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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↗
PubMed2005

Continuous monitoring of circadian variations in intraocular pressure by telemetry system throughout a 12-week treatment with timolol maleate in rabbits.

AIM: The aim of this study was to examine the effect of a 12-week treatment with two formulations of timolol maleate on the amplitude of the circadian fluctuation in intraocular pressure (IOP). METHODS: Conscious Japanese White rabbits housed under a controlled 12-hour light-dark cycle were used. IOP was measured by a telemetry system. Each animal was treated topically for 12 weeks with 0.5% timolol solution (TM) twice-daily, 0.5% timolol gel-forming solution (TM-gel) once-daily, or saline twice-daily, and the circadian variation in IOP was measured every week. RESULTS: Administration of TM or TM-gel did not change IOP in the light phase, but significantly reduced it in the dark phase in each of the 12 weeks. The IOP reductions at 2 h after administration in the TM and TM-gel groups over the 12 weeks were, respectively, 3.6 +/- 0.3 mmHg and 3.4 +/- 0.2 mmHg versus the Saline group. The amplitudes of the circadian fluctuations in IOP in the TM group in weeks 3, 6, and 12 were 15%, 15%, and 18% smaller than those in the Saline group, while the corresponding values for the TM-gel group were 18%, 16%, and 19%, respectively. CONCLUSIONS: TM-gel administered once-daily was as effective at lowering IOP as TM administrated twice-daily over the 12-week experimental period. This study reveals that, in rabbits, both formulations of the timolol maleate induced significant IOP reductions in the dark phase and decreased the amplitudes of the circadian fluctuations in IOP for 12 successive weeks.

Adrenergic beta-Antagonists↗
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↗
PubMed2001

Estimation of psychophysical levels using the electrically evoked compound action potential measured with the neural response telemetry capabilities of Cochlear Corporation's CI24M device.

OBJECTIVE: The goal of this study was to estimate psychophysical levels using the electrically evoked compound action potential (EAP), measured with the Neural Response Telemetry capabilities of Cochlear Corporation's Nucleus CI24M cochlear implant system. DESIGN: Twelve postlingually deafened adults with at least 3 mo of implant experience with the CI24M were subjects in this study. EAP growth functions were successfully quantified on each active electrode of every subject. Correlation and regression analyses were performed between EAP measures and cochlear implant fitting psychophysics. Other information including performance, etiology and duration of hearing loss, and individual electrode impedance was considered. RESULTS: EAP thresholds were found to be highly correlated with psychophysical thresholds. The rate of EAP growth with increasing stimulation levels was also found to be correlated with the dynamic range of loudness limits and psychophysical thresholds in some subjects. No relationship was evident between EAP measures and speech perception tests. CONCLUSIONS: Information from EAP growth function measurements may be used to estimate psychophysical information used in cochlear implant fitting but not to predict performance with the device.

Adult↗
PubMed2002

Speech perception using maps based on neural response telemetry measures.

OBJECTIVE: To determine how speech perception is affected for Nucleus cochlear implant users when their speech processor is programmed using neural response telemetry (NRT) measures rather than traditional behavioral estimates of threshold and maximum comfort level. DESIGN: Electrically evoked compound action potential (EAP) thresholds were measured for a group of 10 adult Nucleus cochlear implant users. These physiologic threshold estimates were used to create three SPEAK MAPs. One MAP ("+10/-20 MAP") was created using only the NRT data. The second MAP ("Combined MAP") was created using a combination of both EAP thresholds and a single behavioralmeasure of threshold and maximum comfort level from electrode 10. A third MAP ("Measured MAP") was created using standard programming techniques. Speech perception was then assessed using each of these three MAPs for either CUNY or HINT sentences presented at two different presentation levels (70 dB SPL and 55 dB SPL). RESULTS: On average, at the higher presentation level (70 dB SPL) subjects performed significantly better when using the Measured MAP than whenusing either of the NRT-based MAPs. No significant difference in speech perception was obtained for either of the three MAPs when the lower presentation level (55 dB SPL) was used. CONCLUSION: This study demonstrated that at relatively high presentation levels, speech perception scores obtained by subjects who use MAPs based solely or primarily on EAP thresholds ar eslightly lower than similar scores obtained using a more traditional MAP. This difference did not reach statistical significance at lower presentation levels. We interpret these findings in a positive light to suggest that although NRT-based MAPs may not be optimal, they are of sufficient quality to support reasonable levels of speech understanding. This is important to establish because these MAPs may prove to be most useful when very young children receive a cochlear implant.

