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Cardiac Output
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| Cardiac output can be determined with PowerLab systems using several invasive and non-invasive methods.
Cardiac output (CO) is the quantity of blood that is pumped by the heart each minute. It is the product of stroke volume (the volume of blood ejected from the heart in a single beat) and heart rate. It may be determined using several invasive or non-invasive techniques in both animals and humans.
Invasive Methods
Thermodilution Technique
The thermodilution (TD) technique involves the injection of a cooled bolus solution into the right side of the heart and measuring the change in temperature within the circulation. The bolus is usually saline of a known volume and temperature. The resultant temperature change in the blood ejected from the heart is measured with a thermocouple placed in the aorta or carotid artery. A TD curve (temperature versus time) is recorded and CO determined by calculating the area under this curve.
The Cardiac Output Module (Windows only) is specifically designed software that automates the analysis of TD curves for the accurate determination of CO.
The module calculates: - cardiac output in mL/min
- baseline temperature
- area under the thermodilution curve
- baseline slope correction
The Cardiac Output Accessory Kit contains: - One Hamilton LR (Luer tip) Glass syringe (250µl)
- One PB600 Repeating Dispenser
- Six polyethylene catheters with needle hubs
- Four three-way taps
- Two Touhy Borst adaptors
For information on setting up and using the Cardiac Output Pod and Cardiac Output Accessory Kit download the CO Technique note.
Transit-Time Ultrasound Flow Meter
In contrast to traditional ultrasound techniques, transit-time ultrasound techniques incorporate two transmitters/sensors and a reflector plate that allows them to provide calibrated measurements of blood flow rate in milliliters per minute. Transit-time ultrasound technologies are not subject to problems with electrical interference or baseline drift and do not require direct contact with the vessel.
ADInstruments Transonic Flow Systems and Transonic cardiac output probes are available in various sizes for implanting in animals as small as mice through to adult pig aorta or pulmonary artery. These probes are available for both chronic and acute applications with the flow meters and are calibrated to provide the user with CO measurements in milliliters per minute. The flow meters easily integrate with any PowerLab data acquisition systems. For more information on probe selection or to discuss your particular application please contact your nearest ADInstruments representative.
Isolated Heart Preparations
Cardiac output can also be determined from Working Heart preparations in which the heart is dissected from the animal and perfused using specialized apparatus. Arterial flow can then be determined using ADInstruments Transonic Flow Systems and probe placed in or around the aorta.
ADInstruments supply complete Working Heart Systems for use with a variety of species from mice through to rabbits and include Radnoti Working Heart Apparatus, transducers, accessories and a PowerLab data acquisition system. For further information, download the Radnoti Isolated Perfused Heart Technique Note or contact your nearest ADInstruments' representative to discuss your particular application.
Non-Invasive Methods
Indirect Fick Method
This is a non-invasive method for the determination of CO that is based on the substitution of CO2 rather than O2 into the Fick equation as follows:
CO = VCO2 [ml/min]/(CO2art-CO2ven) [ml/L]
VCO2 Measurements
VCO2 (ml/min), is the rate of CO2 production by the body and is easily determined using a Exercise Physiology System or Gas Analyzer and Spirometer.
Arterial CO2 (CO2art )
Arterial CO2 may be estimated from expired PET CO2 measurements obtained using a Gas Analyzer and Spirometer or the Exercise Physiology System and the following equation:
PaCO2 = 5.5 + 0.90(PET CO2) - 0.0021(VT)
where PET CO2 is the end tidal PCO2 and VT is the tidal volume
(J.N. Myers, 1996, "Essentials of Cardiopulmonary Exercise Testing").
Arterial CO2 content (in ml/100ml of blood) can then be obtained by converting arterial PCO2 using the CO2 dissociation curve (J.N. Myers, 1996, "Essentials of Cardiopulmonary Exercise Testing").
Venous CO2 (CO2ven )
Whilst measurement of venous O2 content requires pulmonary artery catheterization, venous CO2 content can be measured non-invasively using rebreathing techniques. In general, the subject breathes into a bag that contains a high concentration of CO2 (9-14%). The high CO2 content of the rebreathing bag inhibits diffusion (and, therefore, removal of CO2 from the blood) and the subject's venous CO2 levels eventually equilibrate to the CO2 content of the rebreathing bag. It is this equilibrated CO2 tension that is used as an estimate of PCO2 in the venous blood, thereby completing the indirect Fick equation above.
CO2 content of a rebreathing bag may be measured using the Gas Analyzer connected to any PowerLab or using the measured continuously using the Exercise Physiology System.
GLP and 21 CFR Part 11
For those researchers working within a laboratory requiring GLP and 21 CFR Part 11 compliance the GLP Client and GLP Server are available for use with LabChart (Windows only) and PowerLab data acquisition systems. For more information, visit the Good Laboratory Practice application page or contact your nearest ADInstruments representative.
Other signals
In addition to a Cardiac Output signal, the PowerLab can record other cardiovascular parameters simultaneously. Visit the following web pages for more information: |
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| PowerLab (MacLab) citations: |
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| Protection of hearts from reperfusion injury by propofol is associated with inhibition of the mitochondrial permeability transition. |
| S.A. Javadov, K.H.H. Lim, P.M. Kerr, M.-Saadah Suleiman, G.D. Angelini, A.P. Halestrap, Cardiovascular Research, 45, 360-369, 2000. |
| Isolated rat hearts were prepared for working heart perfusion. During the experiment, heart function was assessed while in the working heart mode and data were collected at 5-min intervals for analysis. An inline flow meter allowed constant visualisation of aortic flow-rate (AF). Coronary flow-rate (CF) was obtained by timed collections of coronary effluent. Pressure transducers attached to the atrial feeding and aortic outflow lines were connected to ADInstruments Bridge Amp and a MacLab/4s which allowed for measurements of peak 'aortic' pressure (AP), left 'atrial' pressure (LAP) and pressure tracing derived heart rate (HR). Cardiac output (CO) was derived by adding aortic and coronary flow-rates. Rate-pressure product (RPP), expressed as mmHg.beats/ min was calculated (AP x HR). The external cardiac work (ECW), expressed as J/s, represents the product of cardiac output and peak aortic pressure (CO x AP). |
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| Reflex control of the cutaneous circulation duri(g passive body core heating in humans. |
| J.K. Peters, T. Nishiyasu, G.W. Mack, Journal of Applied Physiology, 88, 1756-1764, 2000. |
| The impact of body core heating on the interaction between the cutaneous and central circulation during blood pressure challenges was examined in eight adults. Subjects were exposed to -10 to -90 mmHg lower body negative pressure (LBNP) in thermoneutral conditions and -10 to -60 mmHg LBNP during heat stress. We measured forearm vascular conductance (FVC) by plethysmography; cutaneous vascular conductance (CVC) by laser-Doppler techniques; and central venous pressure, arterial blood pressure, and cardiac output by impedance cardiography. Data were recorded continuously with an eight-channel MacLab and averaged over 30 second periods. |
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The material on this page is provided in good faith and believed accurate at the time of writing. No responsibility will be taken, or liability accepted, for damages arising from the use of information herein. Readers are urged to check with respective manufacturers the accuracy of all product related information.
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