Differences between casual and 24-h blood pressures.

Casual (office) blood pressure measurements using the conventional cuff method are open to a number of errors which are well recognized, e.g. errors due to large arm size, small cuff bladder, digit preference, variations in environmental temperature, smoking and/or coffee ingestion and lastly the 'defence' or alerting reaction. Although the latter error may be reduced by the habituation induced by repeated measures, it may not be so extinguished in some subjects. As an incidental finding in a trial of four different beta-blocking agents we were surprised to find how common this was. We had to reject about one-third of the subjects recruited as hypertensive on the basis of at least three cuff readings, when we found their intra-arterial pressures were normal away from hospital. Raftery and his colleagues in London have claimed that intra-arterial recordings eliminate the common placebo induced fall in blood pressure, which would greatly simplify the testing of new hypotensive drugs, particularly if it could be shown that ambulatory recordings made by non-invasive methods also removed this artefact. Others have used multiple non-invasive methods of blood pressure measurement with the Remler device and found similar results. In general the pressures taken at home are less than office pressures. Pickering and his colleagues in New York have found this discrepancy is particularly large in subjects with borderline hypertension. Littler et al. were one of the few groups to record higher pressures at home compared with hospital.(ABSTRACT TRUNCATED AT 250 WORDS)