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At least 1,261 records · Page 70Linked to original sources
PubMed1997

Data compression of fetal Doppler ultrasound audio signals using zero-crossings analysis.

This paper outlines a method of reducing the data rate for transmitting fetal Doppler ultrasound audio signals. A specific application is cited where compression of the fetal Doppler signal is required to transmit information to cardiotocographs (CTGs) using radio telemetry. The method involves splitting the signal into amplitude and frequency components. The amplitude is represented by samples of the signal envelope whilst the frequency information is represented by the number of zero-crossings within fixed intervals (windows). With a careful choice of window size, it is shown that this method can be used to reproduce the signal with no audible difference when compared with the original waveform. A reduction in data rate of 15:1 is achieved.

Algorithms↗
PubMed2002

Electroencephalographic measurement of possession trance in the field.

OBJECTIVES: To verify the utility of a portable electroencephalogram (EEG) measurement system developed for investigating spontaneous EEG from vigorously moving healthy subjects in a possession trance under a natural condition. METHODS: A portable multi-channel EEG telemetry system was developed to record the EEGs of 3 healthy male Balinese while they were performing a ritual dedicatory drama in the field. After reducing extraneous artifacts using a digital filter, the EEGs and their power spectra were analyzed in terms of evolution from one state to another. RESULTS: During the drama, one of the subjects became possessed while the others did not. The EEG of the possessed subject did not show any pathological findings including epileptic discharges, but indicated enhanced power in the theta and alpha frequency bands during the trance. This finding was not observed in the other two subjects, who did not go into trances, with no pathological EEG findings. CONCLUSIONS: The measurement system and data analysis methods we developed have allowed us, for the first time, to obtain an EEG from healthy subjects who are vigorously moving while in a possession trance. The present technique enables us to use a spontaneous EEG as a marker of the underlying physiology of a state of possession trance.

Adult↗
PubMed2001

Smoothed pseudo Wigner-Ville distribution as an alternative to Fourier transform in rats.

Techniques for examining signals in the time and frequency domains are well-established tools. These tools have their limitations; they tell us in a broad sense where the signal component exists in the frequency domain, but they do not tell us how its frequency characteristics change over time. The time-frequency has become a powerful alternative for the analysis of signals. Among various time-frequency distribution methods, one of the most studied is the Wigner-Ville distribution. The aim of this study was to evaluate in conscious rats smoothed pseudo Wigner--Ville distribution (SPWVD) as an alternative to the fast Fourier transform (FFT) in RR intervals and in systolic blood pressure (SBP), before and after adrenergic and cholinergic receptor blockade. Fourteen Wistar rats equipped with telemetry probe were evaluated: (1) under control conditions; (2) after injection of saline (100 microl kg(-1) i.v.); (3) after atenolol (1 mg kg(-1) i.v.); (4) after atropine methyl nitrate (0.5 mg kg(-1) i.v.); and (5) after phentolamine (5 mg kg(-1) i.v.). FFT and SPWVD were applied to RR intervals and SBP time series. Six-minute time series of RR intervals, systolic and diastolic pressures were analysed. The bias and distribution of differences between FFT and SPWVD methods in RR intervals under base conditions were 1.4+/-0.4% (r2=0.94; P<0.01) in LF/LF+HF: 1.5+/-0.5% ( r2=0.92; P<0.01) in HF/LF+HF and 4.8+/-1.9% (r2=0.92; P<0.01) in LF/HF. In SBP the bias and distribution were 1.5+/-0.8% (r2=0.90) P<0.05) in LF/LF+HF and 1.7+/-0.6% (r2=-0.92; P<0.01) in HF/LF+HF. In the frequency domain analysis of RR intervals and SBP there was no difference between FFT and SPWVD. The agreement between the methods demonstrates that in stationary signals both methods can be used interchangeably. SPWVD may be an interesting tool to analyse biomedical signals; it provides a good resolution at high frequency and a good frequency resolution at low frequencies independently if signals remain stationary.

Adrenergic beta-Antagonists↗
PubMedDate not supplied

The prehospital use of nitroglycerin according to standing medical orders in an urban EMS system.

