Real Time Telemonitoring of Medical Vital Signs

Real Time Telemonitoring of Medical Vital Signs

HARITON COSTIN1,2, CRISTIAN ROTARIU1,2, IOANA ALEXA3, GINA CONSTANTINESCU3, V. CEHAN4, B. DIONISIE3, GLADIOLA ANDRUSEAC1, D.

AROTARITEI1, B. MUSTAłĂ5, OCTAVIA MORANCEA6, F. ADOCHIEI1, R. CIUBOTARIU1, E. CRAUCIUC3, MONICA SCUTARIU3

1 “Gr.T. Popa” University of Medicine and Pharmacy, Faculty of Medical Bioengineering, Iasi, ROMANIA; e-mail: [email protected]

2 The Institute for Computer Science, Romanian Academy – Iasi Branch, ROMANIA 3 “Gr.T. Popa” University of Medicine and Pharmacy, Faculty of Medicine, Iasi, ROMANIA 4 “Gh. Asachi” Technical University, Faculty of Electronics and Telecommunications, Iasi

5 Romsoft SRL, Iaşi, ROMANIA 6 CMed SRL Timişoara, ROMANIA

Abstract — This paper presents the most complex Romanian telemedical project, TELEMON, that has as goals researches, design and implementation of an electronic-informatics-telecom and scalable system, that allows the automatic and complex telemonitoring, everywhere and every time (at home, in hospitals, at work, of mobile subject, etc), in (almost) real time, of the vital signs of persons with chronic illnesses, of elderly people, of those having high medical risk and of those with neuro-locomotor disabilities. The main objective of this pilot project is to enable personalized medical teleservices delivery and patient safety enhancement based on an earlier diagnosis, and to act as basis for a public service for telemedical procedures.

Keywords — telemedicine, biomedical equipment, biomedical signal analysis, wireless personal area net-work, fall-detection.

1 Introduction Telemedicine is part of the expanding use of com-munications technology in health care being used in prevention, disease management, home health care, long-term care, emergency medicine, and other ap-plications. In Romania, the diversification of tele-communication networks and advances in commu-nications technologies, including the Internet, has considerable potential as a medium for telemedicine applications. So, we propose doctors a technical solution for telemonitoring patients or elderly peo-ple.

The proposed project enables to design a secure multimedia transmission (medical telemetry, digital images, video, and text) and a secure medical re-cords acquisition system in order to enhance the telemedical consultancy services. The main objec-tive of this project is to enable personalized teleser-vices delivery and patient safety enhancement based on an earlier diagnosis with medical telemetry using biosignals, images [1], text transmissions, and also applying the suitable treatment according to the remote medical experts’ recommendations [2][16].

Our project will allow persons having different (chronic) diseases and to elderly/lonely people to be monitored from medical point of view. In this way the medical risks and accidents will be diminished. The TELEMON system will act as a pilot project

destined to the implementation of a public e-health service, “everywhere and every time”, in real time, for people being in different hospitals, at home, at work, during the holidays, on the street etc.

The use of wireless ECG is suitable for continu-ous long-time cardiac activity monitoring as a part of a diagnostic procedure, can achieve medical as-sistance for a chronic condition, and ECG can be supervised during recovery from an acute event or surgical procedure. For instance, the computer-assisted rehabilitation involves unwieldy wires be-tween sensors and monitoring device that are not very comfortable for normal activity.

The long term monitoring of human respiration is important for a number of medical conditions in-cluding rhythm analysis, polysomnography, stress monitoring and ischemic heart disease or heart fail-ure.

The number of deaths from heart conditions caused by high blood pressure continues to increase. Early detection and treatment of high blood pressure is critical to prevent future heart problems, and a variety of home monitoring devices are available for this purpose.

