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In praise of mercury sphygmomanometers

2001; BMJ; Volume: 322; Issue: 7296 Linguagem: Inglês

10.1136/bmj.322.7296.1248

0959-8138

Alan Murray,

Cardiovascular Health and Disease Prevention

Editor—Users of mercury sphygmomanometers are being advised to consider alternatives, but this is causing problems.1,2 Currently there is confusion over the advantages and disadvantages of the alternatives. The mercury sphygmomanometer, when used by trained staff, is the gold standard. Aneroid devices are also in widespread use, but they can be knocked out of calibration easily. These devices can be used, provided they are recalibrated every six months, but indications are that this advice is rarely taken. Automated devices are now readily available. The British Hypertension Society states that for these devices to be acceptable, no more than 25% of measurements should be in error by more than 10 mm Hg and no more than 10% by 15 mm Hg.3 Automated devices have a well accepted role in monitoring changes in blood pressure but a more limited one in determining absolute blood pressure. The combined recommendation of the European Society of Cardiology, the European Society of Hypertension, and the European Atherosclerosis Society is quite clear—automated devices are unsuitable as a routine substitute for the measurement of clinic blood pressure in the diagnosis of hypertension and not appropriate for determining the need for treatment and for assessing treatment efficacy.4 Concerns have been expressed to the European Standards Committee for sphygmomanometers that the current degree of clinical accuracy required by the standard for automated devices is inadequate. Some would like to see noticeable improvements, but manufacturers will resist this strongly, simply because better accuracy cannot yet be achieved and, as O'Brien points out, the oscillometric techniques cannot measure blood pressure in all situations.5 Clinical users must decide when automated devices are appropriate and when they are not. We should not allow the argument that clinical staff are poor at taking manual measurements to influence decisions. Clinical staff can be trained. The looming difficulties over the measurement of blood pressure have been clear for some years. Recognising this, at the Freeman Hospital and the University of Newcastle, we developed a manual device in collaboration with a manufacturer of traditional sphygmomanometers. This modern electronic device is an accurate alternative to the mercury sphygmomanometer, with features to improve measurement technique and to provide automatic recalibration when switched on. Standards can help by weeding out poor quality devices but they do not recommend which devices should be used. A clinical decision must be made when selecting between manual and automated devices.