Session 6 - 1

FM MODULATED LOW POWER LOW VOLTAGE
TRANSMITTERS FOR IMPLANTS

Mans B. Jansen
Agricultural Research Department (DLO-NL)
Institute of Agricultural and Environmental Engineering (IMAG-DLO)
Mansholtlaan 10-12, P.O. box 43, NL-6700 AA Wageningen, The Netherlands

In the past two years, more research has been carried out on the patented modulation method for small transmitters [1]. For a number of applications, transmitter circuits have been developed which combine very good stability and FM/FSK modulation properties with small dimensions and low current consumption at low supply voltages. These transmitters operate in the 30 MHz and in the 153 MHz telemetry bands. In the paper, several applications will be discussed, each of them tailored to the specific needs of the implants. Special emphasis will be put on the application for the European CAPT project, in which the University of Leuven, Belgium, and the University of Vila Real, Portugal are co-operating.

REFERENCES

[1] Jansen, M.B., Cats, T.A.J. 1996, Designing telemetry transmitters in conformity with the requirements of the Dutch Ministry of Transport, Public works and Water Management. Biotelemetry XIII; 166-171, Proceedings of the Thirteenth Symposium on Biotelemetry, Williamsburg, March 26 to 31, 1995, USA

Session 6 - 2

A NEW IMPLANTABLE MICROPROCESSOR CONTROLLED LONG DISTANCE TELEMETRIC DEVICE FOR CONTINUOUS MONITORING OF ANIMAL ACTIVITY AND TEMPERATURE

Ben Geeraerts(I), Mans Jansen(II) and Robert Puers(I)
(I) Katholieke Universiteit Leuven, Departement Elektrotechniek,
ESAT-MICAS Kardinaal Mercierlaan 94, 3001 Heverlee, Belgium
(II) IMAG-DLO, Postbus 43, 6700 AA Wageningen, The Netherlands

INTRODUCTION :

In the field of animal monitoring there is a great need for intelligent and versatile devices for continuously collecting activity and temperature data of the animal without hampering of the animal and elaborate setups. Hence, the data should be transmitted by means of a "long distance" RF-link to a central personal computer which collects and processes the data. The device described in this paper fulfills all the above criteria.

TECHNICAL DESCRIPTION :

The new device is contained in a glass, laser-sealed cylinder with an external diameter of 17 mm and length of 104 mm. A battery with an energy storage capacity of 1000 mAh powers the two dedicated thick film hybrids with the custom built electronic circuitry. The device can continuously monitor the animal and collect data for up to 1 month, depending on the monitoring window parameters.

The first hybrid is built around the Motorola 68HC11 microprocessor and can store activity and temperature data in a non-volatile 2 kilobyte EEPROM. A piezo-resistive accelerometer is used to sample the activity of the animal. User-defined movement detection algorithms are stored in a 32 kilobyte EPROM for processing of the raw accelerometer samples. A calibrated thermistor provides the temperature data. A low-power timing circuit is responsible for waking up the microprocessor at the appropriate user-controlled time-intervals and limiting of the overall power drain.

The second hybrid consists of a Frequency Shift Keying transmitter with a carrier wave of 30.025 MHz. This is used when stored and processed data is transmitted to the receiver-unit connected to the central personal computer. A Manchester-encoded bitrate of 2 kilobaud can be achieved over distances up to 10 meters, depending upon the external Electro-Magnetic Interference. The transmitter coil is put around the 2 closely stacked thick film hybrids.

CONCLUSIONS :

The new implantable device can continuously provide valuable activity and temperature data of an animal in many practical and research situations. For example, the device is being tried out for the oestrus detection of sows. The "long distance" wireless link and user-definable timing parameters and movement detection algorithms will prove to be a very valuable asset of this device indeed.

Session 6 - 3

NUMERICAL MODELLING OF BODY-ANTENNA INTERACTION EFFECTS IN INTRACORPOREAL UHF RADIO TELEMETERS

W G Scanlon and N E Evans
N Ireland Bioengineering Centre & School of Electrical and Electronic Engineering
University of Ulster, Shore Road, Newtownabbey, Co Antrim, N Ireland, UK, BT37 0QB

INTRODUCTION

Intracorporeal UHF radio telemeters are used for human and animal physiological monitoring in both clinical and research settings. In-body placement governs the resultant output power and polar pattern shape of the radiating system. Both parameters are frequency dependent, and are strongly influenced by body structure and the electrical properties of the surrounding tissue.

Practical determination of body influences is not always feasible since extensive antenna test range facilities are required to implement near and far field electric field strength measurements. Finite-Difference Time-Domain (FDTD) numerical modelling methods, however, allow the accurate determination of all critical parameters affecting in-body antenna performance provided a suitable body model is available.

METHOD

Body models were constructed by segmenting the NIH Visible Human data for the regions directly surrounding the implanted telemeter. A FDTD program was developed using ‘C’; the advantage of this technique is the direct calculation of near-field electromagnetic data and the relatively straightforward generation of radiation patterns.

RESULTS

Representative results are presented below. An electrically small 418 MHz source was placed in the abdomen of an adult male body model. The plot shows the vertical component of the electric field across a transaxial plane.

Software generated body-model Isoelectric field plot

DISCUSSION

The calculated anterior radiation is dominant as the posterior near-fields are non-uniform resulting in a 15 dB power reduction in this direction.

Session 6 - 4

A BIOTELEMETRIC IMPLANTABLE HEART-SOUND RATE MONITORING SYSTEM

Luís Torres-Pereira*, Carla Torres-Pereira**, Paulo C. Ruivo* and Carlos Couto*
*Dept. of Engineering and **Dept. of Biological and Environmental Engineering,
University of Trás-os-Montes and Alto Douro, Apt. 202, 5000 Vila Real, Portugal

INTRODUCTION

We aim to develop a reliable, implantable, biotelemetric, heart-sound rate monitoring system for studies of heart rate variability, causing minimal constraint to subjects. This concept of biotelemetric phonocardiography searches for advantages over electrocardiography in heart rate monitoring: it only requires an encapsulated single sensor probe and pursues the objective of obtaining reliable biotelemetric transmission from subjects moving.

METHODS

Heart sounds arise from heart muscle and valve activity or heart blood flow. Piezoelectric transducers allow the detection on the human chest surface of the acoustic vibration produced by the heart mechanical activity. Taking this into account, we developed a small dimension intelligent capsule with sensor, signal processing and biotelemetric capabilities for heart rate monitoring. The intelligent probe detects each heart cycle, counts the number of cardiac cycles during 7.5 s and sends these data by radio frequency to a personal computer which traces a graph or saves a file of patient heart rate evolution. Due to size constraints, the analog signal processing module was projected to execute as many fuctions as possible with a minimal number of parts. In fact, this module is based on a single four operational amplifier chip, implementing a respiration and movement noise filter, a fullwave signal rectifier, an amplifier with automatic gain control, a second order active low-pass filter, a peak detector, a threshold circuit and a comparator. The AM transmitter module has small size (13 mm x 13 mm x 5 mm) and 418 MHz working frequency.

RESULTS

The digital pulse heart rate signal is obtained comparing the envelope of the heart sound signal with an adjustable threshold. A preset threshold is difficult to optimize and a too low threshold makes the detector sensitive to noise, although it may detect the signal well. This is the case of using an average signal as threshold. The automatic gain control allows the amplifier to self adjust heart sound signal amplification to a level allowing processing. In the circuit used, a change in signal amplitude not only varies amplifier gain but also its threshold. The amplitude of the previous heart S1 pulse determines the new threshold level, thus shortening the adaptation time. Good results were achieved in respiration and movement noise reduction using a passive high pass filter at the first stage of the heart rate detection module.

DISCUSSION

This new heart rate monitoring system relies on the identification of heart sound S1, the most proeminent natural sound signal that occurs during each cardiac cycle. S1 detection is complicated by the wide variation in heart sound morphologies and rhythms, as well as by noise originating from respiration, vocalization, and movement, that may corrupt phonocardiograms. These constraints imply further developments towards a self-adjustable probe selecting and processing heart sounds only.

Session 6 - 6

> > 1 MHZ RF LINKS FOR TWO TYPES OF IMPLANTABLE NEUROSTIMULATORS

DI Stefan Sauermann, Dr. Hermann Lanmüller
Department for Biomedical Engineering and Physics, University of Vienna
1090 Vienna, Waehringerguertel 18-20, Austria

Introduction

High frequency inductive links were developed for two implantable stimulation devices: a telemetrically supplied muscle stimulator and a battery powered miniaturized single channel neurostimulator. This paper describes design considerations and performance of both links.

Methods

Both links use ampitude modulation and passive telemetry to achieve bidirectional data transmission. For the muscle stimulator power efficiency was the main goal. Miniaturization was not of that importance, so the diameter of the receiver coil could be increased appropriately. The final coil diameter was 7 cm. To improve the performance of the passive telemetry the transmitter frequency is crystal-stabilised to 1MHz, although a self-oscillating transmitter would be more power-efficient. Coupling turned out to be high enough for passive telemetry by impedance modulation in the implant. A phase comparator was used to detect the data from the implant.

