal of Scientific & Engineering Research, Volume 4, Issue 9, September-2013 1969

ISSN 2229-5518

Wireless Sensors for Healthcare

Irfan Shaqiri

Abstract - Recent years the appearance of wireless biomedical sensor networks (W BSNs) in healthcare is very evident. They will cohabit with the in- stalled infrastructure, augmenting data collec-tion and real-time response. Samples of areas in which future medical systems can benefit the most from wireless sensor net-works are in-home assistance, smart nursing homes, and clinical trial and research augmentation. Wearable sensors will allow vast amounts of data to be collected and mined for next-generation clinical trials. Data will be collected and reported automatically, reducing the cost and inconvenience of regular visits to the physician. Also, biosensors are key part of wearable sensors playing important roles in detecting a lot of diseases, which cause death of millions people all over the world. Their key characteristics are given below and has been mentioned some type of biosensors.

Index Terms: W ireless Biomedical Sensor Networks (W BSNs), Healthcare, Wearable Sensors, Biosensors

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1 INTRODUCTION

n a wireless biomedical sensor network, a lot of little, bat- tery-powered computing devices are diffused throughout a physical environment. Each device is competent of moni- toring—sensing—and/or displaying—actuating—
Information. Sensing may include the collection of values for temperature, humidity, vibration, electrocardiogram, blood pressure, pulse, or other health-relevant data. An actuating device may cause an LED to blink, turn on lights, change col- ors on a display, display textual information, or any trigger other action that prompts a response or informs a human. WSNs are used in commercial, in-dustrial, environmental, and healthcare applications to monitor data that would be difficult or expensive to capture using wired sensors. A diversity of applications have been presented in the literature for wireless sensor networks.When applied to biomedical type applica- tions they are often referred to as wireless biomedical sensor networks (WBSNs) [1], which have a number of characteristics that differentiate them from standard WSNs and WLANs. A WBSN device is a packaged data collecting or actuating com- ponent, which includes a sensor and/or an actuator, a radio stack, an enclosure, an embedded processor, and a power de- livery mechanism. Depending on the device, it may also in- clude an antenna. Devices are held within an enclosure.A transceiver module is a class of device that is not packaged within an en-closure. A transceiver module usually combines an embedded processor, radio stack, antenna, and sometimes sensor and actuators, usually not packaged in an enclosure. Motes and the SHIMMER baseboard are two examples of transceiver modules.A sensor or actuator module combines the sensing and I/O on a plug-in board for the transceiver module described above.
By combining a transceiver module, a sensor module, an en- closure, and a battery, one would get a WBSN device. A sen- sor is the small piece of technology that actually interacts with the environment and which sends an appropriate signal to the embedded processor (micro-controller unit). Thus, for exam- ple, ECG sensor will note the rhythms of the heart, and send a
signal to the embedded processor. Depending on the design and the choice of technologies, the sensor may be within the same transceiver module as the processor, or it may be a plug- in addition to the transceiver module. The microcontroller unit (MCU) may decide to forward the sensed signal to an aggre- gator, or to do some processing, sleep for a while, or wait until the next cycle to forward the information from the sensor. When ready, the MCU sends the signal to the radio stack; the radio stack then uses a communications protocol (e.g., IEEE
802.15.4), and a transport protocol (e.g., ZigBee) with a data protocol (Continua or IEEE 11073) to pass the information to an aggregator (PC or cellular phone). The aggregator must, of course, have a compatible radio stack. The data is sent out of the radio stack to an antenna and thereby received by another antenna. The communication protocol layers transmit on a given frequency and format; for example, a 2.4-GHz FM transmission, using a 1-MHz-wide spread spectrum in the case of IEE 802.15.4.
Progression in telecommunication technology has made pos- sible data transmission over the wireless system. This has ena- bled remote patient monitoring which collects disease-specific metrics from biomedical devices used by patients in their homes or other settings outside of a clinical facility. Remote monitoring systems typically collect patient readings and then transmit it to a remote server for storage and later examination by the healthcare professionals. Once available on the server, the readings can be used in numerous ways by home health agencies, clinicians, physicians, and other authorized informal healthcare care providers [2].

2 WIRELESS BIOMEDICAL SENSOR NETWORKS

Wireless Biomedical Sensor Networks (WBSN) is a group of wireless network comprising low powered bio-sensor devices known as "motes" or "nodes” i.e., the convergence of bio- sensors using network technology in wireless ambience. In principle, it is an integration of embedded microprocessors, a radio device with limited amount of data storage [3]. Recent development of high performance microprocessor and novel sensing materials has stimulated great interest in the devel-

International Journal of Scientific & Engineering Research, Volume 4, Issue 9, September-2013 1970

ISSN 2229-5518

opment of smart sensors -physical, chemical or biological sen- sors combined with integrated circuits [4]. Although the field of biomedical sensors is relatively new, there has been numer- ous significant works previously where traditional sensor technologies have been applied in making biomedical meas- urements. This has helped to define the limitations as well as to set new direction for further research.

