Blood flow is the quantity of blood that passes through the arterial or venous circulation within a period of time and is often expressed in milliliters or liters per minute. It may be measured either invasively or non-invasively and quantitatively or qualitatively. Blood flow can be easily recorded with PowerLab data acquisition systems. In these systems, blood flow meters interface and provide an analog output voltage (maximum ± 10 V) to the PowerLab data acquisition unit.
Non-Invasive Techniques Laser DopplerLaser Doppler systems use a fiber optic probe to apply light to a small area of tissue. The light is scattered by the tissue and a small amount of this light re-enters the optic fiber for recording. The direction and rate of blood flow in the capillaries cause a Doppler shift in the returned light, and it is this shift that constitutes the signal and used to determine blood flow.
Blood flow measurements using the Laser Doppler Blood FlowMeterThe absolute strength of the signal is related to several factors including the degree of vascularization of the tissue. Therefore, the signal strength can vary markedly with position of the laser tip and the tissue type. The signal is often referred to as 'tissue perfusion' rather than blood flow, as it cannot be directly calibrated in units, such a mL/min. Relative changes in the signal can be related to effects such as local vasodilatation/constriction and so this method is useful for some pharmacological studies where more invasive methods are not suitable.
Strain Gauge PlethysmographyThis non-invasive method is particularly suitable for human use. Venous occlusion plethysmography involves tying a strain gauge – in this case a stretchable tube containing a liquid metal, such as mercury or an indium-gallium alloy – around the limb. Changes in limb circumference alter the cross-sectional area of the tube and hence the electrical resistance of the liquid metal. This is monitored by a suitable meter, which can output an analog voltage signal direct to a PowerLab system. Suitable strain gauges and meters, as well as cuffs and inflators, such as the Hokanson EC6 meter which is suitable for use with PowerLab data acquisition systems.
Invasive Techniques ThermodilutionFor periodic determination of flow rates, the thermodilution method uses a small temperature probe to monitor the change in blood temperature when a bolus of cool fluid (of known volume and temperature) is injected into the circulatory system. The area under the curve produced when temperature is plotted against time is used to calculate blood flow and cardiac output. The Cardiac Output Pod is suitable for use ONLY with animals and uses T-type thermocouple probes. It is supplied with the T-type Ultra Fast Thermocouple Probe and can be directly connected to a PowerLab with Pod ports or indirectly via the Pod Expander.
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.
Other signals
In addition to blood flow signals, PowerLab can also record other cardiovascular parameters simultaneously. More information is available at the following pages:
LabChartLabChart (for Windows and Macintosh) combines the familiar simplicity of a traditional strip chart recorder with the powerful analysis features of a digital acquisition system. LabChart software and a PowerLab data acquisition unit provide data integrity, easy selection of hardware settings, powerful online and offline analysis, procedure automation, seamless extraction of experimental data and flexible display options. Acquisition and analysis capabilities can be further increased with LabChart Extensions and LabChart Modules. LabChart Modules are available as part of
LabChart Pro and LabChart Extensions are free for download from the website for existing LabChart users.
Cardiac Output Module (Windows)The
MLS340/6 Cardiac Output Module provides easy extraction and calculation of cardiac output from small animals recorded in LabChart, using the thermodilution technique.
It provides:
- Automatic calculation of cardiac output in mL/min from a thermodilution curve
- Automatic calculation of baseline temperature and baseline slope correction
- Automatic calculation of the area under the curve
- Automated extraction of exportable parameters in a spreadsheet format
GLP and 21 CFR Part 11For 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.
Blood Flow Measurements
Laser Doppler Blood FlowMeterThe ADInstruments
ML191 Blood Flowmeter is a single channel laser Doppler flowmeter, which may be supplied with a variety of needle or surface probes and connects to any PowerLab data acquisition system. The surface and digit probes are MR compatible. Note: The laser Doppler technique detects mean flow over numerous vessels and is not used for determination of flow in a single vessel. For single vessel measurements, the invasive techniques mentioned below are more suitable.
Transit-Time Ultrasound Blood/Fluid Flow SystemsADInstruments provide flow systems and probes of various sizes for implanting in animals (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 blood flow measurements in milliliters per minute. The flow meters easily integrate with any PowerLab data acquisition systems.
These systems include:
Cardiac Ouput Measurements
ML313 Cardiac Output PodThe Cardiac Output Pod is used T-type thermocouples (thermodilution technique) to determine of cardiac output in small animals (mice, rats, guinea pigs or rabbits) ONLY. The Pod can be used with any appropriate T-Type thermocouples and has a 'delta' temperature mode to allow a signal offset to be applied so that small temperature variations are monitored accurately. The
Cardiac Output Module (Win only) for LabChart may be purchase to facilitate accurate and fast determinations of CO.
ML313C Cardiac Output Pod (with thermocouple)This configuration consists of the Cardiac Output Pod with additional products including:
- MLT1402 T-type Ultra Fast Thermocouple Probe with a fast response time of 0.005 seconds
- Cardiac Output Module (Win only) for LabChart
MLA313 Cardiac Output Accessory KitThis kit helps facilitate the measurement of cardiac output from small animals (rats, guinea pigs and mice). It can be used with the ML313C Cardiac Output Pod (with thermocouple) or ML313 Cardiac Output Pod (no thermocouple).
It includes:
- Hamilton LR (Luer tip) Glass syringe (250µl)
- Repeating dispenser
- Luer needle hubs
- Three-way stop-cocks
- Touhy Borst Adaptors
- Polyethylene tubing