Brain↗
PubMed2005

A different approach to using neural response telemetry for automated cochlear implant processor programming.

OBJECTIVE: This study explores the theoretical relation between the psychophysically measured current levels required for sound processor fitting in cochlear implants and the objectively measured compound action potential threshold (as measured by Neural Response Telemetry, NRT). The objective was to gain understanding of the variability across implantees in this relation and determine possible ways (using objective measures) of improving the predictability of NRT thresholds for behavioral levels needed for mapping. DESIGN: A model of how rate of stimulation affects loudness is presented. The model can be used to understand differences among implantees in the way that rate affects loudness and hence explain the disappointing correlation between NRT and psychophysical measures. Suggestions are made, based on the model, for additional information that may improve the usefulness of NRT measurements. One such option (measuring the effect of interphase gap on NRT amplitude) was experimentally explored in eight subjects (26 electrodes). It was hypothesized that the current change required to maintain equal NRT amplitude when interphase gap was changed from 8 to 45 musec would be correlated with the offset between behavioral and NRT thresholds. RESULTS: The above hypothesis was not supported by the data, and several possible reasons for this outcome are discussed. CONCLUSIONS: The loudness model provides useful insights into why NRT thresholds are not good predictors of the behavioral levels needed for mapping and how NRT might be made more useful by additional objective information. These insights should be investigated in further experimental studies.

Action Potentials↗
PubMed2000

EEG telemetry with closely spaced electrodes in frontal lobe epilepsy.

The use of additional electrodes (other than standard 10-20 electrodes) has proved to be extremely useful in the investigation of patients with temporal lobe epilepsy. The development of 32- and 64-channel EEG machines, along with the reformatting capabilities of digital EEG has greatly increased the possibilities in the number of electrodes and recording montages. The authors wanted to determine whether the use of closely spaced electrodes designed to increase the coverage of frontocentral regions is of benefit in the investigation of patients with frontocentral epilepsy. Patients investigated for frontocentral epilepsy underwent EEG telemetry with closely spaced electrodes based on the 10-10 nomenclature. Twenty-three patients were studied. An additional 30 minutes was required by technicians to create the montage. Unilateral frontal or frontocentral epileptic abnormalities were observed in 10 patients, independent bifrontal in 5 patients, synchronous bifrontal in 4 patients, and no EEG changes in 4 patients. In no patient did the addition of closely spaced electrodes lead to a change in the classification of the EEG. Closely spaced electrodes did not reveal focal abnormalities, which were not already apparent with 10-20 electrodes, nor did they demonstrate evidence of laterality in bilaterally synchronous discharges.

Electrodes↗
PubMed2001

Teaching telemetry.

For patients on telemetry monitoring, knowledge is power--and comfort. You can develop informative tools to help critical care nurses put these patients at ease.

Adult↗
PubMed2006

Intrauterine growth restriction increases blood pressure and central pulse pressure measured with telemetry in aging rats.

