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At least 127 records · Page 7Linked to original sources

PubMed1998

The forces in the distal femur and the knee during walking and other activities measured by telemetry.

The forces and moments in the shaft of a distal femoral replacement were measured by telemetry for a subject during different activities, and calculations were then made of the forces at the knee. The axial force showed a small peak at heel-strike followed by two main peaks during stance. In level walking, the peak axial force was between 1,487 and 1,718 N (2.2-2.5 BW), the peak shear force was 269-368 N (0.4-0.54 BW) directed anteriorly on the tibia, the peak axial torque was 7 Nm internal, while the patellofemoral force was 466-571 N. The highest axial force was recorded for descending stairs (2.8 BW). Standing on one leg produced 2.4 BW, while lying supine and raising the leg produced 1.7 BW. The data produced may resemble that of a normal subject, and has application to basic joint mechanics, to joint reconstruction, and to total knee replacement design and evaluation.

Adult↗

PubMed1997

Implantation of a refillable glucose monitoring-telemetry device.

This study describes the components and short-term in vivo evaluation of an integrated implantable system consisting of an amperometric glucose biosensor, a miniature potentiostat, a FM signal transmitter, and a power supply. The device (dimensions: 5.0 x 7.0 x 1.5 cm) was implanted subcutaneously in healthy mongrel dogs. The biosensor performance was evaluated in vitro prior to implantation using standard solutions simulating the physiological environment. A linear response to glucose concentration was observed throughout the physiological and pathophysiological range (with an upper limit of 25 mM glucose, and a sensitivity of 0.5 microA/mM). The results of short-term subcutaneous implantation of the integrated system demonstrated good agreement between the glucose concentration measured by the biosensor and that obtained using standard glucose determination methods. The delay-time between the tissue glucose level (measured by the biosensor) and the blood glucose level (obtained by standard methodology) was 3-7 min. These results demonstrated the feasibility of data transmission by a telemetry system through the skin of a dog and allowed the commencement of chronic in vivo testing. During the chronic implantation the biosensor was refilled in vivo. A rejuvenation of the sensor's response after refilling was observed suggesting the potential of such sensors for long-term implantation.

Animals↗

PubMed1996

Short-term canine implantation of a glucose monitoring-telemetry device.

In this study we report the development and short-term in vivo evaluation of an integrated implantable device consisting of an amperometric glucose biosensor, a miniature potentiostat, a FM signal transmitter, and power supply. The device (dimensions: 5.0 x 7.0 x 1.5 cm) was implanted under the skin of medium-size anaesthetized dog. The experimental set-up included several methods for data collection: analog recording via wired X-T chart recorders; data collection by wearable microprocessor--data logger, and remote data collection via antenna and receiver linked to a computer-based data acquisition system. The device (sensor) performance was evaluated in vitro prior to implantation, using different model solutions simulating the physiological environment. A linear response to glucose concentration was obtained up to 25 mM glucose, with a sensitivity of 0.5 microA/mM. The results of short-term subcutaneous implantation of the integrated device reveal adequate monitoring of an artificially-induced glycaemia. The delay-time was 3-7 minutes. These tests demonstrate the feasibility of data transmission by the telemetry system through the skin of a medium-sized dog and allow the commencement of chronic in vivo experimentation.

Animals↗

PubMed1997

The Cosmed K4 telemetry system as an accurate device for oxygen uptake measurements during exercise.

The purpose of this study was to test the accuracy of oxygen uptake (VO2) measurements using the Cosmed K4 portable telemetry system. This system of higher technology than the original Cosmed K2 device, contains a CO2 electrode allowing measurements alternatively by either the Cosmed K4 system (K4) or the CPX Medical Graphics (CPX) during a maximum oxygen uptake (VO2max) ergocycle test, at rest and during several submaximal exercises (25, 50 and 75% of maximal work rate) in seven subjects. Heart rate values were comparable for exercise at the same work stage during gas collection using the two systems, indicating that the physiological stresses were similar. The VO2 values did not significantly differ at rest (4.40+/-0.83 vs 4.16+/-0.58ml x min(-1) x kg[-1]), at 25% Wmax (20.97+/-1.31 vs 21.32+/-2.54 ml x min(-1) x kg[-1]), at 50% Wmax (33.32+/-3.92 vs 33.50+/-3.51 ml x min(-1) x kg[-1]), at 75% Wmax (47.01+/-7.51 vs 47.49+/-7.11 ml x min(-1) kg[-1]) and at maximal intensities (62.07+/-8.48 vs 62.84+/-11.31 ml x min(-1) kg[-1]) using K4 and CPX devices, respectively. The results of this study indicated that the K4 system was accurate for all oxygen uptake measurements from rest to maximum exercise levels.