PURPOSE: The purposes of this study are to quantify the use of nitroglycerin (NTG) in prehospital care, to detect deviations from the Standing Medical Orders (SMO), to determine the effectiveness of its administration, and the incidence of clinically significant adverse reactions (hypotension, bradycardia). METHOD: Retrospective review of 7683 Advanced Life Support (ALS) telemetry, base-station contacts over a three month period (June, July, August 1990) to identify all prehospital patient contacts in which NTG was utilized. SETTING: The Resource Hospital/Telemetry Base-Station and two community hospitals/Telemetry Base-Stations for the Chicago North EMS System. RESULTS: There were 445 runs in which NTG was indicated as per SMO. Two hundred eighty-eight patients (64.7%) received NTG for appropriate indications as per SMO, 203 for ischemic chest pain (45.6%), 79 for pulmonary edema (17.7%), and six for both (1.3%). There were 157 (35.5%) runs in which NTG was indicated, but not administered. There were 22 patients who received NTG for indications that deviated from the SMO. Reassessment data concerning the subjective symptom was completed on 118 patients (40.9%), 92 (45.3%) patients with chest pain and 26 with dyspnea (32.9%). Following the administration of NTG, 21 patients (10.1%) with chest pain were unchanged, while 13 with dyspnea (15.3%) improved, 13 patients (15.3%) were unchanged, and none worsened. In 121 patients, the systolic blood pressure (SBP) decreased, while 24 were unchanged (5.4%), and 28 had an increase (6.3%). The mean initial value SBP was 176 +/- 44 mmHg and the repeat mean SBP was 164 +/- 41 mmHg with a mean decrease of 12 +/- 22 mmHg. The diastolic blood pressure (DBP) decreased in 87 patients, was unchanged in 53 (11.9%), and increased in 33 (7.4%). The initial mean DBP was 97 +/- 24 mmHg, the repeat mean DBP was 92 +/- 23 mmHg, a mean decrease of 5 +/- 15 mmHg. Only one patient became hypotensive with the administration of NTG and was successfully resuscitated with a fluid bolus of 300 ml normal saline. CONCLUSIONS: In this EMS system, NTG is under-utilized based on the indications delineated by this system's SMOs. Reassessment is documented infrequently, but when completed, clinically significant adverse reactions are rare. Since the incidence of hypotension and bradycardia are rare, the inability to establish an IV line should not preclude the administration of NTG.

Aged↗
PubMed2002

Theory and applications of biotelemetry.

In this study, biotelemetry and its evolution is explained in detail. Bioelectric and physiological variables could be measured by biotelemetry systems. The development of a biotelemetry system and its principal operation are presented. The components of a biotelemetry system are explained. Biomedical data has been telemetered through every medium between two sites by using a variety of modulated energy forms. Designing of the link between transmitter and receiver is described. Important factors in designing a backpack or implanted telemeter are explained. The main features of implanted biotelemetry units are determined. Single-channel and multichannel biotelemetry systems are defined. The types of telemetry, and a comparison thereof, are given. The power sources of biotelemetry systems and features of different power sources are explained. A survey of biotelemetry applications on humans and animals is presented and advantages of using biotelemetry systems are determined.

Animals↗
PubMed2003

Influence of shock training and explicit fear-conditioned cues on sleep architecture in mice: strain comparison.

Fear conditioning is thought to model anticipatory anxiety. Inbred mouse strains exhibit different levels of reactivity to aversive environmental stimuli, which may reflect anxiety. We examined the effects of fear conditioning on sleep in mouse strains that differ on behavioral measures of anxiety. Mice (BALB/cJ [C], C57BL/6J [B6], CB6F1/J [CB6], n = 7-10 per strain) were implanted with transmitters for recording sleep by telemetry. Baseline sleep was recorded, and the mice were trained to associate a cue (tone) with footshock (15 cue-shock pairings on 4 consecutive days). Sleep was recorded after shock training and again 4 to 5 days later after presentation of the cue alone. Shock training produced a relatively selective suppression of rapid eye movement sleep (REM) that was greater in the C strain compared to the B6 and CB6 mice. Post-training exposure to the cue alone suppressed REM in all strains. The C strain exhibited a relatively greater immediate suppression of REM, and the CB6 hybrid mice showed the greatest overall suppression of REM. These data demonstrate that stimuli associated with an aversive event can alter sleep and suppress REM in much the same way as exposure to the event itself. Fear conditioning may provide a model for examining genetic and neural mechanisms underlying the influence of anxiety on sleep.

Analysis of Variance↗
PubMed2001

[Long-term monitoring].

The electroencephalography (EEG) keeps its essential role in the differential diagnosis of epileptic and non-epileptic seizure disorders and in the classification of the different types of epilepsies and epileptic seizures, mainly due to its unique capability to directly show epileptic malfunction. The routine EEG usually records the EEG between seizures (interictal EEG) and remains a cost effective, highly specific, but not very sensitive method in epileptology. However, a diagnosis based on clinical data and routine EEG alone if often difficult and 20-30% of patients referred to an epilepsy centre due to medical refractory seizures do not have epilepsy. The different methods of long-term monitoring (cable and radio telemetry, ambulatory EEG monitoring) can continuously record EEG and other biosignals for many hours up to several days and allow a direct assessment of seizures (ictal EEG). In combination with the video-recorded symptomatology, these methods establish a precise diagnosis and follow-up of uncertain seizure disorders in the majority of cases. Although technical and personnel investment is relatively high the method used in expert hands is efficient, accepted and cost effective.

