Abstract 12679: Clinical Applications and Comparison of the Oscar 2 and Spacelabs 90207 Ambulatory Blood Pressure Monitors (ABPMs) Using a Novel Dual Monitor Field Protocol

Abstract

Background: Our novel Dual Monitor Protocol and postural lab testing in 15 normotensives,15 hypertensives and 11 alcohol-dependents demonstrated that auscultatory ABPMs had problems assessing diastolic (DBP) and systolic pressures (SBP) with postural changes and misclassified up to 90% of DBPs and 20% of SBPs. Our lab studies of 11 normotensives and 4 hypertensives determined the oscillometric Oscar 2 and Spacelabs 90207 ABPMs overestimated SBP by ≥ 5 mm Hg for 87% (13/15) and 60% (9/15) of cases, respectively. GOAL . To apply our Dual Monitor Protocol in the field to compare values obtained by the Oscar 2 and Spacelabs 90207 ABPMs. Hypothesis: ABPMs will differ statistically and clinically depending upon the posture. Methods: A total of 9 field tests were conducted in 6 subjects either with 1 or 2 ABPMs. For dual monitor tests, ABPM clocks were synchronized and cuffs switched every 3 - 4 hr. Correction factors for each subject, specific to each ABPM and posture were used to adjust BPs from field tests. Results: All values = X ± SE, mm Hg . For 56 BPs over 24-hr in a normotensive, the Oscar overestimated observer-corrected SBPs by 8.7 ± 1.2 (135.5 ± 2.2 vs 126.8 ± 1.8, P < 0.001). For 101 simultaneous opposite arm BPs over 24 hr in a 66-yr old hypertensive, the Oscar was statistically (all P < 0.001) and clinically > Spacelabs for SBP (156.8 ± 1.2 vs 144.3 ± 0.9, Δ = 12.5 ± 1.0), MAP (118.8 ± 0.9 vs 110.7 ± 0.8, Δ = 8.1 ± 0.6) and DBP (99.8 ± 0.9 vs 95.2 ± 0.8, Δ = 4.6 ± 0.7). The Oscar overestimated (all P ≤ 0.001) the Spacelabs supine SBP (11.0 ± 1.7) and DBP (6.0 ± 0.7), seated SBP (10.8 ± 1.2) and DBP (3.5 ± 0.9) and standing SBP 16.4 ± 2.1) and DBP (5.5 ± 1.5). R was weakest for supine SBP (0.19, NS) and standing SBP (0.38, P < 0.05) and DBP (0.42, P < 0.05). Conclusions: These results are alarming despite our limited number of subjects. Oscar and Spacelabs ABPMs differ clinically and statistically and unlike auscultatory ABPMs are prone to significant SBP overestimation. To avoid SBP hypertensive bias and to obtain a more accurate representation of 24-hr BPs, values must be corrected for ABPM and Hg column lab postural Δs and converted to the phlebostatic axis. ABPM accuracy and reliability cannot be trusted until National and International validation protocols are revised to require multiple postural testing.