Accuracy of oscillometric blood pressure monitoring in pregnancy and pre-eclampsia

Objective To assess the accuracy of the Omron HEM 705 CP oscillometric device for the measurement of blood pressure in pregnancy and pre-eclampsia. Setting Two teaching hospitals. Participants Eighty-five pregnant women with a wide range of blood pressures, and 43 women with preeclampsia. Methods Evaluation was carried out according to the British Hypertension Society protocol, incorporating criteria of the Association for the Advancement of Medical Instrumentation (AAMI). Results Mean differences (device minus observer) for systolic blood pressure were -0.9 mmHg (SD 10) in normal pregnancy, and -2 mmHg (SD 10) in the women with pre-eclampsia. For diastolic blood pressure, Korotkoff phase V, the differences were -1.5 mmHg (SD 10), and -8 mmHg (SD 8) respectively; i.e. the device consistently under-read the diastolic blood pressure in pre-eclamptic women by a mean of 8 mmHg when compared with conventional sphygmomanometry. Korotkoff phase TV could not be accurately reproduced. According to the British Hypertension Society grading criteria, the device reached a 'B' grading in the 85 pregnant women. In pre-eclampsia only a 'C' grade was reached for systolic blood pressure, and 'D' grade for diastolic blood pressure. Accuracy criteria stipulated by the AAMI were not met in any situation. Conclusion The Omron HEM 705 CP does not reach acceptable accuracy criteria for blood pressure measurement when compared with trained observers in women with pre-eclampsia, as judged by the British Hypertension Society Protocol. It also failed to meet the AAMI criteria, although the methodology stipulated by the AAMI may not be applicable to a pregnancy population.