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Composite Hydrogels with Engineered Microdomains for Optical Glucose Sensing at Low Oxygen Conditions. BIOSENSORS-BASEL 2017; 7:bios7010008. [PMID: 28117762 PMCID: PMC5371781 DOI: 10.3390/bios7010008] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/13/2016] [Revised: 01/14/2017] [Accepted: 01/16/2017] [Indexed: 12/20/2022]
Abstract
There is a growing need for advanced tools that enable frequent monitoring of biomarkers for precision medicine. In this work, we present a composite hydrogel-based system providing real-time optical bioanalyte monitoring. The responsive material, alginate-in-alginate (AnA), is comprised of an alginate hydrogel with embedded bioactive, nanofilm-coated phosphorescent microdomains; palladium tetracarboxyphenylporphyrin serves as an optical indicator, glucose oxidase as a model enzyme, and layer-by-layer deposited polyelectrolyte multilayers (PEMs) as the diffusion barrier. Glutaraldehyde crosslinking of the nanofilms resulted in a dramatic reduction in glucose diffusion (179%) while oxygen transport was not significantly affected. The responses of the AnA hydrogels to step changes of glucose at both ambient and physiological oxygen levels were evaluated, revealing controlled tuning of sensitivity and dynamic range. Stability, assessed by alternately exposing the responsive AnA hydrogels to extremely high and zero glucose concentrations, resulted in no significant difference in the response over 20 cycles. These AnA hydrogels represent an attractive approach to biosensing based on biocompatible materials that may be used as minimally-invasive, implantable devices capable of optical interrogation. The model glucose-responsive composite material studied in this work will serve as a template that can be translated for sensing additional analytes (e.g., lactate, urea, pyruvate, cholesterol) and can be used for monitoring other chronic conditions.
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Koeners MP, Ow CPC, Russell DM, Evans RG, Malpas SC. Prolonged and Continuous Measurement of Kidney Oxygenation in Conscious Rats. Methods Mol Biol 2016; 1397:93-111. [PMID: 26676130 DOI: 10.1007/978-1-4939-3353-2_9] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
A relative deficiency in kidney oxygenation, i.e., renal hypoxia, may contribute to the initiation and progression of acute and chronic kidney disease. A critical barrier to investigate this is the lack of methods allowing measurement of the partial pressure of oxygen in kidney tissue for long periods in vivo. We have developed, validated, and tested a novel telemetric method that can do this. Here we provide details on the calibration, implantation, implementation for data recording, and reuse of this telemetry-based technology for measurement of medullary tissue oxygen tension in conscious, unrestrained rats. This technique provides an important additional tool for investigating the impact of renal hypoxia in biology and pathophysiology.
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Affiliation(s)
- Maarten P Koeners
- School of Physiology and Pharmacology, University of Bristol, Medical Sciences Building, University Walk, Bristol, BS8 1TD, UK.
- Department of Physiology, Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand.
- Department of Nephrology, University Medical Centre Utrecht, Utrecht, The Netherlands.
| | - Connie P C Ow
- Department of Physiology, Monash University, Melbourne, VIC, Australia
| | - David M Russell
- Department of Physiology, Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
- Millar Ltd, Auckland, New Zealand
| | - Roger G Evans
- Department of Physiology, Monash University, Melbourne, VIC, Australia
| | - Simon C Malpas
- Department of Physiology, Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
- Millar Ltd, Auckland, New Zealand
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Guild SJ, McBryde FD, Malpas SC. Recording of intracranial pressure in conscious rats via telemetry. J Appl Physiol (1985) 2015; 119:576-81. [DOI: 10.1152/japplphysiol.00165.2015] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2015] [Accepted: 07/06/2015] [Indexed: 11/22/2022] Open
Abstract
Although cerebral perfusion pressure (CPP) is known to be fundamental in the control of normal brain function, there have been no previous long-term measurements in animal models. The aim of this study was to explore the stability and viability of long-term recordings of intracranial pressure (ICP) in freely moving rats via a telemetry device. We also developed a repeatable surgical approach with a solid-state pressure sensor at the tip of the catheter placed under the dura and in combination with arterial pressure (AP) measurement to enable the calculation of CPP. Telemeters with dual pressure catheters were implanted in Wistar rats to measure ICP and AP. We found that the signals were stable throughout the 28-day recording period with an average ICP value of 6 ± 0.8 mmHg. Significant light-dark differences were found in AP (3.1 ± 2.7 mmHg, P = 0.02) and HR (58 ± 12 beats/min, P = 0.003), but not ICP (0.3 ± 0.2 mmHg, P >0.05) or CPP (2.6 ± 2.8 mmHg, P > 0.05). Use of kaolin to induce hydrocephalus in several rats demonstrates the ability to measure changes in ICP throughout disease progression, validating this new solution for chronic measurement of ICP, CPP, and AP in conscious rats.
