Measurement of arm blood pressure using different oscillometry manometers compared to auscultatory readings

Five different semiautomatic manometers were tested, where oscillometry is the measuring principle. Three of the manometers (Omron R4, A&D UB 322 and Braun) were wrist manometers, where the occluding cuff is placed around the volar surface of the wrist. Two of the manometers (A&D UA 777 and Omron M4) measure on the upper arm. The investigation included 72 patients with systolic blood pressure (SBP) ranging between 110 and 200, and diastolic blood pressure (DBP) between 62 and 114 mmHg. Forty-five of the subjects were on antihypertensive medication when the manometer tests were carried out. Each of the manometers was tested with double measurements of blood pressure against 2 x 2 auscultatory measurements done before and after the semiautomatic readings. The auscultatory measurements are all performed by the same observer, who was blinded for the measurements with semiautomatic manometers. The mean difference between the oscillometric recordings compared to auscultatory measurements varied from +1.2 to -8.5 mmHg for SBP and from -0.5 to -8.3 mmHg for DBP. However, the interindividual differences varied considerable with standard deviation of the difference varying from 8 to 18 mmHg for SBP with the highest values for wrist manometers. Concerning DBP, the standard deviation of difference for all five manometers was between 6 and 8 mmHg, with the highest values for wrist manometers. None of the tested manometers fulfilled the criteria for grading A or B in the previously introduced grading by the British Hypertension Society. To conclude, the upper-arm manometers have a measuring accuracy for SBP a little higher than that of the wrist manometers, while there is no bigger difference in the measuring accuracy of DBP. The most important point is that the measuring accuracy in a single patient is unpredictable. If home readings are prepared, a test of the accuracy against auscultatory recordings should be done in every single patient. In the clinical wards, it is important to be aware of the measuring accuracy if oscillometric measurements are introduced replacing auscultatory measurements.