Blood Pressure - Non Invasive
Overview:
Blood pressure is a widely used parameter in cardiovascular assessment. Therefore non-invasive blood pressure recording methods are important as invasive blood pressure recordings may not always be possible.
Non-invasive blood pressure recording methods need particular care to ensure reproducible and accurate recordings. These methods are often inaccurate 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.
Method:
Non-Invasive Techniques for HumansNon-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 MLT1100/D Sphygmomanometer or MLT1100/A Sphymomanometer and peripheral blood flow in the finger measured using a few methods.
A piezo-electric element to convert force applied to the active surface of the transducer from the finger blood pressure pulse, into an electrical signal:
- MLT1010 Piezo Electric Pulse Transducer
- Connects directly to the BNC input of a PowerLab
- MLT1010/D Piezo Electric Pulse Transducer
- Connects directly to the DIN input of a PowerLab
An infrared photoelectric sensor used to record changes in blood volume as the arterial pulse expands and contracts the microvasculature:
- MLT1020EC IR Plethysmograph - Ear Clip
- Connects directly to a PowerLab Pod port or can be used with a GP Amp or Bridge Amp connected to a PowerLab.
- MLT1020FC IR Plethysmograph - Finger Clip
- Connects directly to a PowerLab Pod port or can be used with a GP Amp or Bridge Amp connected to a PowerLab
- MLT1020PPG IR Plethysmograph - Velcro Strap
- Connects directly to a PowerLab Pod port or can be used with a GP Amp or Bridge Amp connected to a PowerLab
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.
The volume-clamp method involves measuring the finger arterial pressure using a finger cuff and an inflatable bladder in combination with an infrared plethysmograph. This method changes the pressure of the finger cuff using a fast pressure control system to match intra-arterial pressure and transmural pressure across the finger arterial walls is zero. Changes in cuff pressure provide an indirect measure of intra-arterial pressure.
MLE1054 Finometer® MIDI is a non-invasive continuous blood pressure measuring system used to monitor the brachial arterial pressure using a finger arterial pressure measurement. The Finometer can be connected to a PowerLab to provide a display of the brachial artery reconstruction from the finger pressure and beat-to-beat values of Systolic, Diastolic and Mean pressure. It features hydrostatic height correction, remote and automatic control. Optional hardware may be ordered separately for recording ECG, viewing the finger pressure waveforms, and calculating Cardiac Output using FMS’s Beatscope software.
Oscillometry
Peripheral blood flow to the arm or wrist is occluded using an inflatable cuff (sphygmomanometer). 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 MLT1100/D Sphygmomanometer. The sphygmomanometer is coupled to a non-invasive pressure transducer that connects directly to a PowerLab with Pod ports or via the ML305 Pod Expander or ML221 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 MLT1100/D Sphygmomanometer and MLT206 Electronic Stethoscope. The Electronic Stethoscope connects directly to the PowerLab BNC input.
Non-Invasive Techniques for Animals
ADInstruments supply a number the NIBP systems used conjunction with a PowerLab system to obtain non-invasive blood pressure measurements from tails of rodents (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 a specialized tail cuff and pulse transducer to intermittently measure blood pressure based on the periodic occlusion of tail blood flow.
Software:
LabChart
LabChart software (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.
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.
Hardware:
Non-Invasive Blood Pressure System (Beat to Beat)
- MLE1054-V Finometer MIDI
- This is a non-invasive stationary blood pressure measurement and beat to beat hemodynamic monitoring system for human subjects. The Finometer captures the continuous blood pressure waveform and automatically computes up to15 beat to beat hemodynamic parameters including Cardiac Output (CO),Stroke Volume (SV), Total Peripheral Resistance (TPR), Pulse Rate Variability (PRV) and Baroreflex Sensitivity (BRS). Specify mains voltage V= 115 or 220.
Bridge Amplifiers
- ML221 Bridge Amp
- ML224 Quad Bridge Amp
- ML228 Octal Bridge Amp
- ML142 GP (General Purpose) Amp
- ML305 Pod Expander
Tonometer
- SPT-301 Non-Invasive Pulse Tonometer
- A hand-held wand probe equipped with a Mikro-Tip pressure sensor at the tip, designed for non-invasive recording of pulse pressure wave contours and requires an AEC-10C Catheter Interface Cable for connection to any ADInstruments bridge amplifiers.
Non-Invasive Blood Pressure Measurements in Humans
Sphygmomanometers and Transducers
Non-Invasive Blood Pressure Measurements in Animals
Non-Invasive Blood Pressure Systems
- ML125/R NIBP System (for Rats with tail diameters ≤ 10 mm)
- ML125 NIBP Controller
- MLT125/R Pulse Transducer and Tail Cuff (suitable for rats)
- ML125/M NIBP System (for Mice with tail diameters ≤ 6 mm)
- ML125 NIBP Controller
- MLT125/M Pulse Transducer and Tail Cuff (suitable for mice)
Rat Restrainers
- MLA5020 Rodent Restrainer (80 to 200 g)
- MLA5022 Rodent Restrainer (180 to 320 g)
- MLA5024 Rodent Restrainer (300 to 440 g)
- MLA5025 Rodent Restrainer (440 to 550 g)
Mouse Restrainers
- MLA5016 Rodent Restrainer (up to 35 g)
- MLA5018 Rodent Restrainer (up to 50 g)
Raised blood pressure, not renin–angiotensin systems, causes cardiac fibrosis in TGR m(Ren2)27 rats.
Jill E. Bishop, Linda A. Kiernan, Hugh E. Montgomery, Peter Gohlke, Jean R. McEwan, Cardiovascular Research, 57-67, 2000
Exercise-induced muscle injury augments forearm vascular resistance during leg exercise.
Chester A. Ray, Edward T. Mahoney, and Keith M. Hume, American Journal of Physiology: Heart and Circulatory Physiology, H443-H447, 1998
Sympathetic nerve activity during natural stimulation of horizontal semicircular canals in humans.
Chester A. Ray, Keith M. Hume, and Samuel L. Steele, American Journal of Physiology: Regulatory, Integrative and Comparative Physiology, R1274-R1278, 1998
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.
