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PubMed1989

Perioral force measurement by a radiotelemetry device.

A telemetric method was developed to monitor the active and passive perioral forces exerted on the maxillary dental arch. The system consists of intraoral and extraoral units. An electromagnetic coupling between intraoral and extraoral coils supplies the power of the intraoral unit and transmits the signals induced by variations in perioral forces. The force sensor has a diameter of 6 mm, a thickness of 1 mm, and is constructed of an 0.08 mm thick cantilever beam to which semiconductor strain gauges are cemented. Clinical application of the system was tested in four adult subjects. The forces on the labial surface of an upper central incisor were 1.5 gm/cm2 during rest, 10.9 gm/cm2 during swallowing, and 5.0 gm/cm2 during speech; the corresponding lingual forces were 4.0 gm/cm2, 19.1 gm/cm2, and 13.9 gm/cm2, respectively. Lingual forces were always higher than labial forces. The telemetry system can be used to monitor up to 6 hours of continual variations in perioral forces.

Adult↗

PubMed1992

A radiotelemetry system for chronic measurement of blood pressure and heart rate in the unrestrained rat validation of the method.

Chronic measurements of systemic arterial blood pressure and heart rate via a chronically implanted telemetric transmitter in unrestrained rats, was validated in a three-phase study. In the first part, week-to-week variability of systolic, diastolic, and mean arterial pressures, and heart rate was found to be minimal over the course of nine weeks. In the second part, the reproducibility of cardiovascular response to three successive administration of sotalol, an antihypertensive agent, was studied. In the last part, cardiovascular parameters determined by telemetry were compared to those obtained by direct arterial catheterization and showed a good linear correlation between those two methods.

Administration, Oral↗

PubMed1996

In vitro load measurement using an instrumented spinal fixation device.

An AO spinal fixateur interne was modified to study the effects of a corpectomy on implant performance. A hermetically sealed cartridge containing strain gauges and an inductively powered telemetry unit was integrated into the threaded portion of the original implant. Five cadaveric spines were instrumented with the modified implant spanning a single lumbar vertebra. The spines were tested in axial compression, torsion, flexion, extension and lateral bending. Measurements of the three forces and moments within the implant were performed in the intact spine and repeated following a corpectomy and corpectomy plus complete posterior ligamentous injury. The bending moment, increased following corpectomy in all testing modes. The largest increase was in the flexion bending moment, which increased from 155 Nmm to 3328 Nmm following corpectomy.

Aged↗

PubMed2005

Clinical assessment of the entry into neurological state in rat experimental African trypanosomiasis.

Human African trypanosomiasis, caused by Trypanosoma brucei (T.b.) gambiense or rhodesiense, evolves in two stages: haemolymphatic stage and meningo-encephalitic stages, the latter featuring numerous neurological disorders. In experimental models infected with diverse T.b. sub-species, body weight (BW) loss, drop in food intake (FI), and hypo-activity after an asymptomatic period suggest the occurrence of a similar two-stage organization. In addition to daily measurement of BW and FI, body core temperature (T(co)) and spontaneous activity (SA) were recorded by telemetry in T.b. brucei-infected rats. After a 10--12-day symptom-free period, a complex clinical syndrome occurred suddenly. If the animal survived the access, the syndrome re-occurred at approximately 5-day intervals until death. The syndrome was made of a drop in FI and BW, a sharp decrease in T(co) and a loss of SA, suggesting a brisk alteration of the central nervous system functioning. Such events confirm the existence of a two-stage disease development in experimental trypanosomiasis. The entry into the second stage is marked by the occurrence of the first access, BW follow-up being essential and often sufficient its determination.

Animals↗

PubMed2006

Increased salt-sensitivity in endothelial nitric oxide synthase-knockout mice.