Passive telemetry in the miniaturized implant was more demanding. The receiver coil has a diameter of 14 mm, inductive coupling to the transmitter is accordingly lower. The amplifiers and filters had to be improved for data detection.

Results

The link for the muscle stimulator has a maximum working distance of 6 cm, 20 mA of current at +/-15Volts can be supplied for the implant circuitry. HF output power can be adjusted by pulse-width modulation. The bidirectional data link works with a standard RS232 protocol at 19600 Baud. The link to the battery powered implant works up to a distance of 4 cm, with 600 Baud. Baud rate for this link can optionally be raised, but a clock rate of 72 kHz was chosen for the implanted microprocessor to minimize its supply current. This restricts the transmission rate to the above value.

Discussion

According to in vitro tests both links have proved to serve their purpose. They are to be tested in animal experiments in the near future. However the transmitter for the muscle stimulator consumes 1 Watt of energy, so warming of the transmitter could become a problem in most unfavourable situations. Further research will be done into power-efficient transmitter design using class E amplifiers and different coil configurations.

Session 6 - 7

IC BASED RF POWERED IMPLANTABLE
TELEMETRY MICROSYSTEM FOR EMG RECORDING

J. Parramon1, P. Doguet2, M. Verleyssen2, L. Leija3, J. Arzuaga4, E. Valderrama1
1CNM parramon@cnm.es, elena@cnm.es
2UCL doguet@dice.ucl.be, verleyssen@dice.ucl.be
3CINVESTAV lleija@mvax1.red.cinvestav.mx
4CCC ccc@netgate.comintur.com.uy

INTRODUCTION This paper presents the development of an implantable telemetric microsystem for recording purposes focusing on the system concept, mixed-mode IC design and packaging. In conjunction with another paper where inductive link design is explored carefully, a new wireless high bit-rate transcutaneous telemetry system is presented including a small size IC-based implant with telemetric and EMG recording circuitry.

METHODS

IC development for implantable microsystems offers a wide range of advantages, like size reduction, high design flexibility and power economy. A 2 microns BiCMOS 5.0 x 5.2 mm2 mixed-mode integrated circuit containing not only the telemetric part (5V regulator, receiver, transmitter, decoder, coder, etc.) but also the application specific part in that case for recording purposes (amplifiers, filters, time multiplexer and A/D converter) is in fabrication. Design guidelines fitted a trade off among area, flexibility and consumption. This chip joins several SMD elements (storage capacitors, RF diodes and coils) to form a hybrid implantable system. The overall size once encapsulated in silastic is expected to be about 1 cm3 including a flat air-cored power coil and a very small cylindrical magnetic-cored transmitter coil. The telemetric system presented here meets the following specifications: (1) bi-directional digital communication with inlink rates at 250 kbps and outlink rates at 500 kbps, (2) outlink PCM, (3) ASK inlink and BPSK outlink modulation, (4) PWM-RZ inlink and outlink bit codification and (5) efficient RF power transference at distances up to 10 mm and lateral misalignment tolerance of ± 10 mm.

RESULTS

A first IC prototype containing some telemetric modules (no recording circuitry) has already been fabricated and successfully tested within a non-implantable telemetric system. A new totally implantable IC here presented has been designed and submitted to fabrication. Test will be covered in early 97 so electronic chip results and telemetric system performances will be available before the ISOB meeting.

DISCUSSION Special efforts on increasing the power efficiency will be taken in future, by introducing an induced secondary voltage closed-loop control and by increasing the integration scale towards submicron structures.

Session 6 - 8

THE DESIGN OF AN IMPLANTABLE TELEMETRIC
DEVICE FOR THE USE IN NEURAL PROSTHESES

Oliver Scholz1, Jordi Parramon2, Jörg-Uwe Meyer1, Elena Valderrama2
1Fraunhofer-Institut für Biomedizinische Technik (IBMT), St. Ingbert, Germany
2Centre Nacional de Microelectrònica, Universitat Autònoma de Barcelona, Bellaterra, Spain

INTRODUCTION

Recent research efforts in neural technology aim at interfacing to the nervous system of living beings. In the case of auditory prostheses, which are already commercially available, this has been implemented successfully. Currently, efforts are directed towards interfacing to the peripheral nervous system for the use in functional nervous stimulation systems (INTER). Concerning the telemetry part of such a device, the challenge lies in the high data rate which is needed for closed loop control multichannel stimulators.

METHODS

Here, the design of a telemetric link is described, which is intended for the use in neural functional stimulation. An implanted, programmable stimulator is to be powered transcutaneously and provided with a bi-directional data link. For this task, an inductive link has been developed, as this is the only choice for a safe energy transmission across the skin and tissue barrier. In contrast to many other neuro-stimulators found in literature, more complicated stimulation pulses than ordinary biphasic rectangular shaped pulses are to be transmitted, giving more flexibility to functional stimulation. This requires higher data rates, which is achieved by using a carrier in the 10MHz range and by implementing data reduction. ASK is installed as a modulation scheme. The transmission distance for this application has been fixed to 10mm. The total size of the implant is determined to be less than 10mm in diameter. The implant coil, which operates without a magnetic core, is therefore restricted to a diameter of 8mm. For the reverse transmission of data, an active transmitter operating at 30MHz with BPSK is implemented. A class-E amplifier powers the external coil.

RESULTS

The telemetric link described here manages a full duplex transmission with 250kbits per second towards the implant and 500kbits per second in the opposite direction. The overall power efficiency of the link is approximately 10% at the specified distance.

DISCUSSION

A functional 10MHz range miniaturized telemetric device for transcutaneous nerve signal transmission has been implemented and tested. Further efforts will focus on enhancing link efficiency and on the final design of a micro implant using a minimum of custom designed chips.

Session 6 - 9

PASSIVE TELEMETRY FOR LOCALIZED
INTERNAL TEMPERATURE MEASUREMENT

Paulo José Abatti, Bertoldo Schneider Jr. & Marcos Santos Hara
Centro Federal de Educação Tecnológica do Paraná
Av. Sete de Setembro, 3.165, Curitiba, PR, Brasil, CEP:80230-901

INTRODUCTION

The aim of this work is to present a localized internal temperature measurement system. The implantable unit, using a thermistor bridge is completely passive, and power and communication are realized using only one external coil.

METHODS The developed system is composed by an implantable unit, an external circuit (in a belt format) and a remote device connected to a computer. The implantable unit has been described previously [1]. Basically, it transmit information (temperature) changing the resonance frequency of two tank circuits, and a third coil is required for powering. In order to allow power and communication using only one external coil (see Fig.1), thus minimizing misalignment problems [2], the external circuit was designed using a time-sharing technique. During about five time constants (t @ 400ms) the external coil is excited using a constant frequency signal (480kHz), powering the implantable unit. After that, during a period of about one time constant (80ms) the external coil is excited using a frequency variable signal (sweep from 600 to 800kHz), allowing the measurement of the internal resonance frequency of the tank circuits. Then, the external circuit digitalize the received information, transmitting it through a omnidirectional 107MHz radio (working range 17m). The remote unit receives and process the signal, sending it through a serial interface to a personal computer. The developed software generates tables, graphs and is able to store the data for posterior analysis.

RESULTS

The measured system sensibility is 0.01ºC. Practical experiments has shown a less then 1% mean error in the 30 to 50ºC temperature range.

DISCUSSION

"In vitro" experiments proved the viability of localized internal temperature measurement, a thermotelemetry system, using a passive implant unit and only one external coil. "In vivo" experiments are planned to be made early in 1.997.

[1] Abatti, P. J. & Schneider Jr., B., 1994, "A Method to Reduce Sensor Bridge Dependence on Loading and Excitation Voltage", Rev. Sci. Instr. 65(3), p 756-757, 1.994.
[2] Soma, M., Galbraith, D. C., & White, R. L., 1987, "Radio-Frequency Coils in Implantable Devices: Misalignment Analysis and Design Procedure", IEEE Trans. Biomed. Eng., BME34(4), p276-282.

Session 7 - 1

CRITERIA FOR COMPRESSION OF BIOSIGNALS AND METHODS FOR DATA COMPRESSION IN ELECTROCARDIOGRAPHY

Chr. Zywietz
Arbeitsbereich Biosignalverarbeitung, Medizinische Hochschule Hannover

Digitized raw-data of biosignals are often very voluminous. For example, a 10 s resting ECG record produces typically an amount of 80 KB, for a three lead Holter electrocardiogram with appropriate digitization 80 to 240 MB of data are generated. Processing this large data volume might result in a small number of measurements and interpretative statements which cover not more than a few hundred bytes.

Since the beginning of biosignal processing data reduction and data compression for storage and retrieval has been subject to research and development and has been discussed in many publications. Various methods, like transformations, linear and non-linear signal approximation, utilization of inter-sample correlation, utilization of stationarity of the signal and other methods have been applied to compress data for transmission and storage.

