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Blood Pressure - Non Invasive
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| PowerLab systems may be used to record non-invasive blood pressure measurements using a variety of techniques.
Non-invasive methods for determining blood pressure require particular care to ensure reproducible and accurate recordings. These methods are often compromized due to difficulties in calibration. Continuous recordings are often impractical as the technique requires partial or total occlusion of blood flow. If occlusion techniques are applied, it is important to ensure that the ischemic period is limited.
Techniques for Human Applications
Non-invasive blood pressure recordings are commonly obtained using peripheral blood flow occlusion, oscillometric, auscultation, tonometry or volume clamping techniques.
Peripheral Blood Flow Occlusion
Systolic blood pressure may be determined by the return of peripheral blood flow following arterial occlusion. The brachial arterial may be occluded using a Sphymomanometer and peripheral blood flow in the finger measured using either the:
Oscillometry
This technique applies an inflatable cuff (sphygmomanometer) to the arm or wrist to occlude peripheral blood flow. A pressure transducer is then used to record the pressure oscillations within the cuff following the return of blood flow.
Basic oscillometry can be performed using the ADInstruments Sphygmomanometer. The sphygmomanometer is coupled to a pressure transducer that connects directly to a PowerLab with Pod ports or via the Pod Expander or Bridge Amp, thereby providing measurements of cuff pressure. As the cuff pressure oscillations are overlaid on a constantly decreasing baseline when reducing the cuff pressure, data smoothing and arithmetic calculations are required to correctly identify pressure oscillations. This can be easily performed using Smoothing (Savitzky-Golay) and Arithmetic functions in the LabChart software.
Auscultation
This technique also involves occlusion of arterial blood flow using an inflatable cuff; however, rather than using cuff oscillations to determine the systolic and diastolic blood pressures, a stethoscope is applied to the brachial artery to detect Korotkoff sounds following resumption of blood flow.
Auscultation techniques can be performed using the Sphygmomanometer and Electronic Stethoscope. The Electronic Stethoscope connects directly to the PowerLab BNC input.
Tonometry and Volume-Clamp Techniques
Third-party products that operate according to tonometry or volume-clamp techniques may connect to PowerLab data acquisition systems provided that they have a suitable analog output (± 10 V). The signal may then be analyzed using the LabChart software.
Non-Invasive Blood Pressure Measurements in Animals
ADInstruments supply a number of systems and related apparatus for non-invasive blood pressure measurements in rats and mice using methods similar to the peripheral blood flow occlusion technique discussed above. These systems operate by occluding blood flow to the tail using specialized cuffs and measuring the pulsatile blood flow distal to the cuff.
For rodent use, ADInstruments supply the:
These systems include the: - NIBP Controller: This unit is used with a PowerLab system with the pressure and pulse signals relayed via BNC connections. The LabChart software can be used to control the NIBP Controller at pre-set times.
- Pulse Transducer and Tail Cuff
- Rodent restrainers are also available in various sizes for use with mice and rats (up to 550g).
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 infromation, visit the Good Laboratory Practice application page or contact your nearest ADInstruments representative.
More information: |
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| PowerLab (MacLab) citations: |
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| Raised blood pressure, not renin‚angiotensin systems, causes cardiac fibrosis in TGR m(Ren2)27 rats. |
| J.E. Bishop, L.A. Kiernan, H.E. Montgomery, P. Gohlke, J.R. McEwan;
Cardiovascular Research, 47, 57-67, 2000 |
| Under light general anaesthesia, weight and systolic blood pressure were assessed (tail cuff photoplethysmography: mean of five readings per animal: MacLab Bioamplifier ML-130, and IITC Mod 29 Pulse Amplifier and tail cuff system IITC Life Sciences, Woodland Hills, CA, USA).
Exercise-induced muscle injury augments forearm vascular resistance during leg exercise.
C.A. Ray, E.T. Mahoney, K.M. Hume, American Journal of Physiology:
Heart and Circulatory Physiology, 275, H443-H447, 1998
Continuous measurements of arterial blood pressure and heart rate were made using a Finapres blood pressure monitoring unit (Ohmeda, Englewood, CO). Forearm blood flow was measured by venous occlusion plethysmography (Hokanson EC 4 plethysmograph, D. E. Hokanson, Bellevue, WA) using a mercury-in-Silastic strain gauge ... Forearm blood flow was measured at 15 s intervals. Forearm vascular resistance was calculated by dividing mean arterial pressure by forearm blood flow. All data were collected on-line (MacLab/8e) |
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| Sympathetic nerve activity during natural stimulation of horizontal semicircular canals in humans. |
| C.A. Ray, K.M. Hume, S.L. Steele, American Journal of Physiology:
Regulatory, Integrative and Comparative Physiology, 275, R1274-R1278, 1998 |
| Multifiber recordings of skin and muscle SNA were made with a tungsten microelectrode inserted in the peroneal nerve. A reference electrode was placed subcutaneously 2‚3 cm from the recording electrode. ... The nerve signals were amplified, filtered with a bandwidth of 700‚2000 Hz, and passed through a resistance-capacitance integrating network with a time constant of 0.1 s to obtain a mean voltage display of the nerve activity. Continuous measurements of arterial blood pressure and heart rate were made using a Finapres blood pressure monitoring unit (Ohmeda, Englewood, CO). Changes in skin blood flow were determined by laser Doppler (ALF21D, Advance, Tokyo, Japan). The flow probe was placed on the top of the foot (dorsal aspect), where stroking of the skin elicited skin afferent fiber discharge. Skin vascular resistance was calculated as mean arterial pressure divided by skin blood flow. All data were collected online (MacLab 8e). The mean voltage neurograms, blood pressure tracing, and blood flows were routed to an online computer for monitoring and data collection purposes throughout the study. |
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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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