SEARCH · PubMed Health

Results for “Telemetry”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,297 records · Page 72Linked to original sources

PubMed2005

Preliminary evaluation of implantable MOSFET radiation dosimeters.

In this paper, we report on measurements performed on a new prototype implantable radiation detector that uses metal-oxide semiconductor field effect transistors (MOSFETs) designed for in vivo dosimetry. The dosimeters, which are encapsulated in hermetically sealed glass cylinders, are used in an unbiased mode during irradiation, unlike other MOSFET detectors previously used in radiotherapy applications. They are powered by radio frequency telemetry for dose measurements, obviating the need for a power supply within each capsule. We have studied the dosimetric characteristics of these MOSFET detectors in vitro under irradiation from a 60Co source. The detectors show a dose reproducibility generally within 5% or better, with the main sources of error being temperature fluctuations occurring between the pre- and post-irradiation measurements as well as detector orientation. A better temperature-controlled environment leads to a reproducibility within 2%. Our preliminary in vitro results show clearly that true non-invasive in vivo dosimetry measurements are feasible and can be performed remotely using telemetric technology.

Calibration↗

PubMed1983

Non-invasive fetal monitoring using radiotelemetry.

A telemetry system for non-invasive monitoring of fetal heart rate and uterine contractions is described. Fetal heart information is obtained by means of Doppler ultrasound, and contractions information using an external tocodynamometer. The more important features of the device are described in detail; the full design is available from the authors. Typical recordings are presented, and the fetal heart rate traces are compared qualitatively with those obtained by direct ECG measurement, with the patient in bed, sitting and walking. The device is now in clinical use.

Electrocardiography↗

PubMed2004

The effect of local subcutaneous delivery of vascular endothelial growth factor on the function of a chronically implanted amperometric glucose sensor.

The foreign body capsule that forms around implanted devices such as glucose sensors is hypovascular and has limited permeability to glucose. Such a capsule may function better if well vascularized. We hypothesized that capsular vascularization achieved by local release of vascular endothelial growth factor (VEGF) would lead to enhanced function. Amperometric glucose sensor array disks, each with four indicating electrodes, were implanted into rats. Animals received local subcutaneous infusions of VEGF(165) via osmotic pumps at a location on the sensor face 2 mm from one of the electrodes ("near units"). "Intermediate" electrode units were 15 mm, and "distant" units were 22 mm, from the VEGF source. Every 2 weeks, a glucose infusion was given to assess sensor function by telemetry. Near units demonstrated a lower lag duration (delay after blood glucose) than intermediate and distant units. The mean absolute relative difference for near units was less than for distant units. The percentage of data pairs in the A region of the Clarke error grid of the near sensing units was greater than that of the distant units. Values for the functional measures for saline controls fell between near and distant VEGF values. Glucose sensor function was found to be more favorable in units immediately adjacent to the VEGF infusion port. The most likely cause for this finding is increased neovessel growth in the surrounding foreign body capsule. Slow release of angiogenic growth factors may be a potential method for chronically enhancing the function of a subcutaneously implanted biosensor.

Animals↗

PubMed1993

In-hospital experience with multiprogrammable implantable antitachycardia/antifibrillation devices.

Multiprogrammable, automatic internal defibrillators with (n = 45) and without (n = 15) antitachycardia pacing features were implanted in 60 consecutive patients with refractory, malignant ventricular tachycardia (VT) (n = 42) or fibrillation (VF) (n = 18). Left ventricular (LV) ejection fraction was reduced to 39% +/- 12% as a result of structural heart disease in 56 patients. The complexity of the systems caused no additional risks to the surgical procedure or postoperative management. VT/VF detection parameters were individually adjusted to the arrhythmia type (detection cycle length 323 +/- 40 ms in patients with VF vs 405 +/- 40 ms for VT patients, P < 0.05) and incidence (longer detection periods if frequent nonsustained VT was also present). Shock energy was reduced in patients with VT as compared to VF (11J vs 24J, P < 0.05). Antitachycardia pacing was activated in 19/28 (68%) patients with well tolerated VT. Signal, telemetry, as detected by the device, combined with programmability allowed the device to be checked for correct decisions (these were inappropriate in four patients in three of whom corrections were non-invasive) prior to discharge. In conclusion, in the automatic tachyarrhythmia control devices we studied, programmability and flexibility appeared to be clinically safe and useful. Prolonged observation periods are required, however, to evaluate the true clinical safety and persistent efficacy of device programmability and flexibility.