A major issue is quality assurance and the definition of error tolerances for compressed data. Sometimes only the pre-reservation of diagnostic interpretative statements is necessary, sometimes - particularly in the research environment - the conservation of the original signal is of importance if - with newer, more advanced signal processing algorithms - a re-evaluation of the "expensive" original data is desired.

An overview on recently applied methods for biosignal data compression will be given and problems of typically applied quality indicators like root mean square errors, absolute amplitude differences etc. will be presented and discussed.

With regard to practically implemented algorithms and their application the compression of resting ECGs and the development of the Standard Communications Protocol for Electrocardiography will be discussed in detail. This example will demonstrate how data compression on quasi-stationary periodic signals can be applied: how with consideration of signal frequency content, sample correlation and also with consideration of the clinical needs a quasi optimal compression method has been developed. Also, the method of quality assurance will be described in detail. As a result of this research project an internationally accepted interchange format has been developed and standardized. This interchange format makes possible real-time telephone transmission of the conventional 12 lead ECG and also storage of more than 200 resting ECG on a single 1.44 MB floppy disk.

Session 7 - 2

ECG DATA REDUCTION FOR MEDICAL TELEMETRY SYSTEM

Masaki Kyoso, Akihiko Uchiyama
School of Science and Engineering, Waseda University
3-4-1 Ohkubo Shinjuku-ku, Tokyo, 169, Japan

INTRODUCTION

Many ECG data reduction methods had already been developed in the past twenty years. Although these methods have acceptable compression performance, the total characteristics such as channel noise and power consumption of transmitters are not considered. Since percentage of abnormal waveforms are not so large in case of ECG monitoring, transmitter radiates continuously even if ECG is normal. This leads to signal collision between transmitters and also battery consumption.

METHODS

The data reduction methods we have presented was designed for wireless ECG telemetry system. The transmitter has a simple ECG analyzer which recognizes waveforms are normal or abnormal. If abnormal ECG is detected, full ECG waveforms are compressed with several waveforms prior to detected abnormal ECG. An important parts of the ECG waveforms, such as QRS complex, P wave, T wave are checked and coded with error correcting code. During normal ECG is recognized, data reduction (R-R interval or only heart rate per 30 seconds) is performed. The compression ratio is far better than the other methods, because this algorithm rejects redundancy of data by means of the knowledge of percentage of normal ECG.

RESULTS

The advantages of this method are high channel efficiency, low power consumption, because the percentage of normal data is sufficiently larger than that of full coded transmission. A data reduction of more than expected were obtained in the experiments in both cases of ECG from generator and patient.

DISCUSSION

We have evaluated the performance of proposed system by computer simulation and experiments. Comparison of transmitted and received waveforms of abnormal case showed enough quality for ECG monitor. We can conclude very high compression ratio can be obtained by this method. However, the practical system evaluation is required in hospitals.

Session 7 - 3

TELEMETRIC ECG MONITORING OF
F1 DRIVERS DURING WORLD CHAMPIONSHIP
RACES

Belardinelli A, Ceccarelli R+, Belardinelli A, Palagi G, Ripoli A, Franchi D and Bedini RCNR Institute of Clinical Physiology, Via P. Savi 8, 56100, Pisa, Italy+F1 Minardi Team, Faenza.

A systematic analysis of Formula 1 drivers dynamic ECG during races, for a whole F1 world championship, has been accomplished. The research has been aimed at both the sport-medicine aspect (training and study of the actual driver conditions referring to the specific track) and the investigation of the experimental model of the cardiovascular system standing the high physical and emotional stresses due to the reached velocities, the dangerous conditions and mainly the accelerations otherwise unreachable in other fields (nor in the aerospace one). For example, up to 5 g lateral accelerations can be occasionally reached. The main attention has been paid to the sport-medical aspect and a first methodological approach has been developed in order to support the evaluation of the psycho-physical performance of the drivers. The ECG signal has been collected by a miniaturised and ad hoc developed electrocardiograph and the digitally converted data are stored on the on-board data logger, on-line and/or off-line transmitted through the standard telemetry together with all the environmental and car parameters (velocity, accelerations, position, etc.). The analysis showed that a sizeable physical stress is present, which resulted more relevant than the psychological one. Other interesting correlations have been observed between HR and accelerations. A joined analysis of the HR and the time performance of the driver during the race has been accomplished, giving meaningful parameters of the driver training level.The results of this investigation, in comparison with the data previously collected in other motor sport races and during international marathons, demonstrated, from the sport medicine point of view, that formula one can be considered as a true "endurance" sport.

Session 7 - 4

ECG TELEMETRY EXPERIMENTS FOR EARLY
CARDIAC EMERGENCY TREATMENT

Chr. Zywietz, Medical School Hannover/Germany
D. Assanelli, University Hospital Brescia/Italy
C. Malossi, Elettronica Trentina, Cavareno/Italy

Long term morbidity and mortality of infarcted patients may be reduced if early treatment of acute or hyper-acute infarction can be provided. Preparation of such treatment in an emergency department is supported if the 12 lead electrocardiogram of patients with an acute event/pain can be monitored during transportation to the hospital.

A pre-requisite for this monitoring is the possibility of real time digital transmission of the standard 12 lead ECG from the ambulance car during transportation via telephone line, satellite or radio frequency.

Within two European research and development projects - Standard Communications Protocol for Computerised Electrocardiography (SCP-ECG, AIM 1015) and Open European Data Interchange for Processing of Electrocardiograms (OEDIPE, AIM 2026) of the European Advanced Informatics in Medicine program a methodology for high compression of ECGs with defined (restricted) error tolerances has been developed. Typically a standard 12 lead ECG record for computerised evaluation consists of 10 sec of data resulting in 8 KB/sec of data. During the SCP ECG project transmission protocols and compression methods have been investigated extensively. As a result a compression a scheme was developed which requires the transmission of 4 to 7 KB of data per 10 s record. This allows the reconstruction of the original ECG with an RMS error of £ 10 µV RMS and a peak error of not larger than 100 µV.

The error restriction ensures that clinically important detail information (e.g. atrial fibrillation versus atrial flutter) is maintained. The practical applicability of the SCP-ECG protocol has been demonstrated within the OEDIPE project.

Compressed 12 lead ECGs can be transmitted in real time at transmission speeds of 9.6 Kbit/sec. After the SCP ECG project and during the OEDIPE project a computer electrocardiograph has been developed which is capable of direct interconnection (dialling + modem communication) via the telephone network to a host computer within the emergence department. There the transmitted ECG is reconstructed and can be monitored.

Various transmission experiments from a resting and moving ambulance car have been performed in Brescia and in Hannover to analyse the practicability of this approach. The experiments have shown that a transmission speed of 9600 bits/sec can not always be reached during the major business hours within the analogue telephone network. Establishment of connection and a transmission with reasonable low error frequency requires sometimes the reduction of the transmission speed to 2400 bit/sec. There is on the other hand no problem with transmission speed if ISDN connections can be used. In summary: a data compression method and a communications protocol for real time telephone transmission of standard electrocardiograms have been developed which allow a real time monitoring via telephone line if a transmission speed of at least 9600 bit/sec can be provided. A real-time telemonitoring of the full standard ECG provides the basis for improved cardiac emergency care with earliest treatment of acute infarctions.

Session 8 - 1

ABPM - USEFUL TOOL IN
MANAGING ARTERIAL HYPERTENSION

Bernd Krönig
Dept. of Internal Medicine, Ev. Elisabeth Hospital, Theobaldstr. 12, D-54292 Trier

A

mbulatory blood pressure monitoring (ABPM) is mainly applied in a non-invasive manner with intermittent blood pressure (BP) recordings every 15 min. in day-time and every 30 min. in night-time. The great number of at least 50 reliable readings per 24 hours helps to get a better insight in the BP-situation under every-day conditions, compared to casual BP´s (CS) and self measurements (SM).

ABPM has turned out to be the best method in evaluating

> > - diagnosis,
> > - treatment, and
> > - prognosis

of hypertensive patients. In diagnosis, patients with white coat hypertension (WCH), reverse WCH, impaired day-night-regulation, paroxysmal hypertension, and inadequate response to physical / emotional stress can be filtered out by ABPM. About 25 % of patients being hypertensives by by CS (so-called WCH) are normotensive in ABPM (=BP means in day-time < 135/85-, at night < 120/70-, and for 24 hours < 130/80 mmHg), showing only a somewhat steeper rise of the wakening BP. Vice versa, there are some patients (about 8 %) having already signs of secondary organ damage (e.g. LVH) with elevated ABPM in day-time, but still normotensive CS (so-called reverse WCH).

Regarding the day-night BP-regulation there are a great number of patients with advanced essential hypertension and probable history of stroke, myocardial infarction, resp. diabetes mellitus, who show a so-called "non-dipper"-constellation (= BP fall < 10 % / < 15 % for systolic and diastolic means during the night). Among the small population (<5%) of patients with secondary hypertension about 2/3 are "non-dippers".