2 Materials and Methods The main objective of this project is the achieve-ment of an integrated system, mainly composed by

Proceedings of the 2nd WSEAS International Conference on BIOMEDICAL ELECTRONICS and BIOMEDICAL INFORMATICS

ISSN: 1790-5125 127 ISBN: 978-960-474-110-6

the following components that are near patient (Fig-ure 1): a personal network of wireless transducers (RPT) on the ill person, a network of transduc-ers/actuators for domotics, a data multiplexing block and a personal computer (PC). After local signal or image processing, according to the specific moni-tored feature, the salient data are transmitted via one of internet, GSM/GPRS or a telephonic line to the database server of the Regional Telemonitoring Centre. The personal network of transducers (RPT) includes medical devices for vital signs (ECG, heart rate, arterial pressure, oxygen saturation, body tem-perature), a movement sensor, eventually a respira-tion one, all these components having radio micro-transmitters, which allows an autonomic movement of the subject. The project will also approach the situation of the mobile subject. The data processing will be done by a PDA (Personal Digital Assistant) having GPS localization, and data transmission will be obtained by using GSM / 3G module of the PDA. Concerning the application programs, they act and correlate on two levels: a local data processing, near the patient, as well as another one database server. So, the general software architecture will be a cli-ent-server one, and the project will develop a so-called SOA – Service Oriented Architecture - which is a standards-based approach to manage services made available by different software packages for reuse and reconfiguration. Services are written to common protocols that are interchangeable, unlike today’s programmatic interfaces that are unique to each software application and typically vary by hardware platform, software language, and operat-ing system. In healthcare the situation is the same: there are a lot of applications, running on different platforms. The SOA can be a solution to use all the achievements for building a consistent process that can save time and money [3].

The results of data processing are in principal and if necessary different locally generated alarms, transmitted to the central server, to the family or specialist doctor, to the ambulance or to a hospital. Other results of locally or on server data processing will be different medical statistics, necessary for the evaluation of health status of the subject, for the therapeutic plan and for the healthcare entities.

The TELEMON system includes the following hardware and software components:

(A) A local sub-system, composed by (Figure 1):

1. a personal network of wireless medical sensors / transducers (RPT) for vital signs (ECG, heart rate, arterial pressure, oxygen saturation, body tempera-ture), a movement transducer (accelerometer), a respiration one, all these having radio micro-transmitters [4],[5],[6];

2. a tri-axial accelerometer – alerts home care personnel at a remote site that a monitored people has fallen down and monitors continuously the per-son’s activity. The user’s activity monitoring allows the characterization of users' mobility for diagnosis purposes;

3. a network of sensors /transducers/ actuators for domotics and audio communication patient – care-giver [7],[8],[9];

4. a video camera; 5. a personal computer, interfaced by radio with

the above sub-systems; 6. for mobile subject the data processing will be

done by a PDA interfaced with the personal net-work, and data transmission will be yielded by GSM/GPRS/UMTS and GPS modules of the PDA;

7. a local network of „ad hoc” type, composed by minicomputing units with radio transmission of data and necessary to cover a specific surface [10], [11].

(B) A server computer for the main database and other applications programs, situated at the Re-gional Telemonitoring Centre (CTMR).

(C) A server computer for tele–diagnosis (on-line consultation) and tele–consulting (off-line), where a video–conference program will be installed.

(D) Software applications for: 1. medical data acquisition and processing, do-

motics signals analysis, patient images analysis [1],[12], data transmission to central server;

2. the same functions as above, but for mobile pa-tient;

3. interface programs for duplex communication between local sub-system and central server;

4. specific alarms generating and their transmis-sion to the Ambulance, family doctor, to the special-ist or to a nurse; here there are necessary decision aided /expert systems based on medical specific knowledge [13],[14];

5. specific applications of e-rehabilitation and e-learning;

6. extra data processing programs, at the central server level (medical statistics, researches, etc.)

(E) Programs for data/knowledge bases (includ-ing user-interfaces) installed on the server.

(F) A program for the informatics management of the system, installed on server.

3 Results The TELEMON system is built around a database server which receives data from local subsystems and also from mobile subsystems. The transferred information to database server are represented by those data above the limits, by medical recordings and also by audio/video recordings. The database server stores the recordings and is capable to send


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alarms to the ambulance service and patient’s doc-tor. Also, the database server can be connected to another database server, for example a hospital server, in order to send the patient’s medical data. The subsystems are connected to the database server through an Internet connection (if it is available), through GSM or a telephone line (dial up).

The Local Subsystem for the monitoring of the patient at home or in hospital (Figure 1) is built around a personal computer (PC) or a PDA which receives data from the patient.

