These devices are used to measure blood pressure according to the original technique described by Riva Rocci and Korotkoff over a century ago. The measuring observer must be trained to use a stethoscope to auscultate the Korotkoff sounds over the brachial artery. This technique is usually referred to as conventional blood pressure measurement, or CBPM. Table

One model of the many mercury sphygmomanometers available, the PyMah (Pymah Corporation, Flemington, NJ), has been validated according to both protocols and is recommended. Because mercury sphygmomanometers generally adhere to a simple basic design with standard components, it is probably reasonable to assume that most, if not all, mercury sphygmomanometers would be of similar accuracy. The Hawksley sphygmomanometer, which is basically a mercury sphygmomanometer, has a zero-muddling feature to minimise observer bias, but its accuracy has been questioned. Table

The standard aneroid sphygmomanometer has only been formally validated according to the calibration procedure of the BHS protocol, and the results support reservations about aneroid devices because of their susceptibility to becoming inaccurate with use without this being apparent to the user. Table

If we accept that automated devices will in time replace the traditional mercury or aneroid sphygmomanometers and the stethoscope, all of which are necessary for measuring blood pressure according to the Riva-Rocci/Korotkoff method, then we must also prepare for the disappearance of the clinical technique to which we are so accustomed. Indeed, the influence of automated devices on this last measurement technique in clinical medicine is already apparent in the new generation of nurses and medical students. But might there not be more to the conventional auscultatory technique than meets the eye? The Riva-Rocci/Korotkoff technique may possess “that mystique peculiar to the clinical relationship, which is sensed by doctors and nurses and appreciated by patients.” Could it be this feature which makes clinicians so unhappy at having to relinquish the acquired skill inherent in the auscultatory technique, which for all its inaccuracies may possess subtle virtues “important in establishing the rapport from which a successful clinical relationship between doctor and patient may develop. This may or may not be the case, but it would seem reasonable to ask manufacturers of blood pressure measuring equipment to provide an electronic equivalent to the mercury column, so that the conventional auscultatory technique can live on. Indeed two such devices have been developed. These are the Greenlight 300 manufactured by AC Cossar & Sons, and the AccuSphyg. manufactured by Trimline. Table

Surprisingly manufacturers have been slow to produce automated sphygmomanometers for clinical use in hospitals to satisfy the large market that has arisen from the banning of mercury in some countries and the recommendation not to replace mercury sphygmomanometers in others, such as the UK and Ireland. There is evidence that the manufacturing industry is now aware of the need for an accurate automated device s to replace mercury sphygmomanometers. It is important that purchasing officers in the health services (whose responsibility it will be to order replacement automated devices for the traditional sphygmomanometer) are aware that protocols are in existence for validating blood pressure devices, and that evidence of independent validation should be demanded from manufacturers. Soundings from hospital authorities suggest that there is presently a tendency to substitute aneroid for mercury sphygmomanometers despite evidence that aneroid devices become inaccurate with use. Moreover, aneroid sphygmomanometry is prone to all the problems of the auscultatory technique, namely observer bias and terminal digit preference. Automated devices, by providing timed print-outs of blood pressure, remove these sources of error and thereby improve the overall accuracy of measurement, provided, of course, that they themselves are accurate. Table

Devices for measurement of blood pressure by occluding a digital artery in the finger are available, but because the problem of limb position is even more critical and because there is the additional problem of peripheral vasoconstriction affecting accuracy, this technique is not recommended. References to these devices may be found on the Library page. Table

There are two techniques for measuring ambulatory blood pressure (ABPM): the commonly used method of intermittent measurement of blood pressure over the 24-hour period, and the developing method of continuous waveform analysis.

The greatest number of validation studies have been conducted on ABPM devices, which measure blood pressure intermittently over the 24-hour period. Many of these devices have been validated in special groups, such as the elderly and pregnant women, and in differing circumstances, such as during exercise and in various postures. Table

The Portapres (TNO. Amsterdam), a portable recorder for 24 hour ambulatory monitoring, can provide beat-to-beat blood pressure monitoring which gives waveform measurements similar to intra-arterial recordings. However, the technique is subject to various inaccuracies, which the application of correction factors and digital filters in the latest model may remove, and the latest model is awaiting formal validation.