Drug treatment may best be controlled by ABPM, since the individual duration of action with the aim of a 24-hour normotensive BP profile can be evaluated thoroughly. In our experience, quite a number of patients needs therefore an additional medication either at noon, at night, or even in the early morning, before getting up.

From the prognostic standpoint of view ABPM is superior to CS and SM, showing better correlations to LVH, cerebrovascular damage, and e.g. microalbuminuria. If the additional parameter "blood pressure variability", estimated by the standard deviation of interval BP means, has any progrnostic implications, is not yet settled.

In conclusion, the easily applied ABPM should be used as a routine method in every hypertensive patient, giving the most valuable results in respect to diagnosis, treatment, and prognosis of the disease, compared to casual and self-measured blood pressure.

Session 8 - 2

NOCTURNAL HYPERTENSION

L. Grote
Medizinische Poliklinik, Philipps-University, Marburg, Germany, Baldingerstrasse,
35033 Marburg

The physiological drop in arterial blood pressure during the night has been known since the beginning of this century. The so called 20% "dipping" in systolic and diastolic blood pressure occurs in healthy subjects and also in the majority of hypertensives. Since longterm blood pressure recordings have been performed, it has been seen that some patients have a lack in this physiological drop. This pattern of 24 hour blood pressure is known as nocturnal hypertension or "non-dipping" and is frequently seen in secondary hypetension. Therefore, it is taken as an important diagnostic marker in this disease of low incidence.

In the last decade new insights have ben given in this field. The use of ambulatory 24 hour blood pressure monitoring in general practice and clinical settings have shown that "non dipping" is more frequent than before and it is related to an increase in cardiovascular risk. Stroke und left ventricular hypertrophy are linked more to Non-Dipping and females are more often susceptible than males. Also, it has been shown, that 24 hour blood pressure is altered by sleep related autonomic dysfunction for example sleep apnea and snoring.

In this lecture, the main methodological problems are discussed. Blood pressure monitoring during sleep can disturb sleep architecture. Therefore, blood pressure increases are induced. Also, insomnia and dysomnia can alter blood pressure. Study results from the comparison of continuous and discontinuous blood pressure monitoring are presented. It has been shown, that they can not follow the high blood pressure variability in autonomic dysfunction during sleep. The method of continuous non-invasive blood pressure recordings by Penaz has problems with calibration procedures and also disturbs sleep.

In Conclusion: The knowledge about blood pressure during the night and during sleep has improved. The clinical relevance of 24 hour blood pressure monitoring has been demonstrated. Methodological problems and limitations in some techniques have to be taken into consideration to distinguish between artefacts and haemodynamically significant and therapeutically important blood pressure elevations during the night and during sleep.

Session 8 - 4

PROGNOSTIC IMPLICATIONS OF ABPM

PD Dr.Peter Trenkwalder
Department of Internal Medicine, Starnberg Hospital
Ludwig Maximilian University Munich
Osswaldstr. 1, D - 82319 Starnberg, Germany

INTRODUCTION

Numerous epidemiological studies have demonstrated that high blood pressure (BP) values are closely correlated with an increased cardio-vascular and cerebrovascular morbidity and mortality. In long-term intervention trials treatment of hypertension with antihypertensive agents could reduce the cerebrovascular event rate by 35-40% and the cardiac event rate by 15-20%. All these studies have been performed with office BP measurements. In the last decade ambulatory blood pressure monitoring (ABPM) with modern portable devices has become available world-wide. Actually the question remains, whether the increased information provided by ABPM (e.g. about the total circadian BP profile) can better predict hypertensive complications and whether treatment guided by ABPM will improve the outcome of hypertensive patients.

REVIEW DATA

More than a hundred cross sectional studies studies have shown that 24 hour ABPM is a better predictor than office BP for surrogate markers and true target organ damage of hypertension such as left ventricular mass and wall thickness, arterial wall thickness, systolic and diastolic left ventricular dysfunction, proteinuria (including microalbuminuria) in patients with diabetic or hypertensive nephropathy, retinopathy, brain damage and an overall organ damage score. Only few prospective studies using ABPM are hitherto available: Perloff et al. demonstrated more cardiovascular events in patients with both increased office and ambulatory BP, Verdecchia et al. showed an increased event rate in hypertensives with impaired day-night rhythm, Mancia et al. reported a close correlation between drug-induced regression of left ventricular mass and changes in ambulatory BP.

ABPM can easily diagnose the „white coat effect", i.e. the raise in BP during clinical visits, and „white coat hypertension", i.e. increased BP in the office compared to normal BP during the remaining day. Whether white coat hypertension is a pure benign disorder without increased risk or a borderline stage between normotension and hypertension remains to be determined.

CONCLUSION

ABPM improves diagnostic categorization of hypertension and evaluation of target organ damage. Future prospective long-term studies must determine whether diagnosis and treatment based on ABPM (in addition or instead of office BP) will finally improve the prognosis of hypertensive patients.

Session 8 - 6

NON-INVASIVE BLOOD PRESSURE MEASUREMENT APPROACH FOR CONTINUOUS AMBULATORY MONITORING

Ripoli A, Franchi D, Palagi G, Belardinelli A, Ghione S and Bedini R
Institute of Clinical Physiology, National Research Council,
Via P. Savi 8, 56100 Pisa, Italy.

The continuous non-invasive monitoring of blood pressure is an up to now unresolved problem. The available devices based on vexing occlusive cuffs are not suitable for long-time measurements, while the compressor noise causes an emotional artefact on the measurement itself. As a promising measurement method, avoiding the above mentioned problems, we investigated the relationship between the pulse wave velocity, namely the distance that the pulse wave travels in one second, and the systolic, diastolic and mean values of blood pressure. The greatest simplicity in the measurement is accomplished evaluating the pulse wave velocity by means of the delay between the R wave of the electrocardiogram and the onset of the pulse wave in a peripheral site. Although such a method has been already exploited, supposing pulse wave velocity to linearly vary with blood pressure, an explicit relationship between these two physiological parameters, being the velocity of the pressure wave a function of several parameters of the cardiovascular network (mainly the dimensions and the stiffness, the Young's modulus, of the vessels), has not yet been identified. In order to study the behaviour of the pulse wave velocity we built a mathematical model of the arterial network, so that an evaluation has been possible about the effect of blood pressure, age and body weight on it. The data for the model has been acquired, during cath-lab sessions, by means of an ad hoc developed computerised acquisition system of blood pressure waveform and pulse wave velocity. The pulse wave has been detected by means of transmission photo-pletysmographic device while the aortic pressure waveform is acquired by means of a fluid-filled pressure transducer, being our main interest on man systolic and diastolic values of blood pressure and not on its exact waveform The signals, acquired at a sampling frequency of 2000 Hz, to assure the necessary time resolution, and on-line displayed are: one lead ECG, pulse wave and aortic pressure. An algorithm has been developed for the delay evaluation between the QRS complex and the pulse wave onset; beat to beat systolic, diastolic and mean aortic pressure values have been carried out. The accomplished analysis showed an increasing in the pulse wave velocity with the pressure values, while the already exploited linear model seems not to fit the acquired data. A new estimation is here provided by means of a developed non-linear model calibrated, by means of alternative blood pressure measurements, on the single patient, while special care has been paid in the selection, for the photo-pletysmographic device, of a distal peripheral site, in order to minimize the error induced by the isovolumic contraction period of the heart.

Session 9 - 1

DAILY AND SEASONAL PATTERNS OF HEART RATE
AND ACTIVITY IN ROE DEER AND RED DEER
WITH RESPECT TO ENERGY EXPENDITURE

Franz Schober, Susanne Reimoser
Research Institute of Wildlife Ecology, Vienna Veterinary University,
Savoyenstrasse 1, A-1160 Vienna, Austria

INTRODUCTION

As a part of investigations on time and energy budgets of roe deer (Capreolus capreolus) and red deer (Cervus elaphus) biotelemetric long-term studies of heart rate (which is highly correlated to relative changes in energy expenditure) and activity in both species were carried out.

METHODS

Animals were equipped with implanted heart rate and activity transmitters and held in a fence close to natural conditions. On roe deer a direct transmission (150 MHz) from the implant to the receiving station was applied, using pulse-interval modulation (for QRS detection) and pulse-duration modulation (for activity detection). On red deer a repeater system consisting of an implantable heart rate transmitter (100 kHz) and an extracorporal repeater collar (150 MHz) was used. In the receiving stations data were preprocessed on a minute basis. For detection of animal's activity the mean heart rate, the number of head-up/down changes and the number of rf signal strength variations have proven to be sufficient. An algorithm for activity detection was established experimentally and verified by simultaneous video observations. Special efforts were made to check the non-reactivity of the biotelemetric method on the behaviour of the animals.

RESULTS

No difference in behaviour could be detected after day 13 post operationem compared to the behaviour before the surgical procedure. The correlation coefficient of measured and observed activity was 0.90. The mean portion of time, classified wrong (active/inactive or vice versa) during 10 days of observation was 7.6%. Detailed daily and seasonal activity and heart rate patterns are presented using the data of 16 roe deer and 12 red deer. Roe deer shows various sex-specific seasonal fluctuations of heart rate (energy expenditure) related to their biological rhythm. Red deer shows a very strong decrease in heart rate during the winter (about 60 to 50 % of the summer values).