The medical devices allowing monitoring of the vital parameters are the following [15], [16], [17], [21], [22]:

a) a 3-leads ECG module records and transmits data through a radio transceiver interface;

b) the oxygen saturation module (SpO2), that also computes the cardiac rhythm;

c) the arterial pressure module, with serial inter-face;

d) the body temperature module; e) the respiration module; f) the fall detection module.

The modules (a), (d), (e), (f) were made by our re-search team, while module (b) and (c) were chosen from the market and were integrated in Telemon system.

These modules transmit data to a PDA or a PC through radio transceivers (eZ430 boards), can op-erate in the 2.4 GHz band, and have 50m/125m range indoors/outdoors.

The Figure 9 represents the block diagram of the personal server (PDA) running a personal health monitor, that is responsible for a number of tasks and provides a transparent interface to the wireless medical sensors, an interface to the user, and an interface to the central server by using the GSM connection. In the case when the patient is in a bad condition and he needs an emergency medical assis-tance, the PDA can send an alarm to a database server, including the precise coordinates of the pa-tient by using the internal GPS module.

The outputs of the personal sensors network are connected to a radio module that sends the data to the PC. A very important feature of the network and also of the radio module is their low power con-sumption. Another component of a local subsystem is the sensors/actuators for domotics. The domotics sensors collect data from different points of the house sends them to the PC. The PC takes the deci-sions and sends commands to specific actuators.

The Local Subsystem also allows the video moni-toring of the patient through a video camera con-nected to the PC. The PC records and stores images of the patient during the acquisition of the medical

parameters, process these images and can send to the database server images and also processing re-sults (e.g., alarms).

The PC is equipped with a radio module that re-ceives data from the patient’s personal network, runs the monitoring algorithms, activates the alarms if the medical parameters are above the limits and sends the results to the database server. The PC is connected to the database server through an Internet, GSM or dial up connection.

Figure 2 shows our ECG module, Figure 6 – the thermometer unit and Figure 7 represents the GUI (Graphical User Interface) for the ECG acquisition and analysis. Our wireless personal area network is realized by using a custom developed sensors modules for physiologic parameters measurement and a low power microcontroller board (eZ430-RF2500 Board from Texas Instruments). The network is wirelessly connected to a personal server (PDA - Fujitsu Sie-mens LOOX T810) that receives the information from sensors.

The eZ430-RF2500 is a complete MSP430 [19] wireless development tool providing all the hard-ware and software for the MSP430F2274 microcon-troller and CC2500 2.4GHz wireless transceiver [20].

Operating on the 2.4 GHz unlicensed industrial, scientific and medical (ISM) bands, the CC2500 provides extensive hardware support for packet handling, data buffering, burst transmissions, au-thentication, clear channel assessment and link qual-ity. The radio transceiver is also interfaced to the MSP430 microcontroller using the serial peripheral interface.

The USB interface enables eZ430-RF2500 to re-motely send and receive data through USB connec-tion using the MSP430 Application UART.

Figure 1 shows a simplified block diagram of the personal area network platform and Figure 11 - the personal server made by using a PDA (Fujitsu Sie-mens Loox T830). Each sensor module is powered by batteries and has as the features an ultra low power Texas Instruments MSP430 microcontroller, a Chipcon CC2500 radio interface in the 2.4 GHz band.


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Figure 1. The local subsystem for home monitoring

of the patient

The 3-lead ECG amplifier (Figure 2) [3] is a cus-

tom made device. It has for each channel a gain of 500, is DC coupled and has a cut-off frequency of 35 Hz. The high common mode rejection (>90 dB), high input impedance (>10 MΩ), the fully floating patient inputs are other features of the ECG ampli-fier.

Figure 2. The ECG amplifier (block diagram)

In order to have a good signal to noise ratio, dif-

ferential amplifiers are used (Figure 3). Since the output is proportional to the difference between the two voltages, this circuit has a fairly good common mode rejection. Unfortunately, the differential am-plifier’s performance is limited due to low input impedance. This problem has been avoided by in-corporating a dual instrumentation amplifier in place of a differential amplifier.