Diagnosis, Differential↗
PubMed2006

'Cardiogenic vertigo'--true vertigo as the presenting manifestation of primary cardiac disease.

BACKGROUND: A 90-year-old woman presented to a hospital emergency department with a brief loss of consciousness that was heralded by spinning vertigo lasting approximately 2 min. She had a long history of intermittent brief episodes of rotatory vertigo, presyncope, and non-vertiginous dizziness, occurring either with or without loss of consciousness. Although initially attributed to symptomatic carotid artery stenosis, these episodes persisted, despite surgical restoration of carotid artery blood flow 1 year after her first syncope. Her medical history was otherwise notable for hypertension, mild depression and a gradual decline in gait and balance function attributed to left hip arthritis and older age. INVESTIGATIONS: Bedside history and examination, non-contrast head CT scan, electrocardiogram, transthoracic echocardiogram, and bedside cardiac telemetry. DIAGNOSIS: Sick sinus syndrome or severe reflex bradycardia with asystole causing recurrent, episodic vertigo, presyncope, non-vertiginous dizziness and syncope (Stokes-Adams attacks). MANAGEMENT: Placement of a temporary pacing wire, followed by surgical implantation of a single-chamber ventricular (VVI) pacemaker.

Adams-Stokes Syndrome↗
PubMed2005

Mild to moderate hyperthermia does not worsen outcome after severe intracerebral hemorrhage in rats.

Hyperthermia worsens outcome in clinical and experimental studies of ischemic stroke. Thus, we tested whether hyperthermia aggravates intracerebral hemorrhage (ICH) in rats. A striatal hemorrhage was produced via an infusion of bacterial collagenase. In a preliminary experiment, we compared brain and core temperatures (via telemetry) during heating (infrared lamp). The brain temperature rise exceeded that produced by enforced core hyperthermia, which was used subsequently. In these experiments up to three hyperthermia conditions (versus normothermia) were tested including: hyperthermia (>38.5 degrees C) over the first (HYP-1) or second 24 h period (HYP-2) after ICH and 3 h of 40 degrees C hyperthermia starting 12 h after ICH (HYP-3). The HYP-1, HYP-2, and HYP-3 treatments did not affect functional deficits (e.g., spontaneous forelimb use, skilled reaching) or the volume of injury at 30 days. Furthermore, the HYP-1 treatment did not aggravate injury or deficits at 7 days. Bleeding and inflammation, which contribute to pathology, were not significantly altered by HYP-1 and HYP-3 treatments. Bleeding was assessed at 1 day, and macrophages and neutrophils were counted at 2 and 4 days. Accordingly, hyperthermia, under the present conditions, did not worsen outcome after striatal ICH.

Animals↗
PubMed2006

A simple method to induce focal brain hypothermia in rats.

Hypothermia reduces cell death and promotes recovery in models of cerebral ischemia, intracerebral hemorrhage and trauma. Clinical studies report significant benefit for treating cardiac arrest and studies are investigating hypothermia for stroke and related conditions. Both local (head) and generalized hypothermia have been used. However, selective brain cooling has fewer side effects than systemic cooling. In this study, we developed a method to induce local (hemispheric) brain hypothermia in rats. The method involves using a small metal coil implanted between the Temporalis muscle and adjacent skull. This coil is then cooled by flushing it with cold water. In our first experiment, we tested whether this method induces focal brain hypothermia in anesthetized rats. Brain temperature was assessed in the ipsilateral cortex and striatum, and contralateral striatum, while body temperature was kept normothermic. Focal, ipsilateral cooling was successfully produced, while the other locations remained normothermic. In the second experiment, we implanted the coil, and brain and body temperature telemetry probes. The coil was connected via overhead swivel to a cold-water source. Brain hypothermia was produced for 24 h, while body temperature remained normothermic. A third experiment measured brain and body temperature along with heart rate and blood pressure. Brain cooling was produced for 24 h without significant alterations in pressure, heart rate or body temperature. In summary, our simple method allows for focal brain hypothermia to be safely induced in anesthetized or conscious rats, and is, therefore, ideally suited to stroke and trauma studies.

Anesthesia↗
PubMed2005

Field test results of an automated exposure assessment tool, the local positioning system (LPS).

