Validation of electronic sphygmomanometers against mercury sphygmomanometers at high altitude in Tibet

Abstract

Objective: Studies at normal altitude generally showed that electronic sphygmomanometers (ES) yielded different readings from mercury sphygmomanometers (MS) but could be used as a substitute. Little is known about the performance of ES at high altitude, necessitating this validation study. Design and methods: In Dangxiong County in Tibet, 4300 m above sea level, a well-trained cardiologist measured the systolic (SBP) and diastolic blood pressure (DBP) of 129 adults (80 men