Adult↗

PubMed1975

An intra-oral telemetry system for the continuous recording of vertical jaw movement.

Continuous measurement of the separation between upper and lower dental arches, the so-called interocclusal distance (10D), is of interest in dentistry. Criteria for making such measurements by radio telemetry are discussed. It is concluded that a transmitter small enough to fit in a molar tooth gap is necessary in order to minimize interference with normal function; other design factors are related to obtaining adequate frequency stability, on which measurement accuracy depends. A transmitter fulfilling these requirements is described which sensed the instantaneous value of 10D by the frequency change produced when a metallic object (dental filling, gold crown, shorted turn of wire or piece of ferrite) in one dental arch moved relative to the transmitter in the other. Errors due to lateral and protrusive jaw movements were measured. Careful design and the use of high grade ceramic chip capacitors resulted in a transmitter of good frequency stability (+/- 0.03% in 10 h, +/- 0.02%/degrees c) and small size (10 X 7 X 5 mm). An example is given illustrating 10D movements due to swallowing, speech and respiration.

Humans↗

PubMed1995

[Preliminary study of an implantable device powered by an inductive link for telemetry of the epicardial electrocardiogram and the radionuclide activity of the left ventricle].

In nuclear cardiology, radionuclide data concerning the cardiac function are presently collected using external detectors, providing scintigraphic images or activity curves with respect to time. This paper presents a new approach to the latter kind of instruments, which are often called nuclear stethoscopes. This proposed system is composed of a cardiac implant, a miniature transmitter positioned externally on the chest and a remote receiver system allowing the processing of the cardiac function data. The transcutaneous magnetic link permits the power transfer in order to energize the electronic implant, and permits the telemetry of the electrocardiogram and the radionuclide data between the implant and the external receiver system. The nuclear activity measured by a photodiode for gamma rays based on cadmium telluride, with pulse width modulation, constitutes the carrier of the electrocardiographic activity. The composite signal is transmitted by means of the implant impedance modulation. The use of this transmission concept reduces to a minimum the volume of the implant. Furthermore, this system, allowing the correct positioning of the external transmitter facing the left ventricle, increases the performance of the global transmission system. Theoretical results on the design of the magnetic link are presented.

Electrocardiography↗

PubMed1985

Polysomnographic telemetry using Telediagnostic and Oxford Medilog 9000 systems.

Sleep was recorded in 24 normal adult sleepers (21-42 years of age) for 4 consecutive nights (2 nights in the laboratory and 2 nights in the home environment) using one of two commercially available telemetry systems, either the Telediagnostic or the Oxford Medilog 9000. Modifications to each system were necessary to approximate standard laboratory techniques for polysomnography. With comparability in recording techniques between systems, there were no qualitative or quantitative differences in standard electroencephalogram sleep parameters recorded in either the home or laboratory environment.

Adult↗

PubMed1977

Urine marking and territoriality in Galago alleni (Waterhouse, 1837--Lorisoidea, Primates)--a field study by radio-telemetry.

A wild population of Galago alleni was controlled by trapping and followed by radio-tracking in the equatorial rainforest of Gaboon during three study periods of 3 months each in 1972, 73 and 75. The disposition of territories and the social organization are described, as well as their evolution through time. A new technique of radio telemetry permitted identification and localization of urine marking in wild galagos. Urine marking took place throughout the territory, with a fourfold increase in frequency in zones where there is a slight overlap with neighbouring territories (female--female or male--male). The function of urine washing (wetting of the soles of the feet with urine) is discussed in relation to five hypotheses proposed by different authors, and th data obtained in the field in Gaboon. We interpret this behaviour as a means of dispersal of urine marks (social signals) in a three-dimensional milieu where displacement by a combination of leaping and running creates numerous pathways.

Animals↗

PubMed1975

Electrical activity of grafted myometrium and its recording by radio-telemetry in unrestrained rabbits.

