INVESTIGATION OF AMBULATORY BLOOD-PRESSURE MONITORING DATA EDITING CRITERIA

Ambulatory blood pressure monitoring (ABPM) allows multiple measuremen ts of BP over a 24h period but often produces a proportion of measurem ents which are distant from the mean and unlikely to be genuine. The s oftware which accompanies the SpaceLabs 90207 monitor requires criteri a to be set which excludes outliers (autoediting) but there is no publ ished data evaluating at what levels these autoediting criteria should be set. This study set out to ascertain whether outlying BP measureme nts represent true blood pressures or machine error, the determinants of machine error and appropriate autoedit criteria. Twenty subjects, b oth normotensive and hypertensive, were studied by ABPM with a blinded observer recording BP using a standard mercury sphygmomanometer (SMS) connected via a T-tube during three activity phases: sitting with cuf fed arm still, walking but keeping arm still during measurement and si tting but gently moving the arm during measurement. The results show t hat a high ABPM/SMS discrepancy is associated with arm movement. After studying different autoediting criteria which aimed to eliminate the maximum number of conflicting readings while excluding the minimum num ber of unconflicting readings, an autoediting threshold of between 1.7 5 and 2 s.d.s from the mean based separately on sleep and awake measur ements is suggested.