DISCUSSION

This paper gives an example for the versatility of biotelemetric studies on wildlife animals. Since "inactivity" (lying) was detectable very reliable with this method, all heart rate values related to inactivity delivered patterns of "resting heart rate" which are very important for the investigation of seasonal changes in energy expenditure.

Session 9 - 2

RECORDING THE WATERING BEHAVIOUR
OF FREE RANGING PRZEWALSKI HORSES
(EQUUS PRZEWALSKII POLJAKOV, 1881) IN
A SEMIRESERVE

Scheibe, K.M.; Eichhorn, K.
Institute for Zoo Biology and Wildlife Research Berlin
PF 1103
10252 Berlin

INTRODUCTION

Przewalski horses lived originally in an arid environment. They were certainly adapted to shortage of water. Information about the watering behaviour of zoo-born animals and individual variation may be substantial for the reintroduction of that species into natural habitats.

METHODS

The watering behaviour of twelve Przewalski horses was recorded continuously over 17 month in a semireserve. A narrow access path to the watering point could be used by one animal only at a time. When an animal entered the path, it was identified from an identification station fixed to the side wall through an external collar-mounted transponder attached to each of the animals. The amount of water consumed from an automatic water bucket was measured by an electronic water counter. Also contained in the installation was an electronic balance. Results were recorded by a PC and were saved together with time of day and date in monthly dBase format files. Air temperature was continuously measured and was recorded by the same PC that was used for water registration. The data files were analysed for individual frequency of drinking and the amount of water consumed.

RESULTS

Individual variations in water consumption and drinking frequency were significant throughout the observation period. Three individuals formed a top group for mean water consumption and frequency of water uptake. On the other hand, two animals obviously were representative for low consumption and low frequency of drinking. Individual differences were more clearly detectable in dry periods and hot weather. The mean daily water uptake by all animals was influenced by the dry matter content of the forage and by air temperature. Water consumption was higher in warm periods but also in dry periods if the latter coincided with cold weather.

DISCUSSION

Mean daily water consumption by most of the observed Przewalski horses was relatively low, as compared to domestic horses. Individual differences can not be explained completely jet. Meanwhile, it seems to be reasonable to select individuals with low water demand for reintroduction to the natural habitat to avoid unnecessary suffering, loss and failure.

Session 9 - 3

THE DESIGN OF A TRANSMITTER FOR
ANIMAL VOCALIZATION

Detlef Burchard, Dipl.-Ing.
Electronic Laboratory
P.O.Box 14426, Nairobi, Kenya

The paper describes the physiological and technical basics for development of a transmitter for acoustical events and gives one example of such a design.

The electro-acoustical channel has to transmit - without undue alteration - a certain audio frequency spectrum and sound pressure range. Both are depending on the vocalization ability of the species under observation. Alteration means linear and nonlinear signal as well as envelope distortion. The channel shall behave well-defined in case of out-of-range signal: Too low or too high sound pressure, frequency or transients.

The components of the transmitter contribute in different ways to the overall performance: The microphone might determine the system noise and the highest undistorted signal level, the amplifier might be designed to limit the frequency range to what is necessary, the compander might be incorporated to increase the dynamic range at the same time be the cause of significant envelope distortion, the modulation method might determine the high frequency bandwidth together with the modulation gain and the generated high frequency power and the aerial efficiency certainly have to do with the transmission range. The capacity of the battery thus, the lifetime of the transmitter, is related to the volume and weight of the pack which has to be in a certain relation to the animal's size and weight. The transmitter must not interfer with other radio frequency services thus has to be electro-magnetic compatible.

These interdependences are discussed on the example of a transmitter designed for spotted hyena (crocuta crocuta) and details given on component values and manufacturers so that the design may be reproduced in an institute's workshop. The result is a reliable transmitter with excellent signal quality and a good chance to obtain postal approval. Other details covered are pc-board, casing, receiving station, reception aerial, simultaneous visual observation, data storage and commentary recording.

Meaningful extensions of the design are possible: Higher dynamic or frequency range, more rf-power and longer battery life.

Session 9 - 4

Long-Term Telemetric Recording and Computer
Analysis of Colonic Motility in Unrestrained Pigs

J. McRorie1, W. Mills2, E. Konigsberg2, and M. Hastings3,
The Procter & Gamble Company, Mason, OH1, Konigsberg Instruments, Pasadena, CA2, and Data Integrated Scientific Systems, Pinckney, MI3

Introduction

The mammalian large intestine is responsible for the mixing, dehydration, storage, transport and evacuation of luminal contents. The motor events that facilitate these activities are poorly understood. This is due, in part, to the low frequency and high variability of colonic motor events. Colonic motions are so slow, and recur at such long intervals, that they may not be fully appreciated by the short term observations usually used to study them. Recent advances in self-contained 'data loggers' have facilitated longer (24 hour) recording periods in ambulatory subjects, but their limited memory capacities require slow sampling rates (1 Hz), and data are inaccessible while recording. Extended monitoring of colonic motility in unrestrained, ambulatory subjects requires an extremely durable solid state probe and telemetric recording device, and a computer system providing continuous acquisition, a sampling rate enabling digital reconstruction of analog events, artifact filtering, analytical interpretation, and adaptability to signal changes.

Methods

The aim of this study was to develop a method for extended term monitoring and high resolution analysis of colonic motility in unrestrained, ambulatory Yucatan mini pigs. We have developed a versatile telemetric recording system (Konisberg Instruments: custom-built motility probe, amplifier/telemetry transmitter, and base station receiver/decoder), coupled with a computer analysis program (Data Integrated Scientific Systems), capable of high sampling rates, virtually unlimited memory (optical disc), and on-line (monitor and laser printer) observation and analysis of motility. Three female Yucatan mini pigs had a cecal fistula created by surgically attaching the cecum to the abdominal wall. The pigs have been maintained for >3 years without serious health problems.

Results

Colonic motility was recorded continuously in the proximal colon for up to 6 consecutive days using a motility probe with 5 solid state pressure transducer ports. A baseline of motility values and patterns has been established from sixty three 24-hour recordings for the proximal colon of the pig. Non-propagating motility was the predominant motor activity, and was observed as either random events (87% of recorded non-propagating events) or in a '3 contractions per minute' (3 cpm) pattern (13% of recorded non-propagating events). Propagating contractions were also observed, and represent approximately 6% of all recorded pressure events.

Discussion

The data acquisition rate of this system allowed for the identification of propagating contractions with rates up to 16cm/s, not previously described in the literature. The relatively high frequency (27.9 + 2.6/24 hours), high velocity (4.9 + 1.7cm/s), low amplitude (31.2 + 0.9mmHg), and short duration (7.8 + 0.9s) of these rapidly propagating contractions suggest they may act on a lower viscosity substrate, such as gas.

Session 9 - 5

TELEMETRIC OBSERVATIONS OF CIRCADIAN
RHYTHMS OF BODY TEMPERATURE IN SPINY
MICE (ACOMYS) LIVING IN THE JUDEAN
DESERT OF ISRAEL

R.ELVERT, G.HELDMAIER
Fachbereich Biologie / Zoologie, Philipps-Universität, D - 35032 Marburg

INTRODUCTION

Trapping data have shown that the common spiny mouse (Acomys cahirinus, 30-45g) is active during the night, as are the most desert rodents, whereas the golden spiny mouse (Acomys russatus, 45-65g) is active during the day when coexisting in the same habitat (Shkolnik A 1971: Int J Biometeor, vol 15, number 2-4, 115). When A. cahirinus is absent from the habitat A. russatus shows a nocturnal pattern, too. We investigated body temperature rhythms (Tb) in a mixed population of both species in Ein Gedi Nature Reserve, Israel.

METHODS

The habitat of the spiny mice in Ein Gedi is characterised by steep rocky mountain escarpments running parallel to the Dead Sea. Huge blocks alternate with small boulders. Shaded caves rises which are ideal living space for these mice. On a rocky hill slope of about 5000m2 mice were trapped with 50 collapsible Sherman box traps and marked. Animals were implanted with temperature transmitters, developed by Oekokart E&V in Munich, into the abdominal cavity. With different fixed frequencies the transmitters sent signals in intervalls correlating with the Tb. Two antennas received the signals which were recorded by a tracking receiver (B+R, Freiburg) and transfered with an interface (Datalog, Moenchengladbach) to a computer. A special developed software checked the transmitters every 4min. Ambient temperatures (sun, shade, beneath a rock, in the measure box) were measured with thermocouples and stored in a data logger (AMR, Holzkirchen) parallel to the Tb. Solarpanels supplied the system with energy (Elvert et al 1996: Verh Dtsch Zool Ges, vol 89.1, 144).