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Affiliation(s)
| | | | - Simon C. Malpas
- Department of Physiology and
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand; and
- Millar Ltd, Auckland, New Zealand
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Clark TM, Malpas SC, McCormick D, Guild SJ, Budgett DM. New multimodal data obtained in-vivo from a single ultra-miniature transducer. Biomed Microdevices 2015; 17:72. [PMID: 26137880 DOI: 10.1007/s10544-015-9984-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Recent advances in multimodal sensing technology and sensor miniaturization technologies are paving the way for a new era in physiological measurement. Traditional approaches have integrated several transducers on a single silicon chip or packaged several sensing elements within a biocompatible catheter. Thermal and electrical cross-talk between sensors, time-lag between parallel measurements, lower yields associated with the increased complexity, and restrictions on the minimum size are challenges presented by these approaches. We present an alternative method which enables simultaneous measurement of temperature, pressure and heart rate to be obtained from a single ultra-miniature solid-state transducer. For the first time multimodal data were obtained from the sensor located within the abdominal aortas of five rats. The catheter-tip sensor interfaces with a fully implanted and inductively powered telemetry device capable of operating for the lifetime of the animal. Results of this study demonstrate good agreement between the core-temperature measurement from the catheter-tip sensor and the reference sensor with mean difference between the two sensors of 0.03 °C ± 0.02 °C (n = 5, 7 days). Real-time data obtained in the undisturbed rat, revealed fluctuations associated with the rest-activity cycle, in temperature, mean arterial pressure and heart rate. The stress response was shown to elicit an elevation in the core temperature of 1.5 °C. This was heralded by an elevation in mean arterial pressure of 35 mmHg and heart rate of 160 bpm. Obtaining multiple parameters from a single transducer goes a considerable way towards overcoming challenges of the prior art.
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Affiliation(s)
- Therese M Clark
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand,
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Xu Q, Hu D, Duan B, He J. A Fully Implantable Stimulator With Wireless Power and Data Transmission for Experimental Investigation of Epidural Spinal Cord Stimulation. IEEE Trans Neural Syst Rehabil Eng 2015; 23:683-92. [PMID: 25680207 DOI: 10.1109/tnsre.2015.2396574] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Epidural spinal cord stimulation (ESCS) combined with partial weight-bearing therapy (PWBT) has been shown to facilitate recovery of functional walking for individuals after spinal cord injury (SCI). The investigation of neural mechanisms of recovery from SCI under this treatment has been conducted broadly in rodent models, yet a suitable ESCS system is still unavailable. This paper describes a practical, programmable, and fully implantable stimulator for laboratory research on rats to explore fundamental neurophysiological principles for functional recovery after SCI. The ESCS system is composed of a personal digital assistant (PDA), an external controller, an implantable pulse generator (IPG), lead extension, and stimulating electrodes. The stimulation parameters can be programmed and adjusted through a graphical user interface on the PDA. The external controller is placed on the rat back and communicates with the PDA via radio-frequency (RF) telemetry. An RF carrier from the class-E power amplifier in the external controller provides both data and power for the IPG through an inductive link. The IPG is built around a microcontroller unit to generate voltage-regulated pulses delivered to the bipolar electrode for ESCS in rats. The encapsulated IPG measures 22 mm × 23 mm × 7 mm with a mass of ∼ 3.78 g. This fully implantable batteryless stimulator provided a simplified and efficient method to carry out chronic experiments in untethered animals for medical electro-neurological research.