1. The electrical activity in myometrial grafts in fifty-one female rabbits with ear chambers fitted with pick-up electrodes has been monitored. An FM telemetry system has made long-term studies possible in the freely moving animal. 2. Two distinct patterns of electrical activity were observed either arising spontaneously or provoked by oxytocin. These were the 'long-duration burst' containing about 50-150 spikes, and the 'short-duration burst' containing 1-10 spikes. 3. The spike frequency within the long-duration bursts varied between 0-9 and 1-3 spikes sec-1 and was fairly constant during the first half of the burst. The frequency of the bursts in the long series of short-duration bursts was about 2-3 min-1. 4. When activity from grafts in two chambers in the same animal was monitored for long periods, spontaneous activity occurred at random throughout the day in each graft, indicating that the spontaneous activity was probably myogenic.

Animals↗

PubMed1985

An optical telemetry device to identify which dolphin produces a sound.

A small telemetry device, called a "vocalight," was designed for attachment to a dolphin's head using a suction cup. The vocalight lights up a variable number of light-emitting diodes depending upon the loudness of sounds received at a hydrophone within the suction cup. If vocalights matched for sensitivity are put on each dolphin within a captive group, observers can identify which dolphin produces a vocalization. Use of vocalights indicates that source levels of whistles from captive bottlenosed dolphins, Tursiops truncatus, range from approximately 125 to over 140 dB re: 1 microPa at 1 m.

Animals↗

PubMed1999

Presurgical evaluation of patients with epilepsy and normal MRI: role of scalp video-EEG telemetry.

When considering surgery for intractable partial seizures, even with high resolution MRI, some patients do not show structural abnormalities. The aim was to consider whether these patients were likely to proceed to surgical treatment after scalp video-EEG telemetry. All patients undergoing presurgical evaluation at the National Hospital for Neurology and Neurosurgery between 1995 and 1997 were reviewed and 40 were identified without definite MRI abnormalities. None of 40 disclosed a well localised epileptogenic zone concordant with other tests that would have allowed the patient to proceed directly to surgery. In five of the 40, evaluation led to a hypothesis that could be tested by intracranial studies; three proceeded to surgery. It is suggested that high quality MRI is performed first when surgical evaluation is undertaken and if negative the patient carefully counselled before proceeding with any investigations, as successful resective surgery is an unlikely outcome in such MRI negative cases.

Adolescent↗

PubMed1979

A multichannel telemetry system for recording cardiovascular neural signals.

A multichannel telemetry system was developed for use with chronically instrumented unrestrained cats. This system can simultaneously record efferent and afferent cardiovascular neural signals, bioelectrical noise arising near the electrode recording the neural signals, EEG, ECG, and a standard calibration signal. The miniature (18 cm3), lightweight (24 g), telemeter is a five-channel, time-multiplexed, pulse width modulation (PWM)/FM device employing a high frequency subcarrier (60 kHz) and two sampling frequencies (30 kHz and 6 kHz). The device is powered by two small 120 mA . h silver oxide cells; it has an indoor transmission range of 10 m and can operate for 48 h. One channel transmits a standard signal (a square wave of 100 Hz and 200 mVp-p) used to monitor and regulate the system's performance. When the variation in either the amplitude or frequency of the standard signal is greater than 10% of the control value, the transmitted bioelectrical signals are automatically discarded.

Animals↗

PubMed1980

Elimination of noise in telemetry systems by pulse-width discriminator.

A pulse-width-discriminator circuit (PWD) was developed and applied for noise reduction in an FM pulse-interval-ratio modulation telemetry system. The PWD was incorporated as an intermediary between the tuner and the demodulator. The application of the circuit as a noise filter is a result of its ability to distinguish between pulses of different durations and its ability to eliminate pulses whose durations are less than some predetermined value. Since spikes of radio-frequency interference (RFI) occurring at the tuner output were of significantly shorter duration than the encoding pulses, they were virtually eliminated by the PWD. This prevented false triggering of the demodulator and resulted in a noise-free final demodulated output signal. This system was tested during telemetered blood pressure measurements in an unrestrained dog and proved to be extremely effective in eliminating spurious noise caused by electromagnetic interference in the radio-frequency range.

Blood Pressure Determination↗

PubMed1980

An inexpensive pressure telemetry system.