BACKGROUND: Although impaired nitric oxide production contributes importantly to salt-sensitivity, the role of the endothelial isoform of nitric oxide synthase (eNOS) has received little attention. In the present study we compared the effects of a high-salt diet on the blood pressure response of eNOS knockout (eNOS-/-) and control (eNOS+/+) mice. METHODS: Mean arterial pressure (MAP), heart rate, pulse pressure, and activity levels were recorded by telemetry in mice fed a regular-salt diet (0.7% NaCl) followed by 6 weeks on either a high-salt (8% NaCl) or regular-salt diet. RESULTS: The eNOS-/- mice exhibited a 15% increase in MAP and a 2- to 2.5-fold increase in salt-sensitivity relative to the control strain. Salt-induced increases in MAP were well sustained in eNOS-/-, whereas in eNOS+/+ the initial increase was biphasic. The effects of salt on MAP were particularly pronounced during locomotor activity, during the dark phase, and at the peak levels of MAP recorded over the course of the day. The high-salt diet also led to a transient increase in the proportion of time spent active. Levels of heart rate and pulse pressure were relatively unaffected by the high-salt diet. CONCLUSION: The eNOS-/- mice exhibit an increased blood pressure response to a high-salt diet. This finding suggests that eNOS normally provides an important contribution to the body's adaptation to a salt load and that reduced production of NO by eNOS may promote salt-sensitivity and salt-induced hypertension.

Animals↗

PubMed2004

Automatic analysis of auditory nerve electrically evoked compound action potential with an artificial neural network.

The auditory nerve's electrically evoked compound action potential is recorded in deaf patients equipped with the Nucleus 24 cochlear implant using a reverse telemetry system (NRT). Since the threshold of the NRT response (NRT-T) is thought to reflect the psychophysics needed for programming cochlear implants, efforts have been made by specialized management teams to develop its use. This study aimed at developing a valid tool, based on artificial neural networks (ANN) technology, for automatic estimation of NRT-T. The ANN used was a single layer perceptron, trained with 120 NRT traces. Learning traces differed from data used for the validation. A total of 550 NRT traces from 11 cochlear implant subjects were analyzed separately by the system and by a group of physicians with expertise in NRT analysis. Both worked to determine 37 NRT-T values, using the response amplitude growth function (AGF) (linear regression of response amplitudes obtained at decreasing stimulus intensity levels). The validity of the system was assessed by comparing the NRT-T values automatically determined by the system with those determined by the physicians. A strong correlation was found between automatic and physician-obtained NRT-T values (Pearson r correlation coefficient >0.9). ANOVA statistics confirmed that automatic NRT-Ts did not differ from physician-obtained values (F = 0.08999, P = 0.03). Moreover, the average error between NRT-Ts predicted by the system and NRT-Ts measured by the physicians (3.6 stimulation units) did not differ significantly from the average error between NRT-Ts measured by each of the three physicians (4.2 stimulation units). In conclusion, the automatic system developed in this study was found to be as efficient as human experts for fitting the amplitude growth function and estimating NRT-T, with the advantage of considerable time-saving.

Cochlear Implants↗

PubMed2005

Cardiovascular and autonomic nervous functions during acclimatization to hypoxia in conscious rats.

The time courses of changes in cardiovascular and autonomic nervous functions during acclimatization to hypoxia were studied in conscious Sprague-Dawley rats. The animals were kept under a 12:12-h light-dark cycle and exposed to hypoxia (1 atm, 10% O2). Implanted telemetry transmitters were used to record blood pressure (BP). Changes in heart rate (HR) and BP were monitored over a 21-day period, and variations before and during hypoxia were analyzed using the wavelet transform method. The HR, high-frequency power of HR variability (HR-HF) and low-frequency power of BP variability (BP-LF) were all significantly increased after 1 h of hypoxia, whereas the LF/HF ratio of HR variability did not change. After this initial increase, both HR and the BP-LF were found to decrease. On the first day of hypoxia, HR and BP-LF values were significantly lower than those of the control rats, whereas the HR-HF was higher. Subsequently, these values altered so that they were similar to the control after 14 days of hypoxia. In addition, the amplitude of diurnal variation in HR was reduced during hypoxia. These results suggest that a sequence of dynamic interactions between sympathetic and parasympathetic nervous activities might have important roles in the regulation of cardiovascular function during acclimatization to hypoxia.