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Stehlin E, Malpas SC, Budgett DM, Barrett CJ, McCormick D, Whalley G, Fu F, Beil M, Rigel DF, Guild SJ. Chronic measurement of left ventricular pressure in freely moving rats. J Appl Physiol (1985) 2013; 115:1672-82. [DOI: 10.1152/japplphysiol.00683.2013] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Measurements of left ventricular pressure (LVP) in conscious freely moving animals are uncommon, yet could offer considerable opportunity for understanding cardiovascular disease progression and treatment. The aim of this study was to develop surgical methods and validate the measurements of a new high-fidelity, solid-state pressure-sensor telemetry device for chronically measuring LVP and dP/d t in rats. The pressure-sensor catheter tip (2-Fr) was inserted into the left ventricular chamber through the apex of the heart, and the telemeter body was implanted in the abdomen. Data were measured up to 85 days after implant. The average daytime dP/d t max was 9,444 ± 363 mmHg/s, ranging from 7,870 to 10,558 mmHg/s ( n = 7). A circadian variation in dP/d t max and heart rate (HR) was observed with an average increase during the night phase in dP/d t max of 918 ± 84 mmHg/s, and in HR of 38 ± 3 bpm. The β-adrenergic-agonist isoproterenol, β1-adrenergic agonist dobutamine, Ca2+ channel blocker verapamil, and the calcium sensitizer levosimendan were administered throughout the implant period, inducing dose-dependent time course changes and absolute changes in dP/d t max of −6,000 to +13,000 mmHg/s. The surgical methods and new technologies demonstrated long-term stability, sensitivity to circadian variation, and the ability to measure large drug-induced changes, validating this new solution for chronic measurement of LVP in conscious rats.
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Affiliation(s)
- Ellyce Stehlin
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Simon C. Malpas
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
- Department of Physiology, University of Auckland, Auckland, New Zealand,
- Millar Inc, Auckland, New Zealand
| | - David M. Budgett
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
- Millar Inc, Auckland, New Zealand
| | - Carolyn J. Barrett
- Department of Physiology, University of Auckland, Auckland, New Zealand,
| | - Daniel McCormick
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
- Millar Inc, Auckland, New Zealand
| | - Gillian Whalley
- Faculty of Social and Health Sciences, Unitec, Auckland, New Zealand; and
| | - Fumin Fu
- Novartis Institutes for BioMedical Research, Novartis Pharmaceuticals Corporation, East Hanover, New Jersey
| | - Michael Beil
- Novartis Institutes for BioMedical Research, Novartis Pharmaceuticals Corporation, East Hanover, New Jersey
| | - Dean F. Rigel
- Novartis Institutes for BioMedical Research, Novartis Pharmaceuticals Corporation, East Hanover, New Jersey
| | - Sarah-Jane Guild
- Department of Physiology, University of Auckland, Auckland, New Zealand,
- Millar Inc, Auckland, New Zealand
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Koeners MP, Ow CPC, Russell DM, Abdelkader A, Eppel GA, Ludbrook J, Malpas SC, Evans RG. Telemetry-based oxygen sensor for continuous monitoring of kidney oxygenation in conscious rats. Am J Physiol Renal Physiol 2013; 304:F1471-80. [DOI: 10.1152/ajprenal.00662.2012] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
The precise roles of hypoxia in the initiation and progression of kidney disease remain unresolved. A major technical limitation has been the absence of methods allowing long-term measurement of kidney tissue oxygen tension (Po2) in unrestrained animals. We developed a telemetric method for the measurement of kidney tissue Po2 in unrestrained rats, using carbon paste electrodes (CPEs). After acute implantation in anesthetized rats, tissue Po2 measured by CPE-telemetry in the inner cortex and medulla was in close agreement with that provided by the “gold standard” Clark electrode. The CPE-telemetry system could detect small changes in renal tissue Po2 evoked by mild hypoxemia. In unanesthetized rats, CPE-telemetry provided stable measurements of medullary tissue Po2 over days 5− 19 after implantation. It also provided reproducible responses to systemic hypoxia and hyperoxia over this time period. There was little evidence of fibrosis or scarring after 3 wk of electrode implantation. However, because medullary Po2 measured by CPE-telemetry was greater than that documented from previous studies in anesthetized animals, this method is presently best suited for monitoring relative changes rather than absolute values. Nevertheless, this new technology provides, for the first time, the opportunity to examine the temporal relationships between tissue hypoxia and the progression of renal disease.