Fig. 1. Architecture of WBSNs Source [2]
WBSN, unlike wired monitoring system, can be used for long- term and continuous monitoring even when people move. The architecture of WBSN is shown above in Figure 1. The wireless mote can be integrated with various biosensors, i.e. ECG sen- sor, temperature sensor and etc. The physiological signals measured by the sensors are gathered by multi-hop mote wirelessly. The data acquired will be sent to server of a clinical facility via internet. The server stored the patient data into patient data base system. It is also capable of processing and analyzing the patient’s data. Any abnormality detected in the patient’s data at the server will produce an alert which will be sent to the healthcare professional i.e. using the short message service (SMS) system. Healthcare professionals can have ac- cess to the patient data on the server through internet using personal computer or personal digital assistant (PDA). More importantly, healthcare professional can be anywhere to ac- cess the patient data after receiving alert from the server.

3 BIOSENSORS FOR HEALTHCARE

Biological and biochemical processes have a very important role on medicine, biology and biotechnology. In recent years, thanks to improved techniques and devices, the usage of these products has increased.
A biosensor is a device composed of two elements:
1. A bioreceptor that is an immobilized sensitive biological
element (e.g. enzyme, DNA probe, antibody) recognizing the
analyte (e.g. enzyme substrate, complementary DNA, anti-
gen). Although antibodies and oligonucleotides are widely
employed, enzymes are by far the most commonly used bio-
sensing elements in biosensors.
2. A transducer is used to convert (bio) chemical signal result-
ing from the interaction of the analyte with the bioreceptor
into an electronic one. The intensity of generated signal is di-
rectly or inversely proportional to the analyte concentration.
Electrochemical transducers are often used to develop biosen- sors. These systems offer some advantages such as low cost, simple design or small dimensions.
Biosensors are categorized according to the basic principles of
signal transduction and biorecognition elements. According to
the transducing elements, biosensors can be classified as elec- trochemical, optical, piezoelectric, and thermal sensors [5]. Electrochemical biosensors are also classified as potentiom- etric, amperometric and conductometric sensors. The applica- tion of biosensor areas [6] are clinic, diagnostic, medical appli- cations, process control, bioreactors, quality control, agricul- ture and veterinary medicine, bacterial and viral diagnostic etc. A few advantages of biosensors are listed below:
• They can measure nonpolar molecules that do not re- spond to most measurement devices
• Biosensors are specific due to the immobilized system used in them.
• Rapid and continuous control is possible with biosen- sors
• Response time is short (typically less than a minute)
and practical
There are also some disadvantages of biosensors:
• Heat sterilization is not possible because of denatural- ization of biological material,
• Stability of biological material (such as enzyme, cell, antibody, tissue, etc.), depends on the natural proper- ties of the molecule that can be denaturalized under environmental conditions (pH, temperature or ions)
• The cells in the biosensor can become intoxicated by other molecules that are capable of diffusing through the membrane.

3.1 Biosensors for glucose measuring

Glucose can be monitored by invasive and non-invasive tech- nologies. Glucose sensors are now widely available as small, minimally invasive devices that measure interstitial glucose levels in subcutaneous fat. Requirements of a sensor for in vivo glucose monitoring include miniaturization of the device, long-term stability, elimination of oxygen dependency, con- venience to the user and biocompatibility. Long-term biocom- patibility has been the main requirement and has limited the use of in vivo glucose sensors, both subcutaneously and intra- vascular, to short periods of time. Diffusion of low-molecular- weight substances from the sample across the polyurethane

International Journal of Scientific & Engineering Research, Volume 4, Issue 9, September-2013 1971

ISSN 2229-5518

sensor outer membrane results in loss of sensor sensitivity. In order to address the problem, micro dialysis or ultra filtration technology has been coupled with glucose biosensors.
The current invasive glucose monitors commercially available
use glucose oxidase-based electrochemical methods and the
electrochemical sensors are inserted into the interstitial fluid
space. Most sensors are reasonably accurate although sensor error including drift, calibration error, and delay of the inter- stitial sensor value behind the blood value are still present [7]. The glucose biosensor is the most widely used example of an electrochemical biosensor which is based on a screenprinted amperometric disposable electrode. This type of biosensor has been used widely throughout the world for glucose testing in the home bringing diagnosis to on site analysis.

