Objective: To establish the accuracy the Welch Allyn 'Vital Signs' blood pressure monitor in pregnancy and pre-eclampsia according to a modified British Hypertension Society protocol.
Design: Prospective observational study.
Setting: Maternity Unit/Obstetric Ward, Guy's and St Thomas' Hospital, London, UK.
Population: Forty-three pregnant women of whom 12 had pre-eclampsia.
Methods: Nine sequential same-arm measurements were taken from each woman by two trained observers, alternating between a mercury sphygmomanometer and the device. The last seven readings were analysed according to the British Hypertension Society protocol. The accuracy of the device was determined using the grading scale indicated by the British Hypertension Society protocol (grade A/B = pass, grade C/D = fail).
Main outcome measures: Grading criteria of the British Hypertension Society Protocol.
Results: The Welch Allyn 'Vital Signs' monitor achieved a grade A for both systolic and diastolic pressures in pregnant women who did not have pre-eclampsia. In those women with pre-eclampsia, it achieved a grade D and B for systolic and diastolic pressures, respectively. The mean differences between the observers and the device in women without pre-eclampsia were -2.6 (6.4) and -1.5 (7.2) mmHg for systolic and diastolic pressures [and in pre-eclamptic women -7.8 (6.3) and -5.5 (6.5)mmHg]. It therefore fulfils criteria set by the Association for the Advancement of Medical Instrumentation (mean <5 mmHg and standard deviation <8 mmHg) in pregnancy, but not in pre-eclampsia.
Conclusion: This is the first automated device suitable for robust clinical use that can be recommended for use in pregnancy. However, it should be borne in mind that-similar to other devices--it significantly under--recorded readings obtained in pre-eclamptic women.