Algorithms↗

PubMed2003

Influence of contextual fear on sleep in mice: a strain comparison.

STUDY OBJECTIVES: This study assessed the influence of contextual fear on sleep in inbred and hybrid mouse strains. DESIGN: Uninterrupted baseline recordings of sleep were obtained for 3 days in 3 mouse strains. After baseline sleep recording sessions, fear-conditioned mice were presented 15 shock presentations on 4 consecutive days. Control mice were subjected to the same procedures except that they never received shock. Sleep was examined after shock training and after exposure to the shock context alone. SETTINGS: N/A. PARTICIPANTS: The subjects were mice of 2 inbred (C57BL/6J [B6], N=15; BALB/cJ [C], N=19) strains and 1 hybrid (CB6F1/J [CB6: C x B6], N=17) strain. INTERVENTIONS: Electroencephalograms (EEG) and activity were recorded by telemetry, and behavioral states were visually scored based on EEG and motor activity records. MEASUREMENTS AND RESULTS: Shock training selectively reduced rapid eye movement (REM) sleep in mice compared to time-matched baseline recordings. The reduction of REM sleep was significantly greater in the reactive C and the F1 hybrid strain compared to the less reactive B6 strain. Posttraining exposure to the context alone reduced REM sleep in much the same manner as exposure to the footshock, with the CB6 hybrid mice exhibiting greater alterations in sleep and a greater reduction of REM sleep. In contrast, mice that did not receive shock training showed increased REM sleep after being returned to the chamber. CONCLUSION: Aversive events and the fearful contexts that become associated with them can alter sleep in much the same way. Sleep disruptions after an aversive event or its reminders vary with genetic background.

Animals↗

PubMed2001

Atrial fibrillation after coronary artery bypass graft surgery is unrelated to cardiac abnormalities detected by transesophageal echocardiography.

UNLABELLED: Atrial fibrillation is a common complication of coronary artery bypass graft (CABG) surgery that is associated with adverse patient outcomes. We evaluated whether preexisting abnormalities of cardiac structure or function detected with transesophageal echocardiography (TEE) are prevalent in patients later developing atrial fibrillation after CABG surgery. TEE imaging was performed after induction of general anesthesia, but before primary CABG surgery, in 62 consecutive patients without cardiac valvular disease or preexisting atrial fibrillation. Measurements included left atrial diameter, left ventricular wall thickness, left ventricular end-systolic and end-diastolic dimensions and fractional area change. Pulsed-wave Doppler measurements of pulmonary venous and trans-mitral blood flow velocity were obtained. Continuous monitoring with telemetry electrocardiography for the development of atrial fibrillation was performed. Eighteen patients (29%) developed postoperative atrial fibrillation. There were no significant differences in left atrial or left ventricular TEE variables or pulsed-wave Doppler pulmonary venous flow measurements between patients with and without postoperative atrial fibrillation. After adjusting for age and duration of aortic cross-clamping, there were no differences in the transmitral Doppler diastolic filling variables between these same groups. These data suggest that atrial fibrillation commonly occurs after CABG surgery in the absence of atrial enlargement or Doppler-derived cardiac functional abnormalities. The data imply that the use of TEE immediately before surgery would be an insensitive means for routine identification of patients susceptible to this arrhythmia. IMPLICATIONS: Transesophageal echocardiography performed immediately before coronary artery bypass graft (CABG) surgery is not useful for prediction of susceptibility to develop atrial fibrillation postoperatively. Postoperative atrial fibrillation commonly occurs after CABG surgery in the absence of preoperative atrial enlargement or Doppler derived functional abnormalities.

