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PubMed1999

Radiotelemetry system for apnea study in lambs.

Neonatal apneas are being studied in the laboratory using polysomnographic recordings in lambs. Standard equipment, requiring animal restraint, disrupts sleep and prevents development of spontaneous apneas. The aim of the current work was to develop and validate a wireless recording equipment to study freely moving lambs. Firstly, a radiotelemetry equipment composed of a multichannel FM transmitter and a receiver was developed. Secondly, to test the telemetry equipment, each biopotential - [electroencephalogram (EEG), electrooculogram (EOG), electrocardiogram (ECG), electromyograms (EMGs), nasal airflow] - was recorded simultaneously by standard equipment and by telemetry (5 lambs). The results indicated an excellent concordance between signals obtained by both systems. Finally, the 8-channel telemetry prototype was tested for polysomnographic recordings (16 lambs). Results obtained confirmed the possibility of recording frequent REM sleep periods and spontaneous apneas. In conclusion, this radiotelemetry polysomnographic equipment brings new possibilities for research on neonatal apneas.

Animals↗

PubMed2001

Relationship between NRT measurements and behavioral levels in children with the Nucleus 24 cochlear implant may change over time: preliminary report.

OBJECTIVE: Response from spiral ganglion cells to electrical stimulation via the Nucleus 24 cochlear implant can be measured using the neural response telemetry system. The purpose of this study was to assess, in children, the correlation between the neural response threshold and the behavioral levels used for cochlear implant programming process. METHODS: The neural response telemetry test was administered to 23 children (mean age at implantation: 4 years) with the Nucleus 24 cochlear implant. Four intra-cochlear electrodes (electrodes 5, 10, 15 and 20) were tested. The neural response threshold at 3, 6, 9 and 12 months post-implantation was compared with the behavioral threshold and the maximum comfort level estimated during the same periods: a Pearson's correlation test was performed for each tested electrode. RESULTS: On apical electrodes, the correlation with the behavioral threshold remained significant from 3 to 12 months post-implantation (r ranging from 0.696 to 0.909, P<0.05), and the correlation with the maximum comfort level was also significant throughout the study period, except on electrode 15 at 9 months (tendency to significance). On basal and intermediate electrodes, statistical correlations were found only at some points of time; nonetheless, at 12 months post-implantation, a significant correlation with behavioral levels could be clearly demonstrated both on electrode 15 (r=0.914--0.778, P<0.05) and on electrode 10 (r=0.845--0.720, P<0.05). CONCLUSIONS: This preliminary study suggests that the correlation between the neural response threshold and behavioral levels may improve from the base towards the apex of the cochlea. However, a significant correlation can be demonstrated for all tested electrodes at 12 months post-implantation. During the first months post-implantation care must be exercised when interpreting neural response telemetry measurements: a positive test does not necessarily mean that the stimulus delivered to the acoustic nerve will be centrally processed with the result of an auditory perception.

Action Potentials↗

PubMedDate not supplied

Direct and indirect methods used to study arterial blood pressure.

A number of different approaches exist for assessing blood pressure in experimental animals. Here, we briefly consider the traditional indirect (rodent tail-cuff) and direct (saline-filled catheter) methods of blood pressure measurement before going on to describe our experience with blood pressure telemetry in rabbits, rats, and mice. Blood pressure telemetry offers the ability to obtain a high-fidelity recording of blood pressure continuously, for relatively long periods of time, in conscious, freely moving animals, without the limitations of restraint or anaesthesia. Since some drift in telemeter offset and sensitivity are inevitable, recalibration of the telemeter devices immediately before implantation and following explantation is essential to ensure and document the accuracy of the blood pressure measurements. For long-term implantations, verification of the calibration can be performed in vivo, at least in the case of large animals, such as rabbits. Telemetry devices suitable for small animals, such as mice, are also available now, which will facilitate the accurate characterization of blood pressure in transgenic animals. Telemeter implantation methods in mice are presently difficult, with relatively low success rates being reported. However, validation of new methods, such as the insertion of the catheter tip via the carotid artery, may make the technique more widely accessible in the near future.

Animals↗

PubMed1997

The influence of restraint on blood pressure in the rat.

