24-hr Ambulatory Blood Pressures Differ Significantly Based On The Monitor Chosen And The Age, Posture And Activity Of Each Subject

PURPOSE & METHODS: We used our Dual Monitor Protocol in the field and lab to compare the accuracy of Oscar 2 and Spacelabs 90207 ambulatory blood pressure monitors (ABPMs) versus two Observers using a Hg column and Thinklabs digital stethoscope. HYPOTHESIS: The Oscar and Spacelabs raw values would differ significantly from each other and from Observers. RESULTS: Values expressed as X ± SE mm Hg. In a 66-yr male, Oscar 24-hr systolic BP (SBP) was significantly higher than Spacelabs SBP (157 ± 1 vs 144 ± 1, ∆ = 13 ± 1, P < 0.001). Observer-corrected 24-hr SBP was similar to the Spacelabs in a 21-yr old male (both 119 ± 2, P > 0.05), but was lower than the Oscar in a 30-yr male (111 ± 1 vs 120 ± 2, ∆ = -9 ± 0.4, P < 0.001) and in a 19-yr male (127 ± 2 vs 136 ± 2, ∆ = -9 ± 1, P < 0.001). Oscar and Spacelabs ABPMs were prone to run-away inflations during cycling, climbing and walking and had a poor level of agreement compared to Observers in the lab. For 102 routine office BPs (n = 17), the Oscar overestimated Observers’ SBPs by ~10 mm Hg (P < 0.001, 95% CI: 8 - 12 mm Hg), while the Spacelabs overestimated by ~5 mm Hg (P < 0.001, 95% CI: 4 - 7 mm Hg). The Oscar differed from Observers by > ± 5 mm Hg for 94% of SBPs (16/17) and 35% of diastolic BPs (DBPs, 6/17), while the Spacelabs differed by > ± 5 mm Hg for 71% of SBPs (12/17) and 47% of DBPs (8/17). For 118 postural BPs (n = 12), the Oscar overestimated SBP for standing (P < 0.01) and DBP (P < 0.001) for supine measures, both by ~7 mm Hg. Spacelabs overestimated supine DBPs by ~7 mm Hg and underestimated standing DBPs by ~6 mm Hg (both P < 0.05). Oscar, avg 24-hr SBP corrections varied from -9 to +2 and for 24-hr DBP varied from -6 to +5. Spacelabs avg 24-hr SBP corrections varied from -9 to +5 and for 24-hr DBP varied from -2 to +10. In ABPM field tests, for 450 BPs over ~150 hr (n = 6), the Oscar overestimated SBP, MAP and DBP by ~5, 3 and 2 mm Hg (all P < 0.001), while the Spacelabs underestimated SBP, MAP and DBP by ~2, 3 and 5 mm Hg (all P < 0.001). CONCLUSIONS: BPs may differ statistically and clinically depending upon the ABPM chosen, and the age, posture and activity of subjects. Until national and international protocols require validation for postures and activities and identification of the characteristics of subjects used to develop proprietary equations, we cannot rely upon ABPM raw data for individual evaluations. American Foundation for Hypertension Research & Education, American Heart Association