RESULTS

A.cahirinus showed an obvious rhythm of Tb, corresponding to a rhythm of a nocturnal animal in its natural habitat. Until now such circadian rhythms have only been shown under natural photoperiod in the laboratory (Kronfeld N et al 1994: Israel Journal of Zoology, vol 40, 177). In the activity phase during the night Tb rose to 37.5°C. During the day the temperature dropped to 34°C. The rhythm of Tb was detected in all four seasons. During the hot season Tb of A.russatus varied between 33 and 39.5°C, suggesting a bimodal temperature rhythm with maximal values in the morning and in the evening. In winter A.russatus showed no detectable rhythm in Tb. Body temperature varied between 36.5 and 37°C.

DISCUSSION

These results point out that the activity during the day seems not connected with a phase shift of Tb to a rhythm of a typical diurnal animal. This might represent an adaptation to very high ambient temperatures.

With the supportment of the GIF (German Israelian Foundation)

Session 9 - 6

CHRONIC CARDIOTOXICITY OF DOXORUBICIN
MEASURED BY TELEMETRY IN MICE

K. Kramer, S.A.B.E. van Acker, J.A. Grimbergen, W.J.F. van der Vijgh and A. Bast. Leiden/Amsterdam Center for Drug Research, Division of Molecular Pharmacology, Department of Pharmacochemistry, Vrije Universiteit, Amsterdam, The Netherlands.

Oxygen free radicals play a role in the cardiotoxicity of doxorubicin (Dox). The clinical use of Dox is limited by a cumulative dose-related cardiotoxicity. In laboratory animals, histology is most commonly used to study Dox-induced cardiotoxicity, in combination with biological and functional parameters. However, for monitoring during treatment, a large number of animals is needed. In literature, there are several reports on electrocardiogram (ECG) changes after chronic Dox-administration in anaesthetized laboratory animals. Recently, we developed a new method to measure ECG in freely moving mice by telemetry (1). With this model, we investigated the effect of chronic Dox administration on the ECG of freely moving Balb/c mice equipped with a telemeter and the efficacy of ICRF-187 as a protecting agent. The mice were given 6 weekly doses of 4 mg/kg doxorubicin intravenously and, when appropriate, 50 mg/kg ICRF-187 intraperitoneally one hour prior to Dox administration. After 6 weeks the ST-interval in Dox-treated mice had widened significantly, however in ICRF-187 co-mediated mice there was no significant difference in the ST-interval compared with the control animals. These data were confirmed by histology since it was found that the histological scores per individual mouse correlated very well with the increase in ST-interval (r=0.902). In conclusion, the ECG measured by telemetry can be considered as a valuable and sensitive tool for measuring cardiotoxic effects of anticancer agents and the effect of protectors by monitoring the animal during treatment. In addition, telemetry makes it possible to monitor without introducing interfering factors and saves animals and time compared with histology.

References
1. Kramer et al., J. Pharmacol. Toxicol. Meth. 1993, 30(4), 209-215.

Session 9 - 7

TEMPORAL DYNAMICS OF THE
CARDIOVASCULAR AND THERMOGENIC RESPONSE
TO SOCIAL STRESS IN RATS.

Sietse F. de Boer, Andrea Sgoifo, Peter Meerlo, Bauke Buwalda, and Jaap M. Koolhaas.
Department of Animal Physiology, University of Groningen
P.O. Box 14, 9750 AA Haren, The Netherlands.

INTRODUCTION

Epidemiological studies in humans emphasize that major uncontrollable psychosocial stressors are important precipitating/predisposing factors in the development of affective (anxiety, depression) and somatic (cardiovascular) disorders. A striking aspect of these ilnesses is that both the symptoms and the responsivity to pharmacological treatment evolve over time, even remarkably long after the preceding stressful event. However, few animal models of affective disorders have considered the time course of stress-induced changes in behavior and physiology.

METHODS

In our experimental approach in male rats we focus on the analysis of the temporal dynamics of the behavioral, physiological and neurochemical consequences of a single, 60 min lasting social defeat by a dominant male conspecific. The animals are provided i.p.with a small biotelemetric transmitter (DSI) for continuous chronic recording of ECG, heartrate, bloodpressure, temperature and activity using DSI Labpro acquisition and analysis software.

RESULTS

As part of the classical response to an acute stressor, the social defeat induces strong behavioral (defense) reactions and associated physiological (tachycardia, hypertension, hyperthermia), neuroendocrine (increased corticosterone, catecholamine, prolactin, testosterone) Most of these responses diminish within minutes to a few hours after termination of the social stressor. However, more sustained recordings indicate that social defeat induces changes in various behavioral and physiological parameters each of which may have different course in time ranging from several days to weeks. During the first 7-14 days after the event, there is a decrease in general activity, growth, sexual interest and open field exploration as well as a reduction in the circadian variation of body temperature, heart-rate and blood-pressure. In addition, behavioral provocation tests show a gradually developing and long-lasting (at least up to 5 weeks) enhancement of behavioral (immobility reaction to sudden silence) and physiological (sudden-silence evoked bradycardia and handling/novelty-induced hyperthermia and tachycardia) responsiveness to mild environmental stimuli.

DISCUSSION

These long-term temporal dynamics of the social stress responses and its consequences may provide an important fundamental approach of the etiology and symptomatology of stress-related disorders.

Session 10 - 1

SPAWNING MIGRATION OF SEA TROUT
(SALMO TRUTTA TRUTTA) IN THE LOWER
RHINE, THE NETHERLANDS

Abraham bij de Vaate1 & André W. Breukelaar2
Institute for Inland Water Management & Waste Water Treatment
1 P.O.Box 17, NL-8200 AA Lelystad, The Netherlands
2 P.O.Box 9072, NL-6800 ED Arnhem, The Netherlands

INTRODUCTION

An important aim in the ecological rehabilitation of the River Rhine is the reintroduction of anadromous fish species like Atlantic salmon (Salmo salar), which was extincted from the river Rhine in the first part of this century. This species spawns in Germany and France. The Lower Rhine only serves as a migration route. In the last decades spawning migration possibilities of anadromous fish in general have been drastically reduced as the result of river engineering in the Lower Rhine. Unknown is the effect of physical obstacles constructed, specially in the delta area. By the absence of Atlantic salmon, Sea trout (Salmo trutta trutta) was selected as a representative species in this study on spawning migration possibilities for the Atlantic salmon. Sea trout density in the river increased considerably due to water quality improvement from the 1970's.

METHODS

Mature sea trout is tagged, on several locations in the Dutch coastal area of the North Sea, with tags of the transponder type. Taged animals are released on the same spot were they were caught. The tags only transmit a signal when activated for a short time by an interrogation signal. This signal is picked up when passing fixed detection stations along possible migration routes. The telemetric system used in this study is the so-called NEDAP TRAIL system. Its technology is based on inductive coupling between an antenna loop on the bottom of a river or canal and a ferrite rod antenna as part of the transponder.

RESULTS

Sea trout tagging started in December 1996. At least 200 specimens of mature Sea trout are expected to be tagged before March 15, 1997. Background information and first results of the study will be presented.

DISCUSSION

The NEDAP TRAIL system is a new technique in fish migration studies based on telemetry. In general systems being used are based on two principles of signal transmission: acoustically or via radio waves. Both radio and acoustic tags could not be applied. Conductivity in the River Rhine varied between 32-139 mS/m (1987-1994), which was considered to be too high for optimal functioning of radio tags. Intensive shipping (on average every two minutes a vessel passes the German-Dutch border) was the reason that acoustic tags could not be applied, because background noise of shipping interferes the acoustic signal too much.

Session 10 - 2

DIURNAL SWIMMING PATTERNS OF WHITETIP
REEF SHARK, TRIAENODON OBESUS, AS
OBSERVED BY BIO-RECORDER SYSTEM

Kazunari Yano*, Osamu Abe*, Yoshitake Takada*, Minoru Toda**, and Senzo Uchida**
*Seikai National Fisheries Research Institute, Ishigaki Tropical Station,
Fisheries Agency of Japan, 148-446 Fukai Ota, Ishigaki, Okinawa 907-04, JAPAN
**Okinawa Expo Aquarium, 424 Ishikawa, Motobu-cho, Okinawa 905-03, JAPAN

INTRODUCTION

Whitetip reef shark, Triaenodon obesus, is a common species of tropical inshore of the continental shelves and island terraces, frequently found near the bottom, resting in caves or under coral ledges during daytime. The whitetip reef shark appears to have a narrow home range, moving within a radius of only a few kilometers. This study presents the diel swimming patterns of captive whitetip reef shark in swimming tank of an aquarium, which were measured by bio-recorder system.

MATERIALS AND METHODS

Adult-size whitetip reef shark, Triaenodon obesus, was captured in a swimming tank of the Okinawa Expo Aquarium and was used in the present study during from 3-24 December, 1994. The diel swimming patterns of whitetip reef shark were measured with a time-depth recorder and time-illumination recorder (bio-recorder system, 18 mm in diameter, 109 mm in length, 284 g in air, and 3.5 g in water). The time-depth and time-illumination recorders were attached to first dorsal fin of the shark.