We examined the influence of procedures used in blood pressure measurement on blood pressure and the effects of antihypertensive agents. Subjects were spontaneously hypertensive rats (SHR) and their Wistar/Kyoto (WKY) controls. Blood pressure was recorded by telemetry. Twenty-four h baseline pressure were measured, and the effect of minor handling on blood pressure and heart rate was examined. The influence of restraint such as is used for tail-cuff blood pressures was examined. The effects of three different antihypertensive drugs was also examined in the SHR. In the home-cage environment, the SHRs showed higher systolic blood pressures, but had similar hypertensive responses to minor handling as the WKYs. Both strains had elevated heart rate and blood pressure when restrained in the manner used for tail-cuff readings. The antihypertensive effects of captopril and losartan in the SHR were unchanged when the animals were restrained but the hypotensive effect of hydralazine was greater. These results confirm that significant changes in heart rate and blood pressure can occur as a result of the minor procedures frequently used in blood pressure recording in both SHR and WKY rats. This suggests that telemetry may have significant advantages as a method for continuous blood pressure monitoring. The pharmacological profile of antihypertensive drugs may well be different in animals where telemetry is employed and are not subject to the stresses involved in previous methods of monitoring blood pressure.

Animals↗

PubMed1998

Radiotelemetric versus externalized catheter monitoring of blood pressure: effect of vasopressin in spontaneous hypertension.

The changes in arterial pressure that follow withdrawal of a 3-h intravenous infusion of arginine vasopressin (AVP; 20 ng/kg/min) in spontaneously hypertensive rats (SHR) were monitored by radiotelemetry or conventional externalized femoral arterial catheters connected to pressure transducers. Baseline control arterial pressure was lower in the telemetry group compared to the externalized group. After withdrawal of the AVP infusion, blood pressure fell below preinfusion levels in both groups but the decrease was much less in the telemetry group. Strikingly, absolute blood pressure values recorded both during and after the vasopressin infusion were remarkably similar in the two groups. Responses in rats with externalized catheters implanted 7 days before infusion of AVP, a protocol similar to the telemetry group, were similar to those in rats with catheters implanted 24 h earlier. Blood pressure remained decreased in SHR infused with AVP for several days with complete recovery requiring 6-7 days. In contrast, physical activity decreased only on the first day following withdrawal of the infusion. Thus, the mechanism accounting for the blood pressure decrease must be of a long duration and unrelated to a change in gross physical activity. The results emphasize the value of radiotelemetry for recording blood pressure responses.

Animals↗

PubMed2003

Detection of atrial fibrillation by permanent pacemakers: observations from the STOP AF trial.

Pacemaker telemetry is increasingly being used to infer the presence or absence of arrhythmias in clinical practice. To evaluate the reliability of these data in patients with sick-sinus syndrome, a sub-study of eighteen consecutive patients in the Systematic Trial of Pacing to prevent Atrial Fibrillation (STOP AF) implanted with dual-chamber pacemakers had simultaneous 24-hour Holter recordings and pacemaker telemetry down-loaded. Whilst heart rate data were very similar, telemetry data achieved only 57% sensitivity with 64% specificity for the presence of atrial fibrillation on Holter recording over 24 hours. False-positive results were due to far-field sensing while false-negatives were seen with very short episodes of atrial fibrillation. The pacemaker's anti-tachycardia responses were not specific for the detection of atrial fibrillation. There are very few published reports correlating pacemaker diagnostic data and stored electrograms with external Holter monitoring. We believe that more validation studies of are needed before pacemaker diagnostic data can be used with confidence in clinical practice. It is unlikely that current devices with sophisticated detection algorithms will fail to detect prolonged episodes of arrhythmia and their capacity to confirm events with stored electrograms, intervals and markers reduces the possibility of false-positives, but care must be taken in the interpretation of stored data from devices without these capabilities. Equally, it cannot be assumed that if intracardiac electrograms from one episode confirm the presence of an arrhythmia, that all recorded events have been similarly correctly interpreted. We have shown in a sub-study of STOP-AF that simple mathematical models using heart rate bin analysis are not reliable for detection of arrhythmias with short durations. Despite these limitations, the potential of implanted pacemakers to record cardiac rhythm and trends, such as heart-rate variability, over time remains an exciting prospect, particularly in guiding individual patient therapy.

Atrial Fibrillation↗

PubMed1991

[The programming of cardiac pacemakers--wish and reality].