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Figure 3. The ECG amplifier (schematic – 1 chan-

nel) The instrumentation amplifier used (INA2321), is

a microPower, single-supply CMOS dual device from Texas Instruments. The INA2321 provides low-cost, low-noise amplification of differential signals a micropower current consumption of just 40µA/channel and a high CMRR > 90 dB, and it is suitable to use in physiological amplifiers, in par-ticular for ECGs.

The impedance between pins 1, 12, and 13 (or 7, 9 and 10), determines the gain of the INA2321. With an internally set gain of 5 per amplifier, the INA2321 can be programmed for gains greater than 5 with gain error guaranteed to be less than 0.1%. Errors from external resistors will add directly to the guaranteed error, and may become dominant error sources. A gain of 5 was chosen for this stage of the circuit.

The INA2321 inputs are protected by ESD diodes that will conduct if the input voltages exceed the power supplies by more than 500mV. Momentary voltages greater than 500 mV beyond the power supply can be tolerated if the current through the input pins is limited to 10 mA. This is easily ac-complished with input resistors (100K).

The second stage is a low pass filter with a gain of 100 and it is used to eliminate the high frequency noise above 35 Hz.

The operational amplifier used in the right-leg common-mode feedback circuit is the OPA 2366, a dual amplifier. The circuit sends an inverted version of the common-mode interference to the patient’s right leg, with the aim of cancelling the interference and protecting the signals from the leads by shield-ing the signal cable.

The ECG amplifier is powered by two AAA 1.5V alkaline batteries through the Voltage Regulator. The regulator in built around TPS60204 circuit and the schematic in represented in the Figure 4.


ISSN: 1790-5125 130 ISBN: 978-960-474-110-6

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The TPS60204 is a step-up, regulated charge

pumps that generates a 3.3V±4% output voltage from a 1.8V to 3.6V input voltage. The device is typically powered by two Alkaline, NiCd, or NiMH battery cells and operates down to a minimum sup-ply voltage of 1.6V. Minimum continuous supply current is 100 mA from a 2V input. Only four exter-nal capacitors are needed to build a complete low-ripple dc/dc converter. The push-pull operating mode of two single-ended charge pumps assures the low output voltage ripple, as current is continuously transferred to the output.

The TPS60204 circuit is programmed by using the EN pin. Setting the EN pin to low disables the device, shuts down all internal circuits, and discon-nects the output from the input. Setting the EN pin to high enables the device and programs it to run.

Figure 5 shows the practical ECG experimental module made by our team and Figure 6 – the graphical user interface for 3-leads ECG acquisition.

Figure 5. The 3-leads ECG module made by us

Figure 6. The ECG acquisition and analysis of a

patient *

Figure 7 represents the thermometer module. For the body temperature measurement we use the TMP275 temperature sensor (Texas Instruments). The TMP275 is a 0.5°C accurate, two-wire, serial output temperature sensor available in an SO8 pack-age. The TMP275 is capable of reading tempera-tures with a resolution of 0.0625°C. The TMP275 is directly connected to the ez430-RF2500 using the I2C bus and requires no external components for operation except for pull-up resistors on SCL and SDA. The accuracy for the 35-45°C interval is be-low 0.2 °C and the conversion time for 12 data bits is 220ms typical.

The Personal server samples the signal from the temperature sensor once per second and computes the status of the patient for the following tempera-ture values: Low temperature – when temperature falls below 35°C; High temperature – when temperature rises above 38°C; Normal temperature – between the above values.

Figure 7. The thermometer module

* The respiration module uses one of the most

usual methods to sense breathing - to detect airflow using a nasal thermistor [22]. Although most appli-cations require only breathing detection, some ap-plications and diagnostic procedures require moni-toring of the respiratory rhythm.

Our wireless respiration sensor uses a thermistor for long-time monitoring during the normal activity. The sensor is designed using MSP430F2274 micro-controller with an on-chip 10 bit A/D converter for data acquisition and CC2500 2.4GHz wireless transceiver.

The thermistor detects changes of breath tempera-ture between ambient temperature (inhalation) and lung temperature (exhalation). A thermistor placed in front of a nose detects breathing as a temperature change.


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The used thermistor is a 0603 SMD type and has the following characteristics: Rnom = 10kΩ at 25°C, B = 3380, 1% tolerance.

Figure 8 presents breathing cycles recorded using the MSP430F2274 A/D converter with 10 Hz sam-pling frequency.