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Affiliation(s)
- Maarten P. Koeners
- Department of Physiology, Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
- Nephrology, University Medical Centre Utrecht, Utrecht, Netherlands
| | - Connie P. C. Ow
- Department of Physiology, Monash University, Melbourne, Australia
| | - David M. Russell
- Department of Physiology, Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
- Millar Instruments, Auckland, New Zealand; and
| | - Amany Abdelkader
- Department of Physiology, Monash University, Melbourne, Australia
| | | | - John Ludbrook
- Department of Surgery, University of Melbourne, Melbourne, Australia
| | - Simon C. Malpas
- Department of Physiology, Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
- Millar Instruments, Auckland, New Zealand; and
| | - Roger G. Evans
- Department of Physiology, Monash University, Melbourne, Australia
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Wang B, Hu AP, Budgett D. Power flow control based solely on slow feedback loop for heart pump applications. IEEE TRANSACTIONS ON BIOMEDICAL CIRCUITS AND SYSTEMS 2012; 6:279-286. [PMID: 23853149 DOI: 10.1109/tbcas.2011.2171689] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
This paper proposes a new control method for regulating power flow via transcutaneous energy transfer (TET) for implantable heart pumps. Previous work on power flow controller requires a fast feedback loop that needs additional switching devices and resonant capacitors to be added to the primary converter. The proposed power flow controller eliminates these additional components, and it relies solely on a slow feedback loop to directly drive the primary converter to meet the heart pump power demand and ensure zero voltage switching. A controlled change in switching frequency varies the resonant tank shorting period of a current-fed push-pull resonant converter, thus changing the magnitude of the primary resonant voltage, as well as the tuning between primary and secondary resonant tanks. The proposed controller has been implemented successfully using an analogue circuit and has reached an end-to-end power efficiency of 79.6% at 10 W with a switching frequency regulation range of 149.3 kHz to 182.2 kHz.
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Affiliation(s)
- Bob Wang
- Department of Electrical and Computer Engineering, The University of Auckland, Auckland 1142, New Zealand.
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Russell DM, McCormick D, Taberner AJ, Malpas SC, Budgett DM. A high bandwidth fully implantable mouse telemetry system for chronic ECG measurement. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2012; 2011:7666-9. [PMID: 22256114 DOI: 10.1109/iembs.2011.6091889] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
We report on the development of a novel system that enables the wireless transmission of high-bandwidth physiological data from a freely moving mouse. The system employs inductive power transfer (IPT) to continuously power a battery-less transmitter using an array of overlapping planar coils placed under the animal. This arrangement provides a minimum of 20 mW at all locations and orientations across the mouse cage by selecting a coil which will sufficiently power the transmitter. Coil selection is performed by feedback control across the 2.4 GHz wireless link. A device was constructed utilizing this novel IPT system and was used to capture high-fidelity electrocardiogram (ECG) signal sampled at 2 kHz in mice. Various attributes of the ECG signal such as QT, QRS, and PR intervals could be obtained with a high degree of accuracy. This system potentially provides lifetime continuous high bandwidth measurement of physiological signals from a fully implanted telemeter in a freely moving mouse.
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Affiliation(s)
- David M Russell
- Auckland Bioengineering Institute, University of Auckland, New Zealand.
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A fully implantable telemetry system for the chronic monitoring of brain tissue oxygen in freely moving rats. J Neurosci Methods 2012; 204:242-8. [DOI: 10.1016/j.jneumeth.2011.11.019] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2011] [Revised: 11/10/2011] [Accepted: 11/12/2011] [Indexed: 11/22/2022]
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Abstract
The ability to electrically stimulate neural and other excitable tissues in behaving experimental animals is invaluable for both the development of neural prostheses and basic neurological research. We developed a fully implantable neural stimulator that is able to deliver two channels of intra-cochlear electrical stimulation in the rat. It is powered via a novel omni-directional inductive link and includes an on-board microcontroller with integrated radio link, programmable current sources and switching circuitry to generate charge-balanced biphasic stimulation. We tested the implant in vivo and were able to elicit both neural and behavioural responses. The implants continued to function for up to five months in vivo. While targeted to cochlear stimulation, with appropriate electrode arrays the stimulator is well suited to stimulating other neurons within the peripheral or central nervous systems. Moreover, it includes significant on-board data acquisition and processing capabilities, which could potentially make it a useful platform for telemetry applications, where there is a need to chronically monitor physiological variables in unrestrained animals.