Acclimatization↗

PubMed2004

Changes in thermal preference, sleep-wakefulness, body temperature and locomotor activity of rats during continuous recording for 24 hours.

This study was aimed at correlating diurnal changes in thermal preference of rats with their body temperature (Tb), sleep-wakefulness (S-W) and locomotor activity (LMA). Electroencephalogram (EEG), electromyogram (EMG), electrooculogram (EOG) and Tb were recorded by telemetry, while an activity monitor measured LMA and thermal preference. A special environmental chamber, which was designed and fabricated, enabled for the first time, simultaneous measurement of thermal preference, along with S-W and Tb. S-W, thermal preference and LMA were recorded continuously in six adult male Wistar rats, for 24 h, for 3 days, and Tb with thermal preference and LMA were recorded for another 3 days. LMA and Tb were higher at night than during day. The rats slept less during the night time. Increased frequency of sleep episodes contributed towards increased sleep during day time. They preferred an ambient temperature (Tamb) of 24 degrees C at night and 27 degrees C during the day. Though the preference for higher Tamb during day time coincided with increased sleep, the rats did not move over to higher Tamb prior to the onset of sleep episodes. Though the diurnal alterations in sleep, Tb and LMA were similar to those reports from animals kept in constant Tamb, the day-night variation of paradoxical sleep (PS) was exaggerated when the rats selected their own preferred Tamb.

Analysis of Variance↗

PubMed2004

Dissociation of hyperalgesia from fever following intracerebroventricular administration of interleukin-1beta in the rat.

Interleukin-1beta (IL-1beta) is a cytokine that contributes to the hyperalgesia, inactivity, and fever associated with illness. These three components of the illness response occur simultaneously following peripheral administration of IL-1beta. The objective of the present study was to determine whether hyperalgesia, inactivity, and fever correspond following central administration. Rats were injected with IL-1beta (0.05 pg-50 ng/10 microl) into the lateral ventricle and core body temperature and activity were assessed for 5.5 h using radio telemetry while rats remained in their home cage. Rats were removed from the cage periodically to assess nociception by measuring the latency for hindpaw withdrawal to radiant heat. The two highest doses of IL-1beta (5 and 50 ng) caused an increase in core body temperature and a decrease in activity beginning 105 min following administration. No change in nociception was evident at any time after administration of IL-1beta regardless of dose. These data indicate that the hyperalgesia associated with fever is triggered by a peripheral, not a central action of IL-1beta, presumably by activation of vagal afferents.

Animals↗

PubMed2005

Lower core body temperature and attenuated nicotine-induced hypothermic response in mice lacking the beta4 neuronal nicotinic acetylcholine receptor subunit.

Diverse physiological and pathological effects of nicotine, including the alteration of body temperature, are presumably mediated by neuronal nicotinic acetylcholine receptors (nAChR). Previous studies have suggested the involvement of distinct nAChR subunits in nicotine-induced thermoregulation. We studied genetically manipulated knockout mice lacking the alpha7, alpha5 or beta4 subunit genes, in order to assess the effects of subunit deficiency on temperature regulation. Using a telemetry system, core body temperature was monitored continuously prior to and following nicotine administration in mutant mice and in wild-type littermates. Mice lacking in the beta4 nAChR subunit gene had significantly lower baseline core body temperature than all other mouse strains studied. beta4 null mice also demonstrated a reduced nicotine-induced hypothermic response and impaired desensitization following repeat nicotine exposure. These findings suggest the involvement of the beta4 nAChR subunit in both core body temperature homeostasis and nicotine-elicited thermo-alterations in mice.