An inexpensive telemetry system using transducers and recorders commonly available, i.e., Statham and Grass, is described. The direct-current signal of a Statham transducer is applied to a voltage-controlled oscillator, thereby frequency encoding the pressure sensed by the transducer. This encoded signal frequency modulates a Colpitts oscillator, which acts as a radio-frequency oscillator-transmitter in the 88- to 108-MHz band. This transmitter and transducer, along with a rechargeable NiCd battery pack (total wt 0.5 kg), are mounted in a canvas jacket and worn by a dog previously prepared with a chronic indwelling arterial catheter. With a fully charged battery pack, a signal can be transmitted up to 250 ft for 50 h. A frequency-modulation automotive receiver, powered by and interfaced with a Grass 7B recorder, receives the signal and drives a tachometer circuit that reconverts the audio-frequency signal to a voltage proportional to pressure. This voltage is then applied to the driver amplifier of the Grass to produce a charted record. This system introduces no distortion as seen by comparison of direct and telemetered signals and is drift free for intervals exceeding 24 h.

Animals↗

PubMed1983

Crystal-controlled telemetry system for long-term acquisition of physiological data.

A crystal-controlled telemetry system was developed for long-term high-reliability recording of blood pressure in unrestrained animals. The miniaturized transducer-transmitter system is powered by two lithium batteries that allow for more than 200 h of continuous recording of blood pressure before battery replacement. The total system has a flat frequency response of 0-25 Hz and a time stability of +/- 1 mmHg/day. Linearity is better than 0.5%. The high degree of dependability of the system permits us to perform continuous, unattended, around-the-clock recordings of pressure and heart rate in unrestrained animals. Very high dependability is achieved by the use of a novel piezoresistive blood pressure transducer and by the inherent stability of the crystal-controlled radio-frequency oscillator of the transmitter. The receiver is also crystal tuned to the measured transmitter frequency. This transmitter-receiver frequency locking ensures very reliable reception of the telemetered signal.

Animals↗

PubMed1975

A multichannel implantable telemetry system for flow, pressure, and ECG measurements.

The design of telemetry systems for chronic implantation within the body have progressed from simple single-channel devices to complex multichannel systems over the last 15 yr. Although chronic measurements of temperature, ECG, and pressure have been reported with good results, measurements such as dimension and blood flow have been difficult because of heavy power requirements. The design to be described is a multiplex system that will measure up to eight individual parameters simultaneously, including blood flow. Flow is measured using an electromagnetic transducer, and by special design, the normal high power requirements of the electromagnetic technique have been reduced to a few hundred milliwatts. The system is powered by two NiCad, rechargeable batteries which are periodically recharged through the intact skin by induction at 250 kHz to an implanted pickup coil. The presently constructed units have been configured to measure ECG, two pressures, temperature and ascending aortic flow.

Animals↗

PubMed1986

Miniaturized eight-channel telemetry system for long-term EEG registration of humans and laboratory animals.

According to the increasing importance of telemetric EEG registration, a miniaturized telemetry system for AC and DC transmission has been developed. The basic model has been constructed for the demands of experiments with small rodents. The transmitter is 19 X 13 X 5 mm in size and weighs 5 g including two 1.5 V batteries. The transmission of AC or DC potentials can be chosen for each channel separately. In the case of eight-channel transmission, the bandwidth ranges from 0.8 to 100 Hz, and in the case of using only one channel, signals up to a frequency of 17 kHz may be registered. Semimicroelectrodes with an electrode impedance of about 10 M omega, as well as conventional surface electrodes can be applied. In case of long-term EEG registration of humans the total amplification at V = 1,000 has to be enlarged by using an extension module. This module consists of an additional amplification stage, a modified HF oscillator to enlarge the omnidirectional transmission sphere and external batteries to increase the operation time of the transmitter. Small dimensions, light weight and multifunctionality plead for the attractivity of this construction according to various clinical and experimental demands.

Animals↗

PubMed1985

Monitoring heart and breath sounds by telemetry.

A system for FM radiotelemetry of heart and breath sounds is described. Patients' heart and breath sounds are detected by oesophageal or precordial stethoscopes. The anaesthetist, carrying a portable radio receiver, is then free to move around theatre while listening to these sounds through headphones or an ear-piece. The FM telemetry system has also been used to assist patient monitoring in noisy environments such as ambulances.

Anesthesiology↗