Aged↗

PubMed1994

Effect of bombesin on core temperature in rats: studies involving radiotelemetry.

The effect of centrally administered bombesin on core temperature was investigated in rats which had been chronically fitted with a cannula in the third cerebral ventricle and with an intraperitoneal temperature-monitoring radiotransmitter. Intracerebroventricularly administered bombesin (0.01, 0.1 or 1 microgram) resulted in hypothermia, the duration and depth of the effect being a function of the dose. The use of telemetry minimized experimental interventions in this study; the results demonstrate that the hypothermic response to bombesin is not dependent upon exposure to a low ambient temperature, food restriction or insulin treatment as suggested by previous studies involving measurement of core temperature by a rectal probe.

Animals↗

PubMedDate not supplied

Partnering with patients and families in designing visual cues to prevent falls in hospitalized elders.

Prevention of falls in hospitalized elderly is critical to avoid injury and maintain independence. As part of a comprehensive program, nursing staff in a medical telemetry unit partnered with patients and their families to design and implement an educational poster to prevent falls. Ongoing patient/family feedback was used to modify the poster until it was appealing and effective for patients. The effort resulted in a marked decrease in falls on the unit over the pilot period.

Accident Prevention↗

PubMed1989

A four-year program to train residents in emergency medical services.

There is general agreement that residents in the field of emergency medicine require extensive training in emergency medical services (EMS). This paper outlines a comprehensive four-year training program in EMS that has been integrated into the emergency medicine residency curriculum of the University of Cincinnati since 1985. The EMS program is comprehensive and makes it possible for the level and type of EMS activities that are provided to match the evolving expertise of the resident. The program provides a significant amount of practical training in ground and aeromedical transport, in disaster work, in telemetry communications, and in other areas. Evaluation of the program is at an early stage but informal reports are strongly positive.

Curriculum↗

PubMedDate not supplied

Steady state hemodynamic and energetic characterization of the Penn State/3M Health Care Total Artificial Heart.

Total Artificial Heart (TAH) development at Penn State University and 3M Health Care has progressed from design improvements and manufacturing documentation to in vitro and in vivo testing to characterize the system's hemodynamic response and energetic performance. The TAH system is completely implantable and intended for use as an alternative to transplantation. It includes a dual pusher plate pump and rollerscrew actuator, welded electronics and battery assembly, transcutaneous energy transmission system, telemetry, and a compliance chamber. In vitro testing was conducted on a Penn State mock circulatory loop with glycerol/water solution at body temperature. Tests were performed to characterize the preload and afterload response, left atrial pressure control, and power consumption. A sensitive preload response was demonstrated with left atrial pressure safely maintained at less than 15 mm Hg for flow rates up to 7.5 L/min. Variations in aortic pressure and pulmonary vascular resistance were found to have minimal effects on the preload sensitivity and left atrial pressure control. In vivo testing of the completely implanted system in its final configuration was carried out in two acute studies using implanted temperature sensors mounted on the electronics, motor, and energy transmission coil in contact with adjacent tissue. The mean temperature at the device-tissue interface was less than 4 degrees C above core temperature.

Animals↗

PubMedDate not supplied

Assessment of chronically implanted subcutaneous glucose sensors in dogs: the effect of surrounding fluid masses.