3.2 Biosensors for cardiovascular diseases

Cardiovascular diseases are highly preventable, yet they are major cause of death of humans over the world. One of the most important reasons of the increasing incidences of cardio- vascular diseases and cardiac arrest is hypercholesterolemia, i.e. increased concentration of cholesterol in blood [8]. Hence estimation of cholesterol level in blood is important in clinical applications. The early evaluation of patients with symptoms that indicates an acute coronary syndrome is of great clinical relevance. Biosensors for cholesterol measurement comprise the majority of the published articles in the field of cardiovas- cular diseases. In the fabrication of cholesterol biosensor for the estimation of free cholesterol and total cholesterol, mainly cholesterol oxidase (ChOx) and cholesterol esterase (ChEt) have been employed as the sensing elements [9]. Based on number and reliability of optical methods, a variety of optical transducers have been employed for cholesterol sensing, namely monitoring: luminescence change in color of dye, fluo- rescence and others .Other cardiovascular disease biomarkers are also quantified. CRP measurement rely mainly on immune sensing technologies with optical, electrochemical and acous- tic transducers besides approaches to simultaneous analytes measurement incorporated streptavidin polystyrene micro- spheres to the electrode surface of SPEs in order to increase the analytical response of the cardiac troponin used an assay based on virus nanoparticles for troponin I highly sensitive and selective diagnostic, a protein marker for a higher risk of acute myocardial infarction.
Early and accurate diagnosis of cardiovascular disease is cru- cial to save many lives, especially for the patients suffering the
heart attack. Accurate and fast quantification of cardiac mus- cle specific biomarkers in the blood enables accurate diagnosis and prognosis and timely treatment of the patients. It is ap- parent that increasing incidences of cardiovascular diseases and cardiac arrest in contemporary society denote the necessi- ty of the availability of cholesterol and other biomarkers bio- sensors.
The efforts directed toward the development of cardiovascular
disease biosensors have resulted in the commercialization of a
few cholesterol biosensors. A better comprehension of the bio-
reagents immobilization and technological advances in the
microelectronics is likely to speed up commercialization of the much needed biosensors for cardiovascular diseases.

3.3 Biosensors for cancer detection

Cancer is the leading cause of death in economically devel- oped countries and the second leading cause of death in de- veloping countries. This disease continues to increase globally largely because of the aging and growth of the world popula- tion alongside an increasing adoption of cancer-causing be- haviors, particularly smoking. Breast cancer is the most fre- quently diagnosed cancer and the leading cause of cancer death among females and lung cancer is the leading cancer site in males. Breast cancer is now also the leading cause of cancer death among females in economically developing coun- tries, a shift from the previous decade during which the most common cause of cancer death was cervical cancer [10]. Existing methods of screening for cancer are heavily based on cell morphology using staining and microscopy which are invasive techniques. Furthermore, tissue removal can miss cancer cells at the early onset of the disease. Biosensor-based detection becomes practical and advantageous for cancer clini- cal testing, since it is faster, more user-friendly, less expensive and less technically demanding than microarray or proteomic analyses.
However, significant technical development is still needed,
particularly for protein based biosensors. For cancer diagnosis
multi-array sensors would be beneficial for multi-marker
analysis. A range of molecular recognition molecules have been used for biomarker detection, being antibodies the most widely used. More recently, synthetic (artificial) molecular recognition elements such as nanomaterials, aptamers, phage display peptides, binding proteins and synthetic peptides as well as metal oxides materials have been fabricated as affinity

International Journal of Scientific & Engineering Research, Volume 4, Issue 9, September-2013 1972

ISSN 2229-5518

materials and used for analyte detection and analysis [11]. Antibodies (monoclonal and polyclonal) have been applied in cancer diagnostics tests targeting cancer cells and biomarkers. Polyclonal antibodies can be raised against any biomarker or cells and with the introduction of high throughput techniques, applying these molecules in sensors has been successful.

Table1 Cancer Biomarker Source [5]

4 CONCLUSIONS

In this paper we have discussed the characteristics of wireless biomedical sensor networks in medicine. We have shown that wireless biomedical sensor networks can be widely used in healthcare applications and this research area is in a high ac- tivity phase and in future it will be more implemented at hos- pitals with the only goal to help people to have medical ser- vices quickly.
We presented architecture of WBSNs where we described de-
tailed structure of the network. Also is given description of
some practical biosensors. Their principle and implementation
were described, mentioning key types of them which are using
nowadays with primary intent to save a lot of lives all over the world.

the 3rd Annual International IEEEEMBS Special Topic Conference on

Microtechnologies in Medicine and Biology Kahuku, Oahu, Hawaii u

12 - 15 May 2005.

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