Direct versus indirect measurement of blood pressure.

The indirect method of blood pressure measurement is known to be potentially inaccurate, slow-moving and incapable of recognizing artefacts such as the 'alerting reaction'. This situation can be improved by repeated measurements, with, for example, ambulatory non-invasive measurement. Nevertheless, these clinic blood pressure measurements are known to supply very good prognostic information, at least in large populations, and it has yet to be established that ambulatory monitoring can supply better prognostic data. The direct technique, in contrast, is of known and measurable accuracy, records every pressure pulse and can recognize all artefacts. Unfortunately, the direct technique has no general clinical application because of its invasive nature, and there is a need to break with conventional thinking and develop a new technique that can match the direct technique without the need for physiological invasion.