To test the extent and quality of pacemaker programming, 340 programmable pacemakers were selected out of 1,204 impulse generators removed post-mortem. Their actual program was compared with the nominal parameters when first delivered. 177 (52.1%) of the 340 pacemakers still had the same parameters as on delivery. The multiply programmable impulse generators with telemetry were more frequently programmed (61.2%) than the simple programmable ones (43.0%) or the multiply programmable ones without telemetry (43.7%). Rate was the most frequently programmed parameter, followed by impulse amplitude, sensitivity and impulse duration. Refractory time and hysteresis were only rarely changed from the initial state. Apparently, programmability was not thought to be important enough. Programming without telemetry was seemingly too complicated. The reasons for this attitude should be investigated so that the discrepancy between wishes and reality can be overcome.

Equipment Design↗

PubMedDate not supplied

Supervised exercise and electrocardiographic monitoring during cardiac rehabilitation. Impact on patient care.

PURPOSE: To determine the frequency of medical problem detection during supervised cardiac rehabilitation exercise, and to assess its impact on patient care alteration. METHODS: Six hundred sixty-six cardiac participants (388 in Phase II and 278 in Phase III) were studied during a 1-year period (1989-1990). The supervisory staff recorded all phone calls made to referring physicians regarding individual patient problems identified during exercise sessions including subsequent alteration in patient care. RESULTS: Overall, 112 of 666 (17%) of the patients had problems detected that prompted calls to referring physicians. There was 0.009 call per patient exercise hour, compared to 0.002 call per patient exercise hour in the Phase II and Phase III patients, respectively, P = .0001. Although Phase II patients had a higher uncorrected arrhythmia call frequency compared to the Phase III patients, arrhythmia call frequency was higher in Phase III patients, when corrected for the number of monitored exercise hours (P = .02). Fifty-five percent of calls resulted in patient care alteration, and telemetry-related calls and nontelemetry-related calls resulted in a similar proportion of patient care alteration. Overall, 11% (73 of 666) of patients had alteration of their care, of which 4% (24 of 666) resulted from telemetry-related calls. Clinical variables between the patients with calls versus the patients with no calls demonstrated that the call group were older, and had a more frequent history of hypertension. CONCLUSION: Medically supervised cardiac rehabilitation with and without telemetry monitoring detects problems that lead to alteration in medical care. Older patients have more problems detected. Medical problem detection may contribute to the beneficial impact of cardiac rehabilitation observed in randomized trials.

Age Factors↗

PubMed1998

An externally powered, multichannel, implantable stimulator-telemeter for control of paralyzed muscle.

An implantable integrated stimulator and telemetry system has been developed. The system is capable of fulfilling the stimulus and telemetry needs of advanced functional neuromuscular stimulation (FNS) applications requiring multiple channels of stimulation and multiple channels of sensor or biopotential sensing. This system provides a command control structure, an inductive radio frequency link providing power to the implant device as well as two-way transcutaneous communication, an ASIC for decoding the command and for providing functional control within the implant, and modular circuitry providing the application specific implant functions. Biocompatible hermetic packaging, lead systems, and in-line connectors suitable for long-term implantation, provide encapsulation for the circuitry and access to the electrodes and sensors used in the application. The first implant configuration realized from this modular system is targeted for clinical implementation in persons with tetraplegia at the C6 level for restoration of hand function, using wrist position as the command control source. The implant device realized has ten channels of stimulation and telemetry used to control and sense a joint angle transducer implanted in the radio-carpal joint of the wrist. A prototype device has been fabricated and is undergoing testing in an animal.

Algorithms↗

PubMed2006

Robust hierarchical state-space models reveal diel variation in travel rates of migrating leatherback turtles.

1. Biological and statistical complexity are features common to most ecological data that hinder our ability to extract meaningful patterns using conventional tools. Recent work on implementing modern statistical methods for analysis of such ecological data has focused primarily on population dynamics but other types of data, such as animal movement pathways obtained from satellite telemetry, can also benefit from the application of modern statistical tools. 2. We develop a robust hierarchical state-space approach for analysis of multiple satellite telemetry pathways obtained via the Argos system. State-space models are time-series methods that allow unobserved states and biological parameters to be estimated from data observed with error. We show that the approach can reveal important patterns in complex, noisy data where conventional methods cannot. 3. Using the largest Atlantic satellite telemetry data set for critically endangered leatherback turtles, we show that the diel pattern in travel rates of these turtles changes over different phases of their migratory cycle. While foraging in northern waters the turtles show similar travel rates during day and night, but on their southward migration to tropical waters travel rates are markedly faster during the day. These patterns are generally consistent with diving data, and may be related to changes in foraging behaviour. Interestingly, individuals that migrate southward to breed generally show higher daytime travel rates than individuals that migrate southward in a non-breeding year. 4. Our approach is extremely flexible and can be applied to many ecological analyses that use complex, sequential data.