RESULTS AND DISCUSSION

This reef-associated shark was usually found near the bottom, sometime resting in caves or under coral ledges-like areas in the swimming tank during the day. This study indicate that it is more active at night. The diel swimming patterns are probably adapted to feeding behavior, particularly active swimming in home range areas during nighttime and crevices and holes in the coral during daytime, where it catches small fish, crustaceans and octopus.

Session 10 - 3

A RADIO-ACOUSTIC POSITIONING
AND TELEMETRY NETWORK

Ron O'Dor
Dalhousie University
Biology Dept., Halifax, NS, Canada B3H 4J1

INTRODUCTION

Radio-linked Acoustic Positioning and Telemetry (RAPT) systems, now in commercial production by Vemco Ltd., Shad Bay, NS, are rapidly finding a wide range of applications around the world. A major advantage of RAPT is that range limitations of the smallest acoustic transmitters on small animals can be offset by saturating an environment with radio buoys that relay acoustic arrival times to a ship or shore base station which triangulates positions and decodes telemetered data. Many critical questions for marine populations require information about the ranges and behaviours of early life history stages obtainable only with the most advanced RAPT systems, using large numbers of buoys to follow tiny transmitters over large areas.

METHODS

Initial demonstrations of such systems could best be done by sharing buoys among research groups, but this is hampered by: 1) lack of an international standard for frequencies for this technology, 2) variation in rapidly developing hard- and software, 3) constraints on current software.

RESULTS

We propose establishing a user consortium or network to pursue common goals such as international frequency standards and to establish priorities for hard- and software development. This will insure maximum interchangeability, minimize development of redundant or unique application approaches and optimize research output and investment. The Dalhousie telemetry group currently holds several grants for developing this technology, is in contact with 25 user groups in six countries and is strategically located near Vemco to organize such a network. We intend to maintain an emailing list and a Web site for exchange of ideas, requirements and experiences - essentially an online user's manual. It is important to restrict some operational parameters for compatibility but equally important that these restrictions do not eliminate major applications at this early stage of development. The presentation will briefly survey historical applications of RAPT from the first implementation (Nelson & McKibben. 1981. In Proc. 3rd Internat. Conf. Wildlife Biotelemetry) to the prototype for the current system (O'Dor et al. 1989. In Proc. 10th Internat. Symp. Biotelemetry) to a recent 3D study (Sauer et al., In press. Biol. Bull.). It will discuss approaches under consideration, as well as the range of anticipated future improvements and collaborative developments. Critical issues, for example, are the best way to move fluidly between triangulating cells and the tradeoffs between GPS and acoustic self-positioning for buoys.

DISCUSSION

These issues need collective consideration because they fix hardware in ways that may rule out certain applications. The ISOB should provide a valuable forum for airing such questions. I will also outline the state of the network at the time of the symposium.

Session 11 - 1

ETHOLOGICAL AND ECOLOGICAL
CHANGES IN BIRD TELEMETRY

Hans-Wolfgang Helb
University of Kaiserslautern
Working Group Biology and Ecology
Germany

Birds are world-wide a favourite and interesting group of animals and there is often an emotional relationship between humans and birds. However, they may also function as important bio-indicators used to support nature conservation schemes.

One way to use them is in telemetric studies. With the help of this technique, in which birds are monitored using small radio transmitters, we can gain detailed insight in the behaviour and ecology of the birds in the vicinity of settlement as well as in remote areas such as forests, lakes, mountains and the sea.

Using this technique remotely we can look at a big number of different parameters. For example we can get information on the birds spatial distribution and habitat, on their diurnal activity pattern (when do they feed, sleep, ...) and also on their interaction with their pair partner and neighbours. Also their migration including breaks can be monitored from the distance.

In addition with optical control of individual birds telemetry also allows us to investigate physiological functions and dynamics of the organism together with factors of the surrounding environment. This will enable us to detect natural as well as man-made disturbances of the birds and to determine the impact on the birds.

All results will help to define pollution factors and give us means for a successful pollution control and wildlife management. This will have a positive influence not only on our co-creatures, but also on us humans.

Session 11 - 2

VHF-TELEMETRY OF HUMBOLDT
PENGUIN FORAGING ACTIVITIES
IN NORTHERN CHILE

Boris M. Culik and Guillermo Luna Jorquera
Institut fuer Meereskunde
Duesternbrooker Weg 20, D-24105 Kiel
Email: bculik@ifm.uni-kiel.de

INTRODUCTION

VHF-telemetry was used on Humboldt penguins (Spheniscus humboldti) breeding at Pan de Azucar Island (26°S, 70°W), Northern Chile, in order to determine a) the area utilization of the birds when foraging at sea, b) the dive duration during travelling and feeding dives, c) travelling speed of the birds, and d) whether birds return to specific areas on subsequent days.

METHODS

Humboldt penguins were equipped in November 1994 (n=5 birds) and in November 1995 (n=8 birds) with streamlined Telonics MOD 225 transmitters. The birds were anaesthetised at the nest site to minimize stress while being handled, and the transmitters attached to the feathers on the back, below the line of maximal girth. Directional receiving antennas (null peak) were placed at approx. 3km and 4km to the North-East and South- East of the breeding island on the main land, at 230m and 350m elevation, respectively. Antennas were manned for 8h per day.

RESULTS

We obtained 2710 positions (1995) of the birds at sea, 95% of which were within a radius of 22 km around the breeding island. The data allow a detailed analysis of the area utilization of breeding Humboldt penguins from Pan de Azucar Island, as well

as the determination of travelling speed, dive duration, time spent in certain areas and day to day variations in feeding area utilisation.

DISCUSSION

In a previous study, we utilised satellite transmitters to determine where Humboldt penguins from Pan de Azucar Island forage (Culik and Luna, Mar Biol, 1997). The present study served the purpose to increase sample size and spatial resolution. The data will also be discussed with respect to the results of yet another study employing dive recorders (activity below the water surface) on some of the VHF-equipped birds (Luna and Culik, Mar Ornit, 1997).

Session 11 - 3

MEASUREMENT OF TEMPERATURE
AND POSITION OF AN EGG IN THE
NEST BY TELEMETRIC SYSTEM

Paulo José Abatti, Sérgio Francisco Pichorim & Christian De Marino Fernandes
CPGEI / CEFET-PR - Paraná Federal Center of Technological Education
Av. Sete de Setembro, 3165 CEP : 80230-901 - Curitiba - Paraná - Brazil

INTRODUCTION

This work describes a biotelemetry system for continuous monitoration of temperature and position of an artificial radio transmitter egg in a small bird nest.

METHODS

The egg (dimensions: 38mm x 24mm, weight: 12g) is composed by a modified block oscillator working as a PPM circuit, with transmitting radio frequency of 400kHz. Temperature modulates the relative position of transmitted pulses[1]. Signal reception (through ellipsoidal coils placed externaly around the nest) is done by four antennas in quadrant, two by two combinated, in order to get the signal from any position of the transmitter in the nest. The receptor circuit is responsible to separate and process the informations of temperature and angular position (static and dynamic) of the egg in the nest. The informations are analised and stored by an IBM compatible PC connected to the receptor circuit through the parallel interface. The receptor is composed by an analog circuit that realizes arithmetic operation with the signal from the antennas. In addition, a 6-bit digital circuit (4 bits for the output position signal, 1 bit for the output temperature signal and 1 bit for the multiplex selection proceeding from the computer) is responsible for the logic operation with this signal and interface with the microcomputer. The software, developed in C language, processes, presents graphically and stores the received data for posterior analysis.

RESULTS

The system has been submitted to extensively bench tests showing, for instance, that egg internal temperature can be measured in a 20 to 50°C range, resolution of 0.2°C, with an average error of less than 1%. Power consumption was about 0.12µW per transmitted pulse, and it was able to operate continuously over 1 month, using a miniature silver battery (Eveready n. 379). The egg position inside the nest can be mesured with a resolution of 22.5º, because it is registered with 4 bits, presenting an average error of 1.6%.

DISCUSSION & CONCLUSIONS

Tests in vitro showed the viability of the system in monitoring temperature and position of small bird's egg, and field tests will be done in the beginning of 1997.
[1] - Pichorim, S. F. and Abatti, P. J., "A temperature telemetry system based on a single transistor PPM transmitter with remote switching.", Biotelemetry XIII, 1995.

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Session 11 - 4

RADIOTELEMETRY ON SONG-BIRDS

Thorwald O. Feuerabendt, Gerhard Breutel, Johannes Sagunsky, Manfred Gahr
MPI für Verhaltensphysiologie Seewiesen, Post Starnberg D-82319 Seewiesen,
Phone +49 8157-932382, FAX +49 8157 932 400

INTRODUCTION

We need telemetry for transmission of physiological data. Sex differences as the basis of investigation can help to elucidate phenomenons correlations in neurobiology and ethology. Electrophysiology of behaviour is one element in such endeavour. Canaries (Serinus canaria) song behaviour supplies a suitable objekt of research.Both singing and, nervous system show sex-specifity.