We developed a continuous, distributed-anode glucose sensor and now report on its use during subcutaneous implantation in dogs without diabetes. Using telemetry, we monitored sensor response to weekly administration of intravenous glucose. In a preliminary attempt to reduce fibrosis around the sensor, some sensors were designed to slowly release dexamethasone (DEX). Before implantation, in vitro sensor sensitivity was similar to values obtained after explantation (0.66 +/- 0.09 vs 1.07 +/- 0.19 nA/mM, n = 9, p = ns). Sensitivity in individual animals varied substantially over time. Average longevity of sensors was 32.1 +/- 8.6 days. Device failure was caused by leakage of fluid into, or interruption of, circuitry. Lag time during glucose ascent averaged 5.8 +/- 1.0 min. In devices that became surrounded by fluid masses, lag time during descent was greater than in devices without fluid (33.7 +/- 4.5 vs 10.7 +/- 1.6 min, p < 0.001). There was a nonsignificant tendency for longevity of the six sensors that contained DEX to be greater than the eight sensors without DEX (47.2 +/- 18.7 vs 20.8 +/- 3.6 days, p = ns). The development of fluid masses surrounding electrochemical glucose sensors prolongs lag time and probably contributes to the commonly observed instability of sensitivity over time. In future long-term implant studies, it is likely that avoidance of fluid masses will improve sensor function.

Animals↗

PubMed2000

An international survey of long-term video/EEG services.

To determine current practices in the provision of video-EEG services, the authors conducted an international survey by post. The aim of the survey was to evaluate, by reference to other centres, how and why certain things are done, be assured that their own center is providing a quality service, identify weaknesses in their service, and from this, set improvement goals and objectives. A purposive sampling method was used by sending questionnaires to 78 hospitals where it was believed a long-term video-EEG monitoring service existed. Completed survey questionnaires were returned from 42 centers. Although the survey mechanism may have resulted in self-selection bias, evaluation of the responses provides information on patient management, staffing levels, equipment, and equipment management. Ultimately, these data may aid in identifying a minimum set of requirements for the provision of a video-EEG telemetry service.

Americas↗

PubMed2000

Cardiac hypertrophy depends upon sleep blood pressure: a study in rats.

OBJECTIVE: The objective of this study was to determine whether cardiac hypertrophy in hypertensive rats could be reduced and normalized by intermittent reduction of blood pressure, and to determine whether left ventricular hypertrophy was related to 24 h workload or peak blood pressure responses. METHODS: Hypertension was created by the application of a 0.20 mm clip to the left renal artery. Blood pressure response was monitored using a telemetry system (Data Science International). Blood pressure was reduced for varying periods of the day by giving different doses of captopril in the drinking water or by intra-peritoneal administration. Cardiac size was measured by weighing the ventricles and factoring by the body weight to obtain a cardiac index. RESULTS: Captopril 75 mg/kg per day and 25 mg/kg per day in the drinking water administered between 1800 and 2000 h lowered the 24 h blood pressure more than captopril 15 mg/kg per day or 5 mg/kg per day intra-peritoneally given at 0800 h. Captopril 75 mg/kg per day and captopril 15 mg/kg per day (intra-peritoneal) caused regression of cardiac hypertrophy whereas the other doses had no effect The best predictor of the cardiac hypertrophy response was the blood pressure between 0800 and 1200 h (i.e. the sleeping blood pressure). Twenty-four hour cardiac work did not correlate with the response. CONCLUSION: Cardiac hypertrophy can be reduced by intermittent treatment of elevated blood pressure. It is also caused by intermittent elevation of blood pressure. It appears that the crucial factor is when these alterations in blood pressure take place. An elevated blood pressure during the sleeping hours causes left ventricular hypertrophy, whereas a normal blood pressure during the sleeping hours allows reduction. It is suggested that acute wall stress is the signal to initiate the events that lead to cardiac hypertrophy but this only occurs if the hormonal milieu is appropriate.

Animals↗

PubMed2004

Contrasting circadian rhythms of blood pressure among inbred rat strains: recognition of dipper and non-dipper patterns.