Animal Migration↗

PubMed1982

An assessment of radiotelemetry in the monitoring of labour.

Conventional and telemetric monitoring of labour were compared in a randomized study of 200 patients to assess the effect on the pattern of labour, outcome and attitude of the patients. All the telemetry patients had the option of mobility, but only 45% elected to get out of bed, and then often only for short periods. No clear physical benefits accrued from voluntary mobility. Ambulant patients who had spontaneous deliveries had a longer second stage and more of their babies were slow to establish regular respiration. Quantitative subjective assessments of pain, anxiety and comfort were made. Primigravidae with telemetric monitoring who chose to get out of bed had higher pain scores than primigravidae monitored conventionally, but anxiety scores were highest among primigravidae with telemetry who elected to stay in bed. There was a significant bias towards increased anxiety in the lower social classes. Primigravidae gained more reassurance from monitoring than did multigravidae, but there were no differences resulting from whether or not the recording apparatus was within the patients' view. Multigravidae who had experienced both forms of monitoring preferred telemetry because they felt less restricted and less anxious.

Anxiety↗

PubMed1984

Simultaneous atrial and ventricular electrogram transmission via a specialized single lead system.

No telemetrically monitorable pacemakers are capable of detecting and transmitting the complete electrogram (EGM) during normal and paced rhythms, although some are capable of detecting and transmitting either the P- or R-wave. A new lead and telemetry-pacemaker system has been developed that permits the transmission of the complete EGM and is not adversely affected by pacemaker outputs or after-potentials. Electrodes are placed in the right ventricle and atrium to optimize EGM detection. These A-V data probe electrodes are electrically separate from the pacing-sensing electrodes but are structurally part of a coaxial ventricular lead that is no larger than a conventional bipolar lead (2.3 mm). The telemetry system is also compatible with telephone monitoring systems. The system has consistently demonstrated its ability to detect accurately the EGM during normal sinus rhythms and does not affect atrial, ventricular, or A-V sequential pacing. In addition, this system can detect and transmit EGM abnormalities, including ectopic beats, retrograde conduction, and ischemic changes. A-V data leads with telemetry monitored VVI pacemakers have been implanted in dogs for over two years. This system will provide the means to detect and telemetrically record noninvasively the entire normal and abnormal EGM, even in pacer dependent patients. (PACE, Vol. 7, November-December, 1984).

Animals↗

PubMed1990

Inappropriate discharges by the implantable cardioverter defibrillator during postoperative testing: implications for intraoperative assessment.

Inappropriate shocks were delivered to a patient while in sinus rhythm by an implantable cardioverter defibrillator (ICD) during routine prehospital discharge testing. This was induced by the standard programmer when the "read" telemetry sequence was initiated. The ICD was removed and found to suffer from electrical artifact that was sensed as ventricular tachycardia during telemetry. To avoid inadvertent telemetry-induced shocks during routine testing, all ICDs should be interrogated, using a standard programmer, intraoperatively, with the unit in "defibrillation on" mode.

Aged↗

PubMed1998

Noise detection during bradycardia pacing with a hybrid nonthoracotomy implantable cardioverter defibrillator system: incidence and clinical significance.

The purpose of this study was to prospectively evaluate the incidence of noise detection during bradycardia pacing by an FDA approved hybrid nonthoracotomy ICD system. An illustrative case report which prompted this investigation is provided. Backup bradycardia pacing by tiered therapy cardioverter defibrillators has been useful in preventing postshock bradycardia and occasionally for chronic rate support in bradycardic patients. Unexplained "noise" detected by real-time telemetry has been previously described during bradycardia pacing by a device utilizing automatic gain control for sensing. Eighteen patients were prospectively evaluated for noise detection during ventricular pacing by the ICD. Real-time telemetry was analyzed with each patient: (1) supine, (2) supine with deep inspiration/expiration, (3) supine during Valsalva, and (4) during a change in position from supine to sitting. Analysis of pacing threshold and lead impedance was made in each patient. Eleven of 18 patients had noise detected on real-time telemetry during bradycardia pacing. In 10 patients this was noted during deep inspiration/expiration, in 2 during Valsalva maneuver, and in 5 with position change. There was no evidence in any patient of lead malfunction nor any difference in pacing threshold or lead impedance between patients with noise detected versus those without it. Noise detection by an approved hybrid ICD system is common and may be due to the automatic gain control which maximizes sensitivity during bradycardia pacing. This may lead to clinically significant events, with both suppression of bradycardia pacing and triggering of tachycardia therapy in the absence of ventricular tachyarrhythmias in pacemaker-dependent patients.