OBJECTIVES: Intrauterine growth restriction (IUGR) is associated with a higher risk of hypertension in adulthood. In Western countries, IUGR is based on uteroplacental dysfunction. We hypothesize that aging augments the increased baseline blood pressure after IUGR and alters the cardiovascular response to acute stress. METHODS: To evaluate blood pressure during aging in the rat, we used a model of uteroplacental dysfunction (bilateral uterine artery ligation). Blood pressure was measured in male offspring at the ages of 6, 9, and 12 months using telemetry, allowing for unstressed measurements in conscious animals. At 6 and 12 months of age, cardiovascular data were obtained during acute olfactory stress induced by ammonia and subsequent recovery. RESULTS: Rats born after IUGR had lower birth weights (4.6 versus 6.5 g, P < 0.001) and did not completely catch up in weight by 12 months of age (519 versus 567 g, P < 0.01). Systolic blood pressure was significantly higher in IUGR animals at all ages. Pulse pressure (PP) was identical in both groups at the age of 6 months. However, PP increased in the IUGR group with increasing age, unlike the control group, and was significantly higher at 9 and 12 months of age. At the age of 12 months, there was a highly significant negative correlation between birth weight and PP (r = -0.82, P < 0.001). IUGR rats reached a higher peak in systolic blood pressure during stress, and showed a longer period for the raised heart rate to recover after stress. CONCLUSIONS: IUGR is associated with raised baseline blood pressure, an increasing PP with age, and an altered stress response.

Aging↗
PubMed2006

Ambulatory EEG telemetry: how good is it?

When someone asks the question, how good is ambulatory EEG telemetry, there is no correct answer. There are many manufacturers of ambulatory EEG technology. Each device has its own strengths and weaknesses. What one is really interested in when one asks such a question needs to be defined in terms of expectations and technical capabilities for the piece of equipment under discussion. Systems exist or can be easily modified to be as sophisticated as the best of the inpatient units. However, is that level of sophistication needed for the ambulatory based recordings? Again, the answer to that is dependent on the ordering physician's expectations. Below is a discussion of the different clinical expectations that are frequently encountered and the needed requirements for an ambulatory system to properly address them.

Diagnosis, Computer-Assisted↗
PubMed2000

A telemetry system for the study of spontaneous cardiac arrhythmias.

The characteristics of spontaneous cardiac arrhythmias leading to sudden cardiac death are largely unknown. To study arrhythmias in animal models, an eight-channel implantable radio telemetry system has been developed to record continuously cardiac electrograms over a period of weeks to months, with maintenance restricted to changing batteries. The inputs are connected in a unipolar manner. Each channel has a gain of fifty and is AC coupled, band limited to 0.07-260 Hz. The signals are digitized with 12 bits resolution at 1000 samples/s. The amplifiers, analog-to-digital converter, and control logic are packaged in an implantable unit. An umbilical cable is passed through the skin to an external backpack unit for power and data transmission. A custom serial interface card, a PC/104 form factor 25-MHz 80386-based single-board computer with a PCMCIA wireless local area network (WLAN) card, and battery power supply make up the backpack. Data are read into the parallel port of the computer, buffered, then transmitted over the WLAN to the laboratory network where it can be analyzed and archived. Approximately 12 h of 14,000 bytes/s data can be collected with each set of batteries. The system is suitable for continuous monitoring of animal models of spontaneous arrhythmias and sudden cardiac death.

Animals↗
PubMed1997

Microcontroller-based underwater acoustic ECG telemetry system.

This paper presents a microcontroller-based underwater acoustic telemetry system for digital transmission of the electrocardiogram (ECG). The system is designed for the real time, through-water transmission of data representing any parameter, and it was used initially for transmitting in multiplexed format the heart rate, breathing rate and depth of a diver using self-contained underwater breathing apparatus (SCUBA). Here, it is used to monitor cardiovascular reflexes during diving and swimming. The programmable capability of the system provides an effective solution to the problem of transmitting data in the presence of multipath interference. An important feature of the paper is a comparative performance analysis of two encoding methods, Pulse Code Modulation (PCM) and Pulse Position Modulation (PPM).

Acoustics↗
PubMed2005

Design and initial evaluation of an implantable sonomicrometer and CW Doppler flowmeter for simultaneous recordings with a multichannel telemetry system.