OBJECTIVE: The non-dipper pattern, i.e. the lack of nocturnal blood pressure (BP) fall, carries a high risk of cardiovascular complications, both in hypertensive and normotensive subjects. Without genetic engineering, experimental demonstration of the non-dipper phenomenon is lacking. The purpose of this study was to assess the haemodynamic and behavioural daily parameters among various strains of rats - spontaneously hypertensive rats (SHR), Wistar-Kyoto (WKY) and Fischer 344 (F344) - in order to characterize their circadian patterns and to detect a non-dipper animal model. METHODS: Changes in BP, heart rate (HR), and spontaneous locomotor activity (SLA) were recorded continuously for 11 days using telemetry in freely moving 10-week-old male SHR, WKY and F344 rats, in standardized laboratory conditions. Variations in haemodynamic and behavioural parameters were assessed in terms of day/night differences and spectral power corresponding with the 24-h period. RESULTS: All rats exhibited clear circadian variations in HR and in SLA, in synchrony with the light cycle. Light/dark differences in BP were significantly lower in F344 compared with those of SHR and WKY. The smaller circadian changes in BP observed in F344 were also demonstrated using spectral analysis: the peak detected at 24-h was reduced in F344 compared with SHR and WKY. CONCLUSION: The inbred F344 strain lacks the typical circadian BP rhythm while oscillations of HR and SLA are maintained, suggesting different regulatory mechanisms. The F344 strain may represent a useful animal model for studying the effects of drugs aimed at restoring the dipper status.

Animals↗

PubMed2004

Non-symmetrical double-logistic analysis of 24-h blood pressure recordings in normotensive and hypertensive rats.

OBJECTIVE: To determine the suitability of a new logistic curve fitting procedure to measure the diurnal rates of transition from the active to the asleep periods separately. METHOD: We applied this method to 24-h telemetry recordings of systolic, mean, diastolic arterial pressure (SAP, MAP, DAP, respectively), heart rate (HR) and locomotor activity of normotensive Sprague-Dawley rats (SDR) and spontaneously hypertensive rats (SHR). RESULTS: There was a similar pattern of higher awake and lower sleep values (16 +/- 1 mmHg SAP, 77 +/- 2 bpm HR and 40 +/- 2 units activity) in SHR. In SDR, awake-asleep differences were less for SAP (9 +/- 1 mmHg) but similar for HR (83 +/- 2 bpm). In SHR, while the blood pressure patterns were symmetrical, the rate of rise in activity and HR during arousal was more rapid than the rate of decline during the dark to light transition. By contrast in SDR, the arousal rate of increase in blood pressure and HR was much less than the rate of decline. Thus SHR have an exaggerated arousal surge in DAP compared with SDR. Double logistic provides a better fit than Cosinor or square wave and better estimates of day-night differences than partial Fourier. CONCLUSIONS: Analysis of 24-h recordings by a new logistic curve method reveals distinct asymmetric circadian patterns of cardiovascular and activity changes in rats. The greater surge in arousal blood pressure in SHR is not associated with differences in HR or activity changes and may be inherent to the underlying mechanisms contributing to the hypertension in SHR.

Animals↗

PubMed2004

Mechanisms underlying the sympathomimetic cardiovascular responses elicited by gamma-hydroxybutyrate.

Gamma-hydroxybutyrate (GHB) is generally thought to be a central nervous system depressant; however, GHB also has sympathomimetic cardiovascular actions. Radio telemetry was used to record the cardiovascular responses elicited by GHB (180-1000 mg/kg IV) in conscious rats. GHB elicited increases in mean arterial pressure (MAP) (24 +/- 3 to 60 +/- 5 mm Hg) lasting from 28 +/- 8 to 227 +/- 37 minutes. GHB (560 and 1000 mg/kg IV) also elicited a prolonged tachycardic response (85 +/- 23 and 95 +/- 22 bpm). The hypertension and tachycardia elicited by GHB (560 mg/kg) were reversed by the intravenous and intracerebroventricular administration of the GABAb receptor antagonist CGP 35348. CGP 35348 also reversed GHB-mediated increases in renal sympathetic nerve activity (RSNA). Administration of the purported GHB receptor antagonist NCS-382 reversed the increase in heart rate but not the pressor response elicited by GHB in telemetered rats. These data indicate that the intravenous administration of GHB markedly increases MAP, heart rate, and RSNA in conscious rats via activation of central GABAb receptors. In addition, GHB receptors appear to selectively mediate the increase in heart rate elicited by large doses of GHB.

