Accuracy of SpaceLabs 90207 is altered by venous blood redistribution

Validation protocols that have been introduced for automated blood pressure (BP) measuring devices recommend procedures carried out at rest only. We aimed to determine whether venous blood redistribution affects the accuracy of the oscillometric method of BP measurement. For this purpose, we chose a popular oscillometric ambulatory BP monitor -- the SpaceLabs 90207 (Osc). Lower body negative pressure (-40 mmHg) (LBNP) was used to simulate changes of body position. Fifty-one young healthy volunteers had their BP measured simultaneously by Osc and mercury sphygmomanometer (HgS) at rest (min 3 and 5), during LBNP (min 7 and 9) and after LBNP (min 11). Differences (Delta, mmHg) between HgS and Osc for systolic (SBP) and diastolic BP (DBP) were calculated for every measurement minute. For SBP, DeltaSBP-7 and DeltaSBP-9 were significantly different from DeltaSBP-5 (0.65 +/- 2.6 and 0.33 +/- 2.4 mmHg vs -0.80 +/- 2.9 mmHg, p < 0.003 and p < 0.02, respectively). DeltaSBP-11 also differed significantly from DeltaSBP-3 and DeltaSBP-5 (1.16 +/- 2.5 mmHg vs -0.06 +/- 3.1 mmHg and -0.80 +/- 2.9, p < 0.01 and p < 0.00007, respectively). When graded according to British Hypertension Society protocol, Osc remained in the A class in every measurement minute. The accuracy of SpaceLabs 90207 is altered by venous blood redistribution. These inaccuracies may constitute an additional limitation of oscillometric ambulatory BP monitoring.