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Affiliation(s)
- DWJ Perry
- Bionics Institute, Victoria, Australia
- Department of Otolaryngology, The University of Melbourne, Victoria, Australia
| | - DB Grayden
- Bionics Institute, Victoria, Australia
- NeuroEngineering Laboratory, Department of Electrical and Electronic Engineering, The University of Melbourne, Victoria, Australia
| | - RK Shepherd
- Bionics Institute, Victoria, Australia
- Department of Otolaryngology, The University of Melbourne, Victoria, Australia
| | - JB Fallon
- Bionics Institute, Victoria, Australia
- Department of Otolaryngology, The University of Melbourne, Victoria, Australia
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Hu AP, Budgett D, Malpas SC, Dissanayake T. Efficient Power-Transfer Capability Analysis of the TET System Using the Equivalent Small Parameter Method. IEEE TRANSACTIONS ON BIOMEDICAL CIRCUITS AND SYSTEMS 2011; 5:272-282. [PMID: 23851478 DOI: 10.1109/tbcas.2010.2089685] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Transcutaneous energy transfer (TET) enables the transfer of power across the skin without direct electrical connection. It is a mechanism for powering implantable devices for the lifetime of a patient. For maximum power transfer, it is essential that TET systems be resonant on both the primary and secondary sides, which requires considerable design effort. Consequently, a strong need exists for an efficient method to aid the design process. This paper presents an analytical technique appropriate to analyze complex TET systems. The system's steady-state solution in closed form with sufficient accuracy is obtained by employing the proposed equivalent small parameter method. It is shown that power-transfer capability can be correctly predicted without tedious iterative simulations or practical measurements. Furthermore, for TET systems utilizing a current-fed push-pull soft switching resonant converter, it is found that the maximum energy transfer does not occur when the primary and secondary resonant tanks are "tuned" to the nominal resonant frequency. An optimal turning point exists, corresponding to the system's maximum power-transfer capability when optimal tuning capacitors are applied.
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de Jong W, Koolstra J, van Ruijven L, Korfage J, Langenbach G. A fully implantable telemetry system for the long-term measurement of habitual bone strain. J Biomech 2010; 43:587-91. [DOI: 10.1016/j.jbiomech.2009.09.036] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2009] [Revised: 09/23/2009] [Accepted: 09/27/2009] [Indexed: 10/20/2022]
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Current World Literature. Curr Opin Otolaryngol Head Neck Surg 2008; 16:490-5. [DOI: 10.1097/moo.0b013e3283130f63] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Guild SJ, Barrett CJ, McBryde FD, Van Vliet BN, Malpas SC. Sampling of cardiovascular data; how often and how much? Am J Physiol Regul Integr Comp Physiol 2008; 295:R510-5. [DOI: 10.1152/ajpregu.00139.2008] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Long-term measurement of cardiovascular variables by telemetry in laboratory animals has become indispensable in recent years. However, limited battery life and management of large volumes of recorded data are major drawbacks. These limitations can often be overcome by intermittent sampling of data. The question is, how much data does one need to collect to accurately reflect the underlying average value? To investigate this, 24-h continuous recordings of rabbit heart rate, arterial pressure, and integrated renal sympathetic nerve activity (RSNA) were resampled using a variety of protocols that differed with respect to the number of individual sampling periods used and the total amount of time that was sampled. The absolute percentage errors of estimates of the daily mean, standard deviation, and interquartile range were calculated for each sampling protocol. A similar analysis was repeated using arterial pressure data from rats. The results show that the number of sampling periods spread throughout the day had more effect than the total amount of data recorded. For example, just 2 h of total sampling time spread over 12 evenly spaced 10-min periods gave estimates of the daily mean of blood pressure and heart rate with < 1% error and RSNA with < 3% error. We show that accurate estimates of the daily mean of arterial pressure, heart rate, and RSNA can all be made using scheduled recording, and we recommend recording a minimum of 2 h/day spread over a number of periods throughout the day.
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