Animals↗

PubMed2005

Endothelin receptor--a blockade decreases ventricular arrhythmias after myocardial infarction in rats.

OBJECTIVE: Endothelin-1 (ET-1) production increases during acute myocardial infarction (MI) and may contribute to the genesis of ventricular tachycardia (VT) and ventricular fibrillation (VF). However, the antiarrhythmic effects of ET-1 receptor blockade, examined shortly after MI, have been debated. In the present study, we examined the effects of such treatment on VT/VF during the first 24 h post-MI. METHODS: Thirty-five Wistar rats (223+/-22 g) were randomly allocated to either the ET-1 receptor-A (ETA) antagonist BQ-123 (0.4 mg/kg, BQ-123 group, n=17), or normal saline (control group, n=18) and were subjected to coronary artery ligation. A single-lead electrocardiogram was continuously recorded for 24 h post-MI, using an implanted telemetry system, and episodes of VT/VF were analyzed. Monophasic action potential (MAP) recordings were obtained from the left (LV) and right (RV) ventricular epicardium at baseline, 5 min after treatment and 24 h post-MI. RESULTS: There were 15.94+/-19.35 episodes/h/rat of VT/VF in the control group and 1.66+/-2.22 in the BQ-123 group (p=0.010), resulting in a lower (p=0.030) arrhythmic mortality in treated animals. The mean episode duration was 7.40+/-7.16 s for the control group and 2.30+/-1.37 s for the BQ-123 group (p=0.011). The maximum decrease in VT/VF was observed during the 1st, 5th and 6th hours post-MI. In the control group, LV MAP duration increased 24 h post-MI, displaying an increased beat-to-beat variation, but remained unchanged in the BQ-123 group. CONCLUSION: Acute ETA blockade reduces the incidence of VT/V F during the first 24-h post-MI in the rat, through a decrease in the dispersion of repolarization.

Action Potentials↗

PubMed2006

Evaluation of cardiovascular effects of caffeine using telemetric monitoring in the conscious rat.

Caffeine (1,3,7 trimethylxanthine) affects the cardiovascular system, with potential toxic effects ranging from a moderate increase in heart rate to more severe cardiac arrhythmias. Telemetry transmitters were implanted in Wistar rats in the peritoneal cavity with a pressure catheter in the aorta and electrodes for electrocardiogram (ECG) recording subcutaneously. After a single oral administration of saline, each rat was administered single oral doses of 5, 15 and 45 mg/kg b.w. of caffeine. Caffeine was found to induce, to various degrees, a dose-dependent early increase in spontaneous physical activity, heart rate, dp/dt and systolic-diastolic blood pressure. No arrhythmias or visual changes were observed in the ECG complex. High doses induced more strong responses and of longer duration. The increase in systolic blood pressure at the median dose remained in the rats until 20 h after administration. However, the highest dose of caffeine (45 mg/kg b.w.) induced a biphasic response, with an early and pronounced increase in body temperature, spontaneous physical activity, systolic and diastolic blood pressure that later decreased, except for the systolic blood pressure. The results show that the dose level for long-lasting signs of intoxication to develop in the rat, in terms of effects on spontaneous physical activity, body temperature and cardiovascular function, was reached after a single oral dose of caffeine at 45 mg/kg b.w.

Administration, Oral↗

PubMed2006

A comparison of muscle activity and heart rate response during backward and forward walking on an underwater treadmill.

This investigation compared muscle activities and heart rate (HR) responses while subjects walked backward or forward in water, with and without a water current. Ten healthy males (23.5+/-1.4 years) volunteered for the study. Surface electromyography (EMG) was used to evaluate muscle activities while the subjects walked in water, immersed to the level of the xiphoid process. HR responses were monitored continuously by a telemetry method. A "Flowmill" was used for this study, which involves a treadmill at the base of a water flume. Measurement of maximal voluntary contraction (MVC) of each tested muscle was undertaken prior to gait analysis. The %MVCs obtained from the paraspinal muscles, vastus medialis and tibialis anterior were all significantly greater when walking backward than when walking forward, for every experimental condition (P<0.05). HR responses tended to be greater while walking backward than when walking forward, with a statistical significance at fast speed (P<0.05). In conclusion, walking backward in water resulted in significantly greater muscle activation of the paraspinal muscles, vastus medialis and tibialis anterior compared with walking forward in water. These findings may be helpful in developing water-based exercise programs.