Anesthetics, Intravenous↗

PubMed2000

Effect of push frequency on the economy of wheelchair racers.

PURPOSE: The aim of the study was to examine the effect of varying push frequency on pushing economy (oxygen uptake at a given speed). METHODS: Eight male wheelchair racers completed a series of exercise bouts on a wheelchair ergometer (Bromking Turbo Trainer, Bromakin, UK) at 6.58 m x s(-1). Initially, subjects self-selected their freely chosen push frequency (FCF); this was followed by 4 random trials pushing at 60, 80, 120, and 140% of this FCF. Steady state VO2 was determined using Douglas bags, and heart rate was recorded by telemetry. After each condition, a small capillary blood sample was obtained and analyzed for blood lactate concentration (BLa) and a rating of perceived exertion (RPE) was recorded. RESULTS: At 6.58 m x s(-1) oxygen uptake, RPE, and gross mechanical efficiency were nonlinearly related to push frequency. Analysis of variance showed a significant effect (P < 0.05) of cycle frequency on VO2. VO2 was 11% higher at the 140% FCF compared with the 100% FCF condition. Changes in push frequency had little effect on HR although BLa increased linearly and was higher at the 140% FCF condition compared with 60% FCF (P < 0.05). A two-dimensional sagittal plane video analysis showed large interindividual differences in propulsion style. Both cycle time and the propulsion phase (%) decreased as the push frequency increased. The start angle and end angle of hand contact were similar for conditions, whereas the range of trunk motion decreased with push frequency (P < 0.05). CONCLUSION: The results of this study showed that the push frequency had an effect on pushing economy, and that the athletes' FCF was the most economical.

Adolescent↗

PubMed2002

An implantable strain measurement system designed to detect spine fusion: preliminary results from a biomechanical in vivo study.

STUDY DESIGN: The strain distribution on the thoracic vertebrae during anteroposterior bending and torsion was examined for use with an implantable strain gauge system and miniature radio transmitter, which also were evaluated. OBJECTIVES: To identify strain gauge placement sites by testing cadaver spines in vivo, and to evaluate an implantable gauge bonding technique and subminiature radio transmitter for accurate strain monitoring. SUMMARY OF BACKGROUND DATA: Fusion is determined currently through the use of radiographic techniques. Discrepancies exist between radiographic evidence and more direct measurements of fusion such as operative exploration4,5,12 and biomechanical or histologic measurements.12,15 To facilitate the return of patients to full unrestricted activity, it would be useful to develop a technique for accurate in vivo determination of fusion. METHODS: Three cadaver spines were tested during anteroposterior bending and torsional loading in the control, instrumented, and instrumented plus polymethylmethacrylate states. The spines were instrumented with an ISOLA(R) (Acromed Corporation, Cleveland, Ohio) construct, and a simulated fusion was achieved through the application of polymethylmethacrylate. Strain gauges were attached in uniaxial, biaxial, and rosette configurations. The principal strains were calculated. Calcium phosphate ceramic-coated gauges were implanted in patients and recovered after up to 15 months in vivo. A radio transmitter was developed and tested for use in patients. RESULTS: The largest and most consistent strain changes after simulated fusion were recorded during torsional loading on the laminae of a vertebra directly underneath a hook. Calcium phosphate ceramic-coated strain gauges showed excellent bone bonding to the lamina when fusion occurred. Radio telemetry accurately tracked strain magnitudes and strain rates expected in patients. CONCLUSIONS: The consistency obtained in torsional loading indicates that this type of loading will provide the most useful data from patients in vivo. Excellent bonebonding and accurate strain transmission using a long-term strain measurement system and miniature radio transmitter indicate that strains collected from patients with this system will be accurate.

Adult↗