Integrated circuits for a bidirectional implantable pulsed Doppler ultrasonic blood flowmeter

Allen, Henry V.; Knutti, James W.; Meindl, J.D.

doi:10.1109/jssc.1978.1052060

Cited by 20 publications

(7 citation statements)

References 5 publications

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“…Of course, this poses a risk of missing interesting data. The selected timed-acquisition duration provided data for ϳ170 min per day, which is ϳ10 -50 times more in recordings relative to previous systems (1,2,13,22). Future improvements can include trigger-sampling periods by, for example, motion detectors or other types of external or even internal sensors.…”

Section: Discussionmentioning

confidence: 99%

A novel, fully implantable, multichannel biotelemetry system for measurement of blood flow, pressure, ECG, and temperature

Axelsson¹,

Dang²,

Pitsillides³

et al. 2007

Journal of Applied Physiology

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Axelsson M, Dang Q, Pitsillides K, Munns S, Hicks J, Kassab GS. A novel, fully implantable, multichannel biotelemetry system for measurement of blood flow, pressure, ECG, and temperature. J Appl Physiol 102: 1220 -1228, 2007. First published November 22, 2006; doi:10.1152/japplphysiol.00887.2006.-Biotelemetry provides highquality data in awake, free-ranging animals without the effects of anesthesia and surgery. Although many biological parameters can be measured using biotelemetry, simultaneous telemetric measurements of pressure and flow have not been available. The objective of this study was to evaluate simultaneous measurements of blood flow, pressure, ECG, and temperature in a fully implantable system. This novel system allows the measurement of up to four channels of blood flow, up to three channels of pressure, and a single channel each of ECG and temperature. The system includes a bidirectional radiofrequency link that allows the implant to send data and accept commands to perform various tasks. The system is controlled by a base station decoder/controller that decodes the data stream sent by the implant into analog signals. The system also converts the data into a digital data stream that can be sent via ethernet to a remote computer for storage and/or analysis. The system was chronically implanted in swine and alligators for up to 5 wk. Both bench and in vivo animal tests were performed to evaluate system performance. Results show that this biotelemetry system is capable of long-term accurate monitoring of simultaneous blood flow and pressure. The system allows, within the room, recordings, since the implant transmission range is between 6 and 10 m, and, with a relay, backpack transmission distance of up to 500 m can be achieved. This system will have significant utility in chronic models of cardiovascular physiology and pathology. chronic measurements; Doppler flow; telemetry; swine; alligator THE USE OF TELEMETRIC TECHNIQUES makes it possible to record and study physiological variables during long-term experiments with a minimum of disturbance to the animal. The absence of physical restraint and the ability to free range reduces stress and leads to more easily interpretable data. Fully implantable telemetric techniques also greatly reduce the risk of infection associated with leads and catheters protruding from the skin. In addition, telemetric techniques make it possible to study animals in their natural habitat (ecophysiology) and during social interactions and to correlate normal behaviors with physiological variables. It is clear that many interpretations of previous physiological data are hampered by stress induced from confinement or human interaction. This unwanted stress is greatly reduced by using a fully implantable telemetric system. The first successful transmission of biological information from a living animal was performed in 1869 by Marey (18). This was followed by Einthoven's experiment in 1903 in which he used a telephone line to transmit ECG data over a 1.5-km distance (9). If we ...

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Section: Discussionmentioning

confidence: 99%

A novel, fully implantable, multichannel biotelemetry system for measurement of blood flow, pressure, ECG, and temperature

Axelsson¹,

Dang²,

Pitsillides³

et al. 2007

Journal of Applied Physiology

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“…Several interesting systems have been described that use different flowmeter techniques, such as, electromagnetic flowmeters (Fryer et al, 1975), ultrasonic Doppler shift techniques (Cathignol et al, 1976;Allen et al, 1978Allen et al, , 1979 and interferometric ultrasonic techniques (Rader et al, 1975). However, most system, have parts of the devices externally mounted and are consequently limited for use in larger animals (Franklin et al, 1964;Yonezawa et al, 1989Yonezawa et al, , 1992Spelman et al, 1991;Kong et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

“…However, most system, have parts of the devices externally mounted and are consequently limited for use in larger animals (Franklin et al, 1964;Yonezawa et al, 1989Yonezawa et al, , 1992Spelman et al, 1991;Kong et al, 2007). Other problems with these devices are the high power consumption (Fryer et al, 1975;Cathignol et al, 1976;Allen et al, 1978Allen et al, , 1979 and the bulk flow probes (Rader et al, 1975).…”