Adult↗

PubMed2004

Doppler-guided regulation of a telemetrically operated adjustable pulmonary banding system.

OBJECTIVES: We report on the Doppler-assessed regulation of an adjustable pulmonary artery band (PAB) in an animal model and in our first group of patients. BACKGROUND: Indications for pulmonary artery banding have expanded to include patients requiring a late arterial switch. A telemetry-operated, fully implantable, adjustable PAB system (FloWatch- PAB, Endoart SA, Lausanne, Switzerland) has been developed to facilitate these operations. METHODS: The device was implanted in 13 minipigs (age one to five months, weights 3.2 to 12.0 kg). The main study was performed on nine minipigs with adjustments of the PAB at implantation and at 1, 3, 5, 8, and 12 weeks after, assessed by Doppler pressure gradients. Explanation was performed 12 weeks after surgery. A long-term histology study (6 months and 14 months after surgery) was done on the other four minipigs. After approval by the ethics committee, the device was implanted in eight patients with weights between 2.8 and 9 kg to decrease pulmonary blood flow and pressure and to retrain the left ventricle before arterial switch. The device was progressively tightened, with increasing transband Doppler gradients. Follow-up was one to three months. RESULTS: An excellent correlation between transbanding systolic pressure gradient and degree of PAB constriction was encountered in the minipig study as well as in the human setting. No early or late deaths or reoperations occurred. Malfunction of the device was noted in three of 21 implanted devices. Two were related to surgically inflicted damage at implantation and one to an electronic problem that was fixed by resetting the control device. CONCLUSIONS: The device offers a Doppler-controllable adjustment of pulmonary blood flow. It permits controlled tightening and release of the band, which improves perioperative and postoperative courses and decreases surgical interventions to adjust tightness of the band. It allows a protracted occlusion protocol, which may provide the best effect on retraining the left ventricle.

Animals↗

PubMed2005

Knee mechanics: a review of past and present techniques to determine in vivo loads.

This review article evaluates various techniques that have been used to determine in vivo loads in the human knee. Two main techniques that have been used are telemetry, which is an experimental approach, and mathematical modeling, which is a theoretical approach. Telemetric analyses have previously been used to determine the in vivo loading of the human hip and more recently evaluated in the determination of in vivo knee loads. Mathematical modeling approaches can be categorized two ways; those that use optimization techniques to solve an indeterminate system and those that utilize a reduction method that minimizes the number of unknowns, keeping the system solvable as the number of equations of motion are equal to the number of unknown quantities. More recently, we have developed an approach that relies fully on the use of in vivo data from fluoroscopy, CT scanning, magnetic resonant imaging and a revised motion analysis technique that involves only two markers on each rigid body. A review of all techniques revealed a wide range of forces at the human knee, ranging from 1.9 to 7.2 times body weight during level walking.

Algorithms↗

PubMed2006

Wireless Holter transmission in suspected dysrhythmias.

