Venous Occlusion Plethysmography

A plethysmograph device is used for measuring changes in volume within an organ or whole body. Some plethysmograph devices are attached to arms, legs or other extremities to determine circulatory capacity. 

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 can be 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, are made by Hokanson.

Blood flow in the human forearm (or calf) can be monitored non-invasively by venous occlusion plethysmography with a PowerLab system. Blood flow can be halted (venous occlusion) and restarted by an inflatable cuff placed on the upper limb.

Any PowerLab model is suitable for recording forearm plethysmography. Often a number of physiological signals are measured in these experiments, such a skin or core body temperature, ECG, pulse oximetry, finger pulse etc., so a 8 or 16 channel PowerLab is usually recommended.

Note: If continuous intravascular or non-invasive blood pressure measurements are also required then see the following:

Blood Pressure – Intravascular
Blood Pressure – Non Invasive

LabChart
LabChart (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.

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.
 

PowerLab Data Acquisition Systems
The PowerLab is a high-performance data acquisition unit suitable for a wide range of research applications. Typical applications include human and animal physiology, pharmacology, neurophysiology, biology, zoology, biochemistry, and biomedical engineering. Units are capable of recording at speeds of up to 400 000 samples per second continuously to disk (aggregate), and are compatible with instruments, signal conditioners and transducers supplied by ADInstruments, as well as many other brands. In addition to standard single-ended BNC inputs, 4 differential Pod ports are also available for direct connection of Pod signal conditioners and appropriate transducers. These systems include:

• ML866 PowerLab 4/30 - 4 Channels
  
• ML870 PowerLab 8/30 – 8 Channels
• ML880 PowerLab 16/30 – 16 Channels

Blood Flow Measurements

Laser Doppler Blood FlowMeter
The 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 Systems
ADInstruments 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 CO measurements in milliliters per minute. The flow meters easily integrate with any PowerLab data acquisition systems.

These systems include:

• ML870B11 One Channel Perivascular Flow System - ultrasonic blood flow system
• ML870B12 One Channel Tubing Flow System - measuring flow in tubing systems.
• ML870B13 Two Channel Perivascular Flow System - simultaneously measuring flow from two blood vessels
• ML870B14 Two Channel Tubing Flow System - simultaneously measuring flow from two tubing setups
• ML870B15 Two Channel Perivascular/Tubing Flow System - simultaneously measuring flow from a single blood vessel and single tube

Effect of Estrogen Replacement Therapy on Insulin Sensitivity of Glucose Metabolism and Preresistance and Resistance Vessel Function in Healthy Postmenopausal Women.

Satu Vehkavaara, Jukka Westerbacka, Tiina Hakala-Ala-Pietila, Antti Virkamaki, Outi Hovatta, and Hannele Yki-Jarvinen, Journal of Clinical Endocrinology and Metabolism, 4663-4670, 2000

Forearm blood flow was measured every 30 min with venous occlusion plethysmography using a mercury in silastic rubber strain-gauge apparatus (Model EC-4; Hokanson, Bellevue, WA), a rapid cuff inflator (Rapid Cuff Inflator model E20; Hokanson), and computerized analysis of flow curves (MacLab/4e). Peripheral vascular resistance was calculated by dividing mean arterial pressure in the brachial artery by forearm blood flow.

Effect of gender on vestibular sympathoexcitation.

Chester A. Ray, American Journal of Physiology: Regulatory, Integrative and Comparative Physiology, R1330-R1333, 2000

Multifiber recordings of leg muscle synaptic nerve activity (MSNA) were made by inserting a tungsten microelectrode into a peripheral nerve located behind the knee. Continuous measurements of arterial pressure and heart rate were made by a Finapres blood pressure monitoring unit (Ohmeda). Calf muscle blood pressure was measured in the contralateral leg to the nerve recording by venous occlusion plethysmography (Hokanson EC 4) using a mercury-in-Silastic strain gauge placed around the largest diameter of the calf muscles. The mean voltage neurogram, heart rate, arterial pressure tracing, and calf muscle blood flow were collected using a MacLab/8e. Total MSNA activity was calculated by summing the area of identified bursts for each minute using Peaks software.