Centron Diagnostics, a spin-out of King’s College London, recently released a blood pressure monitor that can measure peripheral and central systolic blood pressure with one upper arm cuff.
The cBP 301 monitor not only records the waveform of blood pressure at the arm, but uses uses a transfer function to calculate the central blood pressure with accuracy similar to radial tonometry. According to the company, its technology has been validated against invasive measurements of central aortic blood pressure.
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cSBP can be measured directly using a pressure sensor placed in the aortic root but this is impractical for most purposes. The approach most widely used at present is to obtain a peripheral blood pressure waveform by applanation tonometry of the radial artery (holding a pressure sensor against the radial artery). This waveform is then calibrated from an oscillometric measurement of peripheral blood pressure at the brachial artery and a mathematical transfer function used to transform the radial artery waveform into a central pressure waveform from which cSBP can then be derived. Concerns as to the applicability of a generalised transfer function to all patients have now largely been dispelled. The approach is justified because, for a given waveform morphology, the upper limb arteries (the physical properties of which change little with ageing) exert a relatively predictable influence on waveform amplification. It is now accepted that the accuracy of this approach is limited by the accuracy of the peripheral blood pressure measurement.5 Thus cSBP can only be as accurate as the peripheral blood pressures used to calibrate the waveforms.
Radial tonometry requires a skilled operator, specialist equipment and is relatively time consuming. Centron Diagnostics approach to estimating central systolic blood pressure is to obtain a peripheral blood pressure waveform from a brachial blood pressure cuff. Although such a waveform differs from that obtained using an intra-arterial sensor or from that obtained by tonometry, an appropriate transformation† can be used to estimate cSBP with similar accuracy as that achieved by tonometry. This approach allows cSBP to be estimated at the same time as a routine oscillometric measurement of peripheral blood pressure with no extra equipment or expertise required. The peripheral blood pressures are derived using SunTech Medical’s fully validated oscillometric technology.
Product page: cBP 301
Press release: King’s spin-out company launches new technology