BACKGROUND: In patients with a history of possible dysrhythmias, documentation of an episode is mandatory before any form of treatment is given. Holter recordings with wireless telemetry offer the possibility of continuously recording electrocardiograms for days or even weeks with instantaneous analysis of the data in the physician's office. METHODS: Thirty-seven patients (20 male; median age, 8.4 years; range, 0.1-22 years), were investigated by using a telemetric Holter system (M120, Schiller, Switzerland), that is, intermittent transmission of the electrocardiographic data to a remote server using cell phone frequencies, with a median duration of the recordings of 6.5 days (range 1-42 days). RESULTS: Recording quality was sufficient in all patients. Problems were related to electrode disconnections only, which were adjusted by contacting the patients. Twenty-eight of 37 recordings showed decisive findings. Of the 28 patients, no treatment was indicated in 16 patients, as subjective symptoms did not correlate with dysrhythmias; psychotherapy was indicated in 2 patients; antiarrhythmic medication was initiated or intensified in 5 patients; radiofrequency ablation was successfully performed in 5 patients; and 1 patient received an ICD. In 6 of 9 patients with negative Holter findings, a loop recorder implantation (Medtronic, Minneapolis, Minn) was indicated. In 1 patient, no dysrhythmias were recorded; however, when invasively investigated, ventricular tachycardia was detected and successfully treated by radiofrequency ablation. In 2 patients, no decision has been made to date. CONCLUSIONS: Wireless Holter recordings are useful in detecting dysrhythmias with rare occurrence, are less expensive and less invasive compared with implantable loop recorders, and offer the patient rather wide geographic ranges with sufficient signal quality.

Adolescent↗

PubMed2006

Electrocardiogram on a chip: overview and first experiences of an electrocardiogram manufacturer of medium size.

The integration of an electrocardiogram (ECG) device into a chip is already well known in the field of implanted devices, such as pacemakers. For noninvasive electrocardiology, this approach has not been used on a broad scale commercially. The extension of electrocardiology to telemetry, home care, and special applications as in magnetic resonance imaging has spawned a new interest in highly miniaturized ECG devices. In our company, we are aiming for using highly integrated devices exactly in these fields. On one hand, the home monitoring market ("eHealth," "pHealth") requires small and lightweight devices ("ECG in an electrode"); on the other hand, the use of an ECG device within a hostile environment as in an magnetic resonance imaging machine with strong electromagnetic fields requires small dimensions of the device. Of these 2 fields, the one of home monitoring is the most promising. There is a large population in need of such monitoring (eg, patients with congestive heart failure), and the cost issue in medical care drives the market in this direction. Projects in both fields will be presented as well as the first experiences as a middle-sized manufacturer in trying to produce an integrated ECG "device."

Biotechnology↗

PubMed2026

Reliability of resting heart rate measurements in atrial fibrillation.

BACKGROUND: Heart rate (HR) control in atrial fibrillation (AF) is commonly guided by resting HR measurements, usually with 12‑lead ECG or in-office pulse palpation. OBJECTIVES: We aimed to assess the reliability of resting HR measurements in AF patients with long-term ambulatory ECG and activity monitoring. METHODS: We included patients who had recorded a full-disclosure ambulatory ECG with a mobile cardiac telemetry device equipped with an accelerometer (PocketECG, MEDICALgorithmics, Poland), with at least 95% AF. Resting HR samples (≤20 per individual/day) were collected as 10-s daytime (8 am to 8 pm) measurements after ≥10 min of rest. These samples were compared to each individual's mean daytime resting HR. RESULTS: In 832 patients (median age 77 (interquartile range (IQR) 69-83) years, 42% women) with a median registration duration of 13 days (IQR 7-22), the population mean daytime resting HR was 85 (±15) beats per minute (bpm). A single resting HR differed from the mean daytime resting HR by a mean of ±10.4% (IQR 3.6-14.4%). When the mean daytime resting HR was ≥110 bpm, 29% of resting HR samples were < 110 bpm, and when the mean daytime resting HR was 80-109 bpm,11% of samples were ≥ 110 bpm. Resting HR measurement variability decreased to 5.3% (IQR 1.9-7.5%) when four resting HR samples were averaged. CONCLUSION: In patients with AF, a single resting HR measurement often differs substantially from the mean daytime resting HR. When a precise measurement is clinically relevant, repeated resting HR sampling or ambulatory monitoring can address this measurement imprecision.

Humans↗