A user-friendly environmental monitoring system that collects real time data has been developed. Flash card memory logs exposure data from multiple sensors along with corresponding times and positions. Optional use of telemetry repeaters and a reference station allows central monitoring of data to assess exposure and to initiate intervention when safe levels are exceeded. A software analysis package allows researchers to identify exposure hot spots and direct control efforts, with the ultimate goal being to reduce injury and disease. Preliminary field test results document position accuracy and system performance in harsh environments.

Air Pollutants, Occupational↗
PubMed1999

Telemetric registration of heart rate and blood pressure in the same unrestrained goats during pregnancy, lactation and the non-pregnant, non-lactating period.

The purpose of this study was to investigate how changes in heart rate and arterial blood pressure relate to the time of day, reproductive period and feeding routines in dairy goats (Capra hircus). Registrations were made by radiotelemetry in the same four goats during pregnancy, lactation and the non-pregnant, non-lactating (dry) period. Heart rate rose around the morning and afternoon feedings, whereas blood pressure did not show any diurnal rhythm. Comparison between reproductive periods revealed that heart rate was higher during the fifth month of pregnancy than during lactation and the dry period, whereas for blood pressure no such differences between periods were found. Withholding three meals from lactating goats resulted in a continuous slowdown of the heart rate, whereas blood pressure fluctuated. Re-feeding temporarily increased the heart rate but had no effect on blood pressure which continued to fluctuate. After another 2 days, blood pressure (but not heart rate) had stabilized. Food-restriction, aimed at terminating milk production resulted in a consistently depressed heart rate and reduced the mean and systolic blood pressures at night. The results show that with this implantable telemetry device it is possible to measure both heart rate and blood pressure day and night in the same unrestrained animals over a length of time long enough to include all reproductive periods. Our results emphasize that when planning experiments it is important that the exact stage in each reproductive period, the act of feeding and the amount of food given be taken into account.

Animals↗
PubMed2000

Cardiac natriuretic peptides and continuously monitored atrial pressures during chronic rapid pacing in pigs.

Changes in atrial natriuretic peptide (ANP), N-terminal proatrial natriuretic peptide and brain natriuretic peptide (BNP) were evaluated in relation to continuously monitored atrial pressures in a pacing model of heart failure. Pigs were subjected to rapid atrial pacing (225 beats min-1) for 3 weeks with adjustments of pacing frequencies if the pigs showed overt signs of cardiac decompensation. Atrial pressures were monitored by a telemetry system with the animals unsedated and freely moving. Left atrial pressure responded stronger and more rapidly to the initiation of pacing and to alterations in the rate of pacing than right atrial pressure. Plasma natriuretic peptide levels were measured by radioimmunoassay and all increased during pacing with BNP exhibiting the largest relative increase (2.9-fold increase relative to sham pigs). Multiple regression analysis with dummy variables was used to evaluate the relative changes in natriuretic peptides and atrial pressures and the strongest correlation was found between BNP and left atrial pressure with R 2=0.81. Termination of pacing resulted in rapid normalization of ANP values in spite of persistent elevations in atrial pressures. This may reflect an increased metabolism or an attenuated secretory response of ANP to atrial stretch with established heart failure. In conclusion, 3 weeks of rapid pacing induced significant increases in atrial pressures and natriuretic peptide levels. All the natriuretic peptides correlated with atrial pressures with BNP appearing as a more sensitive marker of cardiac filling pressures than ANP and N-terminal proatrial natriuretic peptide.

Animals↗
PubMed2002

Telemedicine used for remote prehospital diagnosing in patients suspected of acute myocardial infarction.

INTRODUCTION: In patients with acute myocardial infarction (AMI), considerable time elapses from symptom onset until initiation of thrombolytic therapy or primary percutaneous coronary intervention. Prehospital diagnosing can reduce time delays, and remote diagnosing using telemedicine may be appropriate in areas and countries where ambulances are not staffed with physicians. OBJECTIVES: To evaluate whether it was technically feasible for physicians at a remote university hospital to diagnose ST-segment-elevation-AMI (AMI(STelev)) in patients suspected of AMI, who were transported by ambulances to a local hospital. To determine associated prehospital delays and in-hospital treatment delays. METHODS: Patients carried in telemetry equipped ambulances had 12-lead electrocardiograms (ECGs) acquired as soon as possible. En route to the local hospital the ECGs were transmitted to a remote university hospital, by use of the GSM-system. The physician on call at the university hospital interviewed the patients, who were provided with cellular phone headsets, and alerted the local hospital if signs of AMI(STelev), bundle-branch-block-AMI or malignant arrhythmia were detected. Patients transported by traditional ambulances were included in a prospective control group. RESULTS: In 214 (86%) of 250 patients prehospital diagnosing was successful. Geographically related transmission problems were the primary reason for failure. Ninety-eight per cent of transmitted electrocardiograms and obtained history takings were technically acceptable for diagnostic purposes. Door-to-needle times were shorter amongst patients with AMI(STelev) who were subjected to prehospital diagnosing (n = 13) as compared with patients transported by traditional ambulances (n = 14) (38 vs. 81 min) (P = 0.004). CONCLUSIONS: It was technically feasible to use telemedicine for remote prehospital diagnosing of patients suspected of AMI. Patients subjected to prehospital diagnosing had shorter door-to-needle times compared with a prospective control group.

