New instruments for measuring blood pressure.

The development of the conventional indirect method of blood pressure measurement was essentially complete by 1905, 70 years ago. The method has certain shortcomings, but these can be offset to a large degree by control over conditions of measurement, provision of proper apparatus, and intensive training of observers. Still, there are potential advantages which might be met by an acceptable automated device. An experimental evaluation of five such devices led to rejection of each of them on grounds of inadequate measurement performance, mechanical failures, or both. Only the Random-Zero device (Hawksley) among the instruments tested, gave good performance in comparison with the conventional method and was free of serious mechanical disadvantages. Evaluation of new devices will continue to be of great importance, and proposed guidelines for such studies are reviewed.