Section: Introductionmentioning

confidence: 99%

A fully implantable multi-channel biotelemetry system for measurement of blood flow and temperature: a first evaluation in the green sturgeon

Gräns

Axelsson

Pitsillides³

et al. 2008

Hydrobiologia

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The objective of this study was to evaluate a novel fully implantable radio-based blood flow biotelemetry system which allows simultaneously measurement of blood flow on two channels and temperature on one channel, in fish. These are the first recordings of blood flow from free-swimming fish, showing that the system is capable of recording blood flow in the ventral aorta (cardiac output) and celiacomesenteric artery (gastrointestinal blood flow) in green sturgeon Acipenser medirostris exposed to a series of different stimuli for up to 7 days after implantation. The results showed stable base line recordings and blood flow was used to calculated heart rate (f H ) and stroke volume (V s ). It was possible to reproduce the same type of responses as has previously been reported during exposure to hypoxia, temperature, stress and feeding. The mass of our implant was less than 2% of the body mass which is well within the recommended sizes for surgically implanted telemetry transmitters and it fitted easily within the abdominal cavity of the sturgeon. A fully implantable system minimizes the risk of infection/expulsion and maximizes the likelihood that the studied fish will behave naturally and be treated normally by surrounding fish. The use of biotelemetry in basic comparative physiology and applied animal ecology could help scientists to collect information that has previously been challenging to obtain and to open the possibility for new types of physiological and ecophysiological studies.

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“…Three hemodynamic factors were evaluated in the study: Re, Womersley number (α) and Strouhal number (St). The Buckingham Pi theorem of dimensional analysis determines these three parameters to be the dimensionless numbers that define the phenomena of flow instabilities [13], [16], [19], [20], [33]. The Reynolds number (Re) is associated with the transition from laminar flow to turbulent flow in in vivo and in vitro studies [13], [14], [19], [34], and it also represents the effect of these dimensionless numbers on the presence of flow instabilities in in vitro studies.…”

Section: Hemodynamic Analysis Of Avs Stenosismentioning

confidence: 99%

Hemodynamic Quantitative Analysis Based on Doppler Ultrasound for Arteriovenous Shunt Stenosis Screening

Chen

Liu

et al. 2019

IEEE Access

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Clinically, arteriovenous shunt (AVS) stenosis results in turbulent and pulsatile flow because of high resistance and pressure within a narrowed space inside a stenotic access. Palpation and ultrasound methods are primarily used (first-line examination) to rapidly screen the risk of the degree of stenosis (DOS). Therefore, quantitative hemodynamic analysis involving Doppler ultrasound is performed in patients suffering from AVS stenosis and undergoing long-term hemodialysis. Doppler ultrasound with a center frequency of 7.5 MHz can provide substantial resolution and sensitivity to the measurement of blood flow velocity within a range of depth of 20.0-30.0 mm and a scan diameter of 10.0 mm. A hemodynamic method is used to analyze blood flow through a hemodialysis access in terms of dimensionless numbers. In this study, velocities were measured using Doppler ultrasound at three specific sites in vessels, namely, arterial anastomosis, loop, and venous anastomosis sites. Dimensionless numbers, such as supracritical Reynolds numbers, critical peak Reynolds numbers, and resistive indices, are determined in accordance with parallel conditional expressionbased rules to create decision trees for the rapid screening of the DOS at the abovementioned specific sites. For the enrolled subjects, results demonstrate that noninvasive hemodynamic analysis with Doppler ultrasound measurements and parallel decision trees has potential for the efficient screening of the DOS in patients suffering from AVS stenosis and undergoing long-term hemodialysis. Experimental results also indicate that the hit and true-positive rates of the proposed screening method in clinical indication are higher than those of the machine learning method.INDEX TERMS Doppler ultrasound, quantitative hemodynamic analysis, supracritical Reynolds number, resistive index, degree of stenosis.

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Integrated circuits for a bidirectional implantable pulsed Doppler ultrasonic blood flowmeter

Cited by 20 publications

References 5 publications

A novel, fully implantable, multichannel biotelemetry system for measurement of blood flow, pressure, ECG, and temperature

A novel, fully implantable, multichannel biotelemetry system for measurement of blood flow, pressure, ECG, and temperature

A fully implantable multi-channel biotelemetry system for measurement of blood flow and temperature: a first evaluation in the green sturgeon

Hemodynamic Quantitative Analysis Based on Doppler Ultrasound for Arteriovenous Shunt Stenosis Screening

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