We have developed a sonomicrometer and continuous wavelength (CW) Doppler flowmeter for a multichannel telemetry system. These developments will enable us to measure ventricular dimension and coronary artery blood velocity, which are valuable parameters to characterize sudden cardiac death (SCD) in ambulatory animal models of ventricular arrhythmias. The design goals for the sensors were accuracy, low power consumption, small size and compatibility with each other. The circuits were designed successfully and tested simultaneously in vivo. The CW Doppler flowmeter draws 9 mA and the sonomicrometer draws 28 mA on a 5-V supply. The ability to measure heart dimension and blood velocity will add significantly to our understanding of the sequence of events leading up to spontaneous sudden cardiac death.

Animals↗
PubMed2005

Micropower circuits for bidirectional wireless telemetry in neural recording applications.

State-of-the art neural recording systems require electronics allowing for transcutaneous, bidirectional data transfer. As these circuits will be implanted near the brain, they must be small and low power. We have developed micropower integrated circuits for recovering clock and data signals over a transcutaneous power link. The data recovery circuit produces a digital data signal from an ac power waveform that has been amplitude modulated. We have also developed an FM transmitter with the lowest power dissipation reported for biosignal telemetry. The FM transmitter consists of a low-noise biopotential amplifier and a voltage controlled oscillator used to transmit amplified neural signals at a frequency near 433 MHz. All circuits were fabricated in a standard 0.5-microm CMOS VLSI process. The resulting chip is powered through a wireless inductive link. The power consumption of the clock and data recovery circuits is measured to be 129 microW; the power consumption of the transmitter is measured to be 465 microW when using an external surface mount inductor. Using a parasitic antenna less than 2 mm long, a received power level was measured to be -59.73 dBm at a distance of one meter.

Action Potentials↗
PubMed2005

Smoking cessation a byproduct of EEG telemetry monitoring.

Smoking is a common problem in epilepsy patients. The inpatient video-EEG monitoring (VEEG) unit provides a unique and conducive environment for epilepsy patients to participate actively in a smoking-cessation program. The restrictions and confinement to the telemetry bed impose a forced abstinence from smoking. It has been suggested that patients who are hospitalized may be more receptive to smoking-cessation advice. We report two patients who were successfully able to quit smoking after admission for VEEG.

Administration, Cutaneous↗
PubMed2006

Stomach temperature telemetry reveals temporal patterns of foraging success in a free-ranging marine mammal.

1. We studied feeding frequency in free-ranging grey seals using stomach temperature telemetry to test if previously reported sex differences in the diving, movement and diet were reflected in the temporal pattern of foraging success. 2. Data were retrieved from 21 of 32 grey seals from 1999 to 2001, totalling 343 days and 555 feeding events, with individual record length varying from 2 to 40 days (mean: 16.33 +/- 2.67 days/seal). 3. Seals fed on 57.8 +/- 6.46% of days sampled and had an average of 1.7 +/- 0.26 meals per day, but individual variability was apparent in the temporal distribution of feeding as evidenced by high coefficients of variation (coefficient of variation = 69.0%). 4. Bout analysis of non-feeding intervals of six grey seals suggests that feeding intervals of individuals were varied and probably reflect differences in prey availability. Grey seals tended to have many single feeding events with long periods separating each event, as would be expected for a large carnivore with a batch-reactor digestive system. 5. We found significant sex differences in the temporal distribution of feeding. The number of feeding events per day was greater in males (2.2 +/- 0.4 vs. 1.0 +/- 0.2), as was time associated with feeding per day (56.6 +/- 5.8 min vs. 43.9 +/- 9.4 min). 6. The number of feeding events varied with time of day with the least number occurring during dawn. Feeding event size differed significantly by time of day, with greater meal sizes during the dawn and the smallest meals during the night. 7. The length of time between meals increased with the size of the previous meal, and was significantly less in males (541.4 +/- 63.5 min) than in females (1092.6 +/- 169.9 min). 8. These results provide new insight into the basis of sex differences in diving and diet in this large size-dimorphic marine predator.

Animals↗
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↗