Adult↗
PubMed2001

Telemetric monitoring of adrenocorticotrophin-induced hypertension in mice.

1. The mouse is the animal of choice for studies involving genetic manipulation and transgenic and knockout mice are valuable tools for physiological studies. We have studied adrenocorticotrophin (ACTH)- and steroid-induced hypertension in both rat and humans. The aim of the present study was to develop a model of ACTH-induced hypertension in the mouse and to assess a chronically implanted telemetric device for measurement of blood pressure (BP). 2. Male Swiss Outbred and Quackenbush Swiss (QS) mice (35-45 g) were implanted with TA11PA-C20 BP devices (Data Sciences International, St Paul, MN, USA) under isoflurane anaesthesia. Seven to 10 days later, mice were monitored telemetrically for baseline BP for 4 days. Mice were then randomly allocated to: (i) sham treatment with normal saline s.c.; or (ii) ACTH at 500 microg/kg per day, s.c. Mice were monitored 24 h/day for 10 days. 3. Sham treatment (n = 7) did not affect BP (114 +/- 2/84 +/- 1 to 115 +/- 2/84 +/- 1 mmHg; P = NS). Adrenocorticotrophin treatment (n = 5) raised BP from 112 +/- 7/82 +/- 4 to 138 +/- 3/104 +/- 4 mmHg, which was significantly different from sham treatment (P = 0.0021 for systolic BP; P < 0.0001 diastolic BP). The increase in BP with ACTH was comparable with that seen in previous studies in humans, sheep and rat. Sham and ACTH-treated animals each lost 3% bodyweight. 4. Administration of ACTH (500 microg/kg per day) raises BP in two strains of mice, measured using a telemetry system. This model will allow the selective use of transgenic and/or knockout mice to further elucidate the mechanism of ACTH- and steroid-induced hypertension.

Adrenocorticotropic Hormone↗
PubMed2003

Accumbal dopamine and serotonin in anticipation of the next aggressive episode in rats.

Autonomic and limbic neural activities are linked to aggressive behavior, and it is hypothesized that activities in the cardiovascular and monoaminergic systems play a role in preparing for an aggressive challenge. The objective was to learn about the emergence of monoamine activity in nucleus accumbens before an aggressive confrontation that was omitted at the regular time of occurrence, dissociating the motoric from the aminergic activity. Dopamine, serotonin, heart rate and behavioral activity were monitored before, during and after a single 10-min confrontation in resident male Long-Evans rats fitted with a microdialysis probe in the n. accumbens and with a telemetry sender (experiment 1). DA, but not 5-HT efflux, was confirmed to increase in n. accumbens during and after a single aggressive episode. In aggressive males that confronted an opponent daily for 10 days (experiment 2) heart rate rose 1 h before the regularly scheduled encounter relative to control rats, as measured on day 11 in the absence of any aggression. Concurrently, DA levels increased by 60-70% over baseline levels and 5-HT levels decreased by 30-35% compared to baseline levels. These changes were sustained over 1 h, and contrasted with no significant changes in DA, 5-HT, heart rate or behavioral activity in control rats. The rise in mesolimbic DA appears to be significant in anticipating the physiological and behavioral demands of an aggressive episode, and the fall in 5-HT in its termination, dissociated from the actual execution of the behavior.

Aggression↗
PubMed2001

Inability to communicate with ICDs: an underreported failure mode.

The inability to perform telemetry on an ICD may have many potential causes. We report three recently identified cases where such a finding was indicative of unexpected device failure. Two of these cases involved identical failure mechanisms resulting from arcing of current within the high voltage hybrid. This placed the device into a high current state that caused rapid and complete battery depletion. There were no company alerts issued regarding this systematic problem. A multicenter arrhythmia device/lead database would be extremely useful in providing timely and unbiased information concerning device problems.

Aged↗