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Figure 8. The thermistor sensor and temperature module (schematic, time representation and board)

The Personal server on patient (Figure 10) is

made using a PDA and computes the following res-piration parameters:

Breathing amplitude - calculated for every breathing cycle as a difference between minimum (Inhalation) and maximum thermistor voltage (Ex-halation);

Breathing interval – measured between two minimums representing two inhalations;

Breathing frequency calculated from the breath-ing interval as a number of breaths per minute. Normal breathing frequency is 12-20 cycles/minute.

We consider two types of respiration: Normal respiration, when every breath lasts more

than 0.5 seconds. Apnoea, when the breathing is missing for more

than 10 seconds. Sleep apnoea can last more than 120 seconds.

* The pulsoximeter sensor used is Micro Power

Oximeter board from Smiths Medical [23] (Figure 9). The same sensor can be used for heart-rate detec-tion and SpO2. The probe is placed on a peripheral point of the body such as a finger tip, ear lobe or the nose. The probe includes two light emitting diodes (LEDs), one in the visible red spectrum (660 nm) and the other in the infrared spectrum (905 nm). The percentage of oxygen in the body is computed by measuring the intensity from each frequency of light after it transmits through the body and then calculat-ing the ratio between these two intensities.

The pulsoximeter communicates with the eZ430-RF2500 through asynchronous serial channel at

CMOS low level voltages. Data provided includes % SpO2, pulse rate, signal strength, plethysmogram and status bits and is sent to the eZ430-RF2500 at a baud rate of 4800 bps, 8 bits, one stop bit and no parity.

The Micro Power Oximeter has the following

measurement specifications: range 0-99% functional SpO2 (1% increments), accuracy ±2 at 70-99% SpO2 (less than 70% is undefined), pulse range 30-254 BPM (1 BPM increments), accuracy ±2 BPM or ±2% (whichever is greater).

Figure 9. The Micro Power Oximeter and RF unit

*

For the blood pressure measurement, a commer-cially available A&D UA-767PC BPM [24] was used. The blood pressure monitor (BPM) takes si-multaneous blood pressure and pulse rate measure-ments. It includes a bi-directional serial port connec-tion communication at 9600 kbps. An eZ430-RF2500 communicates with the BPM on this serial link to start the reading process and receives the patient’s blood pressure and heart rate readings. Once the readings are received, the eZ430-RF2500 communicates with the network and transmits them to the Personal Server.

The Personal server computes blood pressure and defines the status of the patient by using the follow-ing blood pressure values: Hypotension: systolic < 90 mmHg or diastolic < 60 mmHg; Normal: systolic 90–119mmHg and diastolic 60–79 mmHg; Pre-hypertension: systolic 120–139 mmHg or 80–89 mmHg; Stage 1 Hypertension: systolic 140–159mmHg or diastolic 90 – 99 mmHg; Stage 2 Hypertension: systolic ≥ 160mmHg or dia-stolic ≥ 100 mmHg;

* There are some statistics (e.g. in 2035 about 1/3

of Europeans will be more than 65 years old, 30% of the older persons fall at least once a year, 75% of fall’s victims are elderly, and fall is responsible of 70% of accidental death in persons aged 75+) which lead to a continuous concern for developing reliable, easy to use and robust fall detection systems.

Our module for fall detection of humans is based on accelerometer technique. By using two tri-axial accelerometers at separate body locations, our sys-tem can recognize four kinds of static postures:


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standing, bending, sitting, and laying. Motions be-tween these static postures are considered as dy-namic transitions. Linear acceleration and angular velocity are measured to determine whether motion transitions are intentional. If the transition before a lying posture is not intentional, a fall event is de-tected. Our method for the human fall Detection (HFD) uses: 1. the ADXL330 Accelerometer (Figure 10); 2. eZ430-RF2500 Wireless Modules; 3. a CVI coded GUI.

The ADXL330 is a small, thin, low power, com-plete three axis accelerometer with signal condi-tioned voltage outputs, all on a single monolithic IC. The product measures acceleration with a minimum full-scale range of ±3 g. It can measure the static acceleration of gravity in tilt-sensing applications, as well as dynamic acceleration resulting from mo-tion, shock, or vibration.