Aged↗

PubMed1982

Human interdental plaque-pH data and rat caries tests: results with the same substances.

Interdental plaque-pH telemetry measures, in vivo, H-ion concentration at the level of the enamel surface under an undisturbed layer of plaque. It is better suited to test non- or hypo-acidogenic products than are rat caries tests. These products can, with a very high probability, be considered non- or hypocariogenic ("safe, or friendly, for teeth"), no matter how frequently they are consumed. Plaque-pH telemetry is poorly suited for judging the effectiveness of agents directed at enamel - e.g., topical fluoride, remineralizing solutions, etc. - or agents which may have long-term effects on plaque composition. Plaque-pH telemetry is able to demonstrate the effects of different meal patterns and the form and texture of foods on oral clearance and plaque pH.

Acids↗

PubMed2001

Continuous-display four-channel electroencephalographic monitoring in the evaluation of neonates with paroxysmal motor events.

The objective of this study was to determine the value of continuous-display four-channel electroencephalographic (EEG) monitoring to distinguish epileptic front nonepileptic paroxysmal motor events. Five full-term neonates with paroxysmal motor events were included in the study. Nurses were instructed to print contiguous pages of the continuous-display four-channel EEG monitoring and to activate the event marker on the simultaneously conducted continuous video-EEG telemetry unit during each paroxysmal motor event. The printouts from the continuous-display four-channel EEG monitoring were interpreted and compared with the corresponding segments of continuous video-EEG telemetry. Thirty paroxysmal motor events were captured. Sixteen paroxysmal motor events were epileptic, and 14 were nonepileptic. The interpretation of the printouts of the continuous four-channel EEG monitoring concurred with an independent interpretation of the corresponding video-EEG telemetry segments in all of the events. Continuous-display four-channel EEG monitoring is a valuable tool in the evaluation of neonates with paroxysmal motor events since it reliably distinguishes epileptic and nonepileptic events.

Electroencephalography↗

PubMed2000

Telemetric monitoring of blood pressure in freely moving mice: a preliminary study.

This paper describes for the first time the possibility for recording the systolic pressure (SP), diastolic pressure (DP), and the mean arterial pressure (MAP) as well as the heart rate (HR) and locomotor activity (LA) in freely moving mice, using a commercially available telemetry and data acquisition system. The system comprises a new, small radio-telemetry transmitter implanted in the peritoneal cavity, a receiver board placed underneath the home cage, a multiplexer and a computer-based data acquisition system. The signals from the receiver were consolidated by the multiplexer and were stored and analysed by the computer. The telemetered pressure signals (absolute pressure) were corrected automatically for changes in atmospheric pressure measured by an ambient pressure monitor. The effects of implantation on animal behaviour, and, after the animals had recovered, the effects of handling on the SP, DP, MAP and HR were examined. The radio-telemetry system for recording the SP, DP, MAP and HR provides an accurate and reliable method for monitoring the direct effects of handling on SP, DP, MAP and HR. In addition, by using this new blood pressure (BP) transmitter, we maintain that BP measurements in freely moving mice are more efficient, reliable, and less labour-intensive than the measurement techniques described in the literature thus far.

Animals↗

PubMed1999

Diurnal variations of blood pressure in dogs.

Using the telemetry system, we measured the blood pressure (BP) invasively in seven adult mongrels while unanesthetized and unbound. Post-operative BP after implanting the telemetry BP transmitter showed temporarily high values due to the invasive nature of the surgery. It was, however, observed that BP gradually decreased thereafter, and showed settled trends from the eighth day post-operatively. When we took the average of the systolic, mean and diastolic BP at hourly intervals for each of the dogs once their BP had settled, a twin peak diurnal variation (at 8:00 and 19:00) was observed. Moreover, significantly high values (p < 0.05) were identified in active state compared with when sleeping or at rest. The 24 hr BP measured by the telemetry system in seven normal dogs resulted in the following values: systolic 123.4 +/- 7.9 mmHg, mean 91.1 +/- 5.6 mmHg, and diastolic 74.5 +/- 4.9 mmHg.

Animals↗