aAustralian School of Advanced Medicine, Macquarie University, Sydney, Australia
bChair of Cardiovascular Medicine, Department of Health Sciences, University of Milano-Bicocca
cDepartment of Cardiology, S.Luca Hospital, IRCCS Istituto Auxologico Italiano, Milan, Italy
Correspondence to Gianfranco Parati, Department of Cardiology, S.Luca Hospital, Istituto Auxologico Italiano & University of Milan-Bicocca, Piazza Brescia 20, Milan 20149, Italy. Tel: +39 026 1911 2949; fax: +39 026 1911 2956; e-mail: email@example.com
The seminal demonstration of the use of the brachial cuff for measurement of arterial pressure by Scipione Riva-Rocci in 1896  was a result of a series of iterations over a number of years throughout the latter part of the nineteenth century. A large number of highly motivated individuals sought to obtain a reliable method to quantify the force of the arterial pulse that, until the end of the nineteenth century, could be evaluated only by manual palpation. The simplicity by which Riva-Rocci showed how the level of pressure in the cuff is related to the appearance of the pulse in the radial artery, thus, offering a way to obtain a quantitative measure of peak systolic pressure, was one of pure technical elegance.
The concept of associating the arterial pressure with other external phenomena that can be detected and analyzed has been the cornerstone of all advances made in the noninvasive measurement of blood pressure. The second most important advancement was related to the ability of the stethoscope to detect audible signals associated with haemodynamic phenomena of disturbed flow in conduit arteries. This was formalized by Korotkoff in 1905  to associate appearance and disappearance of sounds heard over the artery distal to the Riva-Rocci cuff with systolic and diastolic pressure, respectively. Thus, with the auscultatory technique, the brachial cuff sphygmomanometer, along with the stethoscope, became one of the most indispensable and enduring instruments in medicine.
Notwithstanding the groundbreaking advances of Riva-Rocci and Korotkoff, there are substantial limitations and deficiencies with the conventional cuff sphygmomanometer with respect to the consistency and reproducibility of the measurement. From the very beginning it was realized that the cuff width proposed by Riva-Rocci was too small, resulting in a nonuniform distribution of the occlusive force, leading to substantial variability in the palpatory detection of the arrival of the pulse at the wrist. This was later corrected by proposing cuffs of a larger size. In addition, whereas the discrete onset of the Korotkoff sound is generally reliable, and so the detection of systolic pressure, the disappearance is often not as discrete and is frequently confounded by muffling sounds. This presents difficulty in the detection of diastolic pressure and relies on, at times, a qualitative decision by the operator.
In addressing the characteristic limitations of the auscultatory method, the pioneering work of Les Geddes has resulted in the global acceptance of the oscillometric technique for blood pressure measurement [3,4], which is essentially operator independent. This method analyses the small pressure oscillations in the cuff during the change in cuff pressure as it descends from suprasystolic values. The actual physical pressure measurement in this technique is related to the mean arterial pressure, which is the cuff pressure corresponding to the maximum amplitude of the oscillations, as at this pressure, the arterial wall is unloaded and so undergoes maximal expansion. Systolic and diastolic pressures are determined by empirical algorithms detecting relative changes in amplitude from the maximal values at the beginning and end of the oscillogram, respectively. Analogous to variability in the auscultatory technique due to inconsistencies of the Korotkoff sounds, the oscillogram has a certain amount of variability and inconsistency in terms of asymmetry and nonuniformity of the pulsations, with potential errors in derived values of systolic and diastolic pressure. However, although attempts are made to minimize these potential errors with mathematical and statistical optimization of algorithms, at the same time improved techniques are being continually sought that might eliminate operator dependency as well as improve the reliability of automated noninvasive measurement and monitoring of arterial blood pressure .
The study by Fujikawa et al. in this issue of the Journal reports a potential and significant improvement on the existing techniques. In a similar manner to the oscillometric method, their technique exploits the oscillogram present in the occluding cuff during change of cuff pressure between the systolic and diastolic phase of circulation. However, whereas the conventional oscillometric methodology compares changes in amplitude of the oscillogram at different cuff pressures, the methodology of Fujikuwa et al. compares changes in pulse arrival times. This work is a continuation of previous studies by some of the same authors in the group [7–9]. In these previous studies, a second smaller cuff was added to the conventional cuff so as to detect the pulse arrival time over the distance of the large occlusive cuff. Although this was able to detect gross changes, the technique still suffered from the similar deficiencies of the original brachial cuff of Riva-Rocci, that is, that of nonuniform occlusion leading to pulse dispersion errors in travel times. In this present study  a third cuff was added so as to provide a more evenly distributed and reliable arterial occlusion resulting in a more fiducial detection of the rapid increase in pulse arrival times at cuff pressures corresponding to systolic arterial pressure, and of the cessation of change in pulse arrival time corresponding to diastolic pressure.
The validation of the triple cuff sphygmomanometer reported by Fujikuwa et al. indicates a potentially robust technique which performs well, in the context of the internally accepted guidelines of professional hypertension societies  as well as of the recommendations issued by the American National Standards Institute and the Association for the Advancement of Medical Instrumentation, when compared with established auscultatory, oscillometric and invasive pulse transit time methods under highly controlled conditions. The implications of these findings are that the association of cuff pressure with measurements of time rather than of cuff pulse amplitude could provide a better paradigm for the quantification of arterial pressure. Although this has not yet been convincingly demonstrated, present findings suggest that the methodology of detection of pulse travel time can perform at least as well as the auscultatory or oscillometric methods over a large pressure range (systolic range 92–209 mmHg; diastolic range 53–117 mmHg). In this pressure range the spread of errors is relatively uniform, which indicates that the smaller cuffs for occlusion and pulse detection do not contribute to any systematic bias and that the cuff errors are not sensitive to levels of arterial pressure. Presumably, further studies will provide similar ranges of errors with respect to age as well as arm size with suggestions of specific sizes of each of the three cuffs so as to optimize the uniformity of arterial occlusion and the reliability of pulse detection.
In recent years, there has been rapidly rising interest in the use of pulse wave analysis for the noninvasive measurement of central aortic pressure for improved assessment of cardiovascular function . The validation of these techniques, wherein algorithms are used to analyze the peripheral pulse in order to estimate central aortic pressure, requires the measurement of blood pressure for calibration. When this is done using directly measured arterial pressure, there is a high correlation between the estimated and measured central aortic pressure . However, when the signals are calibrated using pressures measured noninvasively, the differences between directly measured and estimated aortic systolic pressure are related mainly to the differences due to the conventional arm cuff blood pressure readings taken through a single cuff brachial sphygmomanometer . Further studies are awaited on the novel triple cuff sphygmomanometer to establish whether the inherent limitations of the brachial cuff, which have been present since the significant advances made by Riva-Rocci, Korotkoff and Geddes, can be markedly reduced or even eliminated.
Conflicts of interest
There are no conflicts of interest.
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