Figure 10. The functional block diagram of 3-axis

accelerometer module for fall detection

A microcontroler calculates the aA and aB accelerations using the formula:

. (1) Here, aA and aB are the chest and thigh vector

magnitude linear acceleration. We determine if the subject has fallen if the con-

dition:

| aAmax -aAmin | < 0,4g ^ | aBmax –aBmin | < 0,4g (2)

is valid. *

In the Figure 11 it is represented the block dia-gram of the personal server, that were implemented by means of a PDA (Fujitsu-Siemens Loox T830). This personal medical monitor is responsible for a number of tasks, providing a transparent interface to the wireless medical sensors, an interface to the patient, and an interface to the central server.

Figure 11. The Personal server (block diagram) The USB interface (Figure 12) is realized by us-

ing a serial to USB transceiver (FT232BL) from FTDI [25] and enables eZ430-RF2500 to remotely send and receive data through USB connection us-ing the MSP430 Application UART. All data bytes transmitted are handled by the FT232BL chip. It also contains a voltage regulator (TPS77301) to provide 3.3 V to the eZ430-RF2500.

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Figure 12. The Personal server interface (trans-

ceiver and voltage regulator) The software on the Personal Server receives

real-time patient data from the sensors and processes them to detect anomalies.

a) b)


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c) d)

Figure 13. The Personal server interface: (a) 3 ECG traces, (b) one ECG trace, pulse waveform and

SpO2, (c) 3 accelerometer traces, (d) systolic and diastolic pressure from BPM

The software working on the Personal Server

(Figure 13) was written by using C# from Visual Studio.NET, version 8. The software displays tem-poral waveforms, computes and displays the vital parameters and the status of each sensor (the battery voltage and distance from the Personal Server). The distance is represented in percent of 100 computed based on RSSI (received signal strength indication measured on the power present in a received radio signal).

If the patient has a medical record that has been previously entered, information from the medical record (limits above the alarm become active) is used in the alert detection algorithm.

The following physiological conditions cause alerts: - low SpO2, if SpO2 < 90%; - bradycardia, if HR < 40 bpm; - tachycardia, if HR > 150bpm; - HR change, if ∆HR / 5 min > 20%; - HR stability, if max HR variability from past 4 readings > 10% ; - BP change if systolic or diastolic change is > ±10% .

When an anomaly is detected in the patient vital signs, the Personal server software application gen-erates an alert in the user interface and transmits the information to the TELEMON Server.

4. Conclusion

In this paper it is presented a project that aims to develop a secure multimedia, scalable system, de-signed for medical consultation and telemonitoring services. The main goal is to build a complete pilot system that will connect several local telecenters into a regional telemedicine network. This network enables the implementation of teleconsultation,

telemonitoring, homecare, urgency medicine, etc. for a broader range of patients and medical profes-sionals, mainly for family doctors and those people living in rural or isolated regions [18].

The Regional Telecenter in Iasi, situated in the Faculty of Medical Bioengineering, will allow local connection of hospitals, diagnostic and treatment centers, as well as a local network of family doctors, patients, paramedics and even educational entities. As communications infrastructure, we aim to de-velop a combined fix-mobile-internet (broadband) links.

We’ve already implemented and tested telecon-sultation and telemonitoring of vital signs applica-tions.

The proposed system will also be used as a warn-ing tool for monitoring during normal activity or physical exercise.

Such a regional telecenter will be a support for the developing of a regional medical database, that should serve for a complex range of teleservices such as teleradiology, telepathology, teleconsulting, telediagnosis, and telemonitoring. It should also be a center for continuous training and e-learning tasks, both for medical personal and for patients.

Besides the medical and technical objectives, TELEMON project also proposes important eco-nomic objectives: • the decrease of budgetary and personal expenses

dealing with the unjustified transport of patients to the hospital;

• „zero costs” for the hospitalization in case of patients able to be treated at home.

ACKNOWLEDGMENT

This work is supported by a grant from the Ro-manian Ministry of Education and Research, within PN_II programme (www.cnmp.ro/Parteneriate), contract No. 11-067/2007.

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ISSN: 1790-5125 135 ISBN: 978-960-474-110-6

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Real Time Telemonitoring of Medical Vital Signs