METHODS

To capture a great deal of parameters singing has to be free of artificial exertion of influence. To that purpose we evolve a special recording equipment. A miniature FM transmitter which weighs below 2 g (under construction about 1 g or less) should broadcast spikes out off the vocal control system ( some forebrain areas) of songbirds. When we are doing this, birds are absolutely free of disturbance in mobility and any form of anesthesia or stimulant.

RESULTS

A range of more than 10 metres seems to be possible. There is no disturbance in song behaviour by transmitter-application. Longterm recordings (about 1 month) of high quality are within reach.

Session 12 - 2

THE STUDY OF RAPTOR MIGRATION
USING SATELLITE TELEMETRY:
SOME GOALS, ACHIEVEMENTS AND LIMITATIONS

Bernd-U. Meyburg & Christiane Meyburg
World Working Group on Birds of Prey
Wangenheimstr. 32, D-14193 Berlin, Germany

INTRODUCTION

Many species of birds of prey (Falconiformes) spend over half of the year outside their breeding territory, on migration and in their winter quarters. Whereas their behaviour during the breeding season is often closely studied, our knowledge of the remaining part of the year is very slight. For the past few years satellite telemetry has provided a new aid towards an intimate study of long-distance migrations.

METHODS

During the period July 1992 till October 1996 we have fitted 57 raptors of ten different species , including 15 Steppe Eagles Aquila nipalensis, 14 Lesser Spotted Eagles A. pomarina, 7 Imperial Eagles A. heliaca, 7 Greater Spotted Eagles A. clanga and 7 Ospreys Pandion haliaetus, with satellite transmitters (PTTs) ranging in weight from 30 to 95 grams. 19 of the PTTs used, mainly since 1995, were solar-powered, the others had conventional batteries. After the early phase of the study, when more easily accessible nestlings were equipped, we moved to trap and study adult and immature individuals, which have the advantage of a higher survival rate.

RESULTS

For the first time ever in ornithology it has been possible to track the full year-round migration movements in several species, e.g. in the Lesser Spotted Eagle, Imperial Eagle, Wahlberg’s Eagle and Osprey. The most impressive migration tracked so far was that of an adult male Lesser Spotted Eagle between its breeding grounds in northern Germany and its wintering quarters in Zambia, over a total distance of over 19000 kilometres. Some unknown migration routes have been discovered, such as the intracontinental trans-equatorial migration of the Wahlberg’s Eagle in Africa, the loop migration of the Steppe Eagle around the Red Sea, the crossing of the Osprey over the widest part of the Mediterranean Sea, the to-and-fro east-west migration of the Imperial Eagle between China and Saudi Arabia and the long-distance migration of the Greater Spotted Eagle south beyond the Equator. Through the introduction of solar-powered PTTs it has become possible not only to document the migration routes much more precisely than with PTTs with conventional battery supply, but also to study aspects such as migration speed, daily migration pattern, roosting behaviour etc.

Session 12 - 3

TRACKING OF ADULT MALE AND FEMALE
LOGGERHEAD SEA TURTLES BY
MEANS OF THE SATELLITE
BIOTELEMETRY SYSTEM

Wataru Sakamoto#1, Nobuaki Arai#1 and Norihisa Baba#2
#1: Faculty of Agriculture, Kyoto University
606-01 Kyoto, Japan
#2: National Research Institute of Far Seas Fisheries
5-7-1, Orito, 424 Shimizu, Japan

INTRODUCTION

For the last decade, yearly nesting number of loggerhead turtles in the North Pacific Ocean are gradually decreasing. Adult female sea turtles land on sandy beach to lay eggs. The nesting beach is nearly same where they themselves hatched. The mechanism how turtles detect the same beach is unknown. Furthermore the behavior of adult males are hardly known since they never land throughout their lives. The purpose of this research is to know the migration paths of loggerhead turtles in the North Pacific Ocean using satellite tracking system. And these migration paths will be referred to sea turtle conservation program.

METHOD

Three satellite transmitters (PTTs) were attached to 2 females (F-1, -2) and a male (M-1). Females were released from nesting beach, F-1 was released on July 28, 1995, F-2 was on August 3, 1996. The male was captured by a set net off the nesting beach on January 9, 1996 and released again 10 days after attaching a PTT. The locations were recorded for 4, 4, and 8 months respectively through Argos system. Migration paths were referred to earth's geomagnetic field, the sun orbital along with their paths.

RESULTS

Two female turtles arrived at the same southwestern feeding ground, the East China Sea, soon after the nesting season. However the migration path was different; F-1 migrated southern side of the Kuroshio, while F-2 moved northern side of the Kuroshio along Japan Island. The courses were separated by the prevention from strong against northeastern current. Total migration distance were about 1500 km. The male turtle migrated in southern warm water areas during spring season. Five months later from release, in early summer, it returned to coastal zone neighboring the nesting beach to mate with females. It migrated about 2000 km in total before arriving again at the nesting beach.

DISCUSSION

The sun orbital was suggested the possible method to detect the temporal progress in the ocean. Similar sunrise hour was shown for F-1 in the periods of its returning to the East China Sea. The similar sunset hour was shown for the male turtle when it began to return to the nesting beach. We think the earth's geomagnetic compass is not so available for the turtles to know the seasonal or temporal transition in the ocean.

Session 12 - 4

ARGOS SYSTEM EVOLUTION FOR ANIMAL TRACKING

M. Taillade
Collecte Localisation, Satellites 18 avenue E. Belin 31055 Toulouse, France.

The Argos Data Collection and Location Satellite System is operated under a partnership agreement between NOAA (National Oceanographic and Atmospheric Administration - U.S.A.) and CNES (Centre National d'Etudes Spatiales - France) to provide a worldwide in-situ environmental data collection and Doppler-derived location service.

One of the most significant use of Argos involves the location and collection of data associated with scientific programs that study animals (birds , marine and terrestrial animals) all over the world.

During late 1994, an independent survey of the major international users was conducted to obtain their perspective on Argos system capabilities.

Further clarification of Argos system User requirements was obtained through responses to an extensive Argos questionnaire that was distributed in mid-1995.

The results of the survey indicated that certain Argos system Users' requirements could only be addressed through modification of the satellite instrument along with associated changes in ground system management.

The User requirements are summarized as follows:
- Improve Satellite Coverage
- Increase Data Volume transmission capability
- Improve Satellite Receiver Sensitivity to reduce platform size and power requirements or enhance transmission performance
- Allow to control platforms remotely by having a two-way communication capability with the satellite

The desirability of many of these improvements was anticipated by Argos, and this paper will present plans for the second generation (Argos-2) beginning in 1997.
Enhancements for the third Argos generation (Argos 3) beginning in 2001 are under discussion and are presented.
Keywords: Argos, Satellite, Animal, tracking, location, data collection

Session 12 - 5

HABITAT USE ANALYSIS USING THIESSEN POLYGON AND TRIANGULATED IRREGULAR NETWORK INTERPOLATION

Jim Casaer, Martin Hermy & Pol Coppin
Labortory for Forest, Nature and Landscape Research / K.U.Leuven
Vital Decosterstraat 102
B-3000 Leuven / Belgium

BACKGROUND

Since Burt defined "home range" in 1949, a range of methods have been proposed to quantitatively appraise it, but the literature shows that no consensus has been reached. And even the concept of "home range" itself has been questioned now. Nevertheless, habitat use analysis requires some form of numeric assessment to facilitate a scientific evaluation of the interaction between animals and their environment. This paper proposes a new non-parametric model to estimate habitat use using Geographical Information Systems (GIS) technology.

MODEL DESCRIPTION

Contrary to many other home range models, e.g. the Ellipse and Minimum Convex Polygon models, the proposed model is based on "internal" home range use. In order to evaluate this concept, the utilisation distribution or UD must be derived from the distribution of the observation locations themselves and can not take into account a priori assumptions concerning the nature of the UD distribution, nor are ancillary parameters derived as is the case with more sophisticated parametric models .

Thiessen polygon interpolation around the collected location points divides the continuous feature space into discrete units. The model subsequently assigns to each location point the inverse values of the respective Thiessen polygons. These values are a quantitative indicator of intensity of habitat use (number of observations per area unit), and serve as input to an triangulated irregular network or TIN interpolation surface. The resulting three-dimensional model effectively depicts habitat use, whereby the area representing 95% of the total volume of this 3-D model is defined as the home range.

The ability of the proposed model to accurately derive habitat use was tested using a dedicated software package to simulate home range use in consecutive iterations with different numbers of observations. Grid analysis (Arc/Info operator) and Kappa coefficients of agreement served as evaluation tools.

CONCLUSIONS

Accuracy assessment with both the grid analysis procedure and Kappa coefficient computations revealed a high degree of correspondence between model and simulation. The fact that model construction was done in the Arc/Info GIS environment allows for easy integration with habitat feature collection. It must be stated, that the model facilitates in essence an appraisal of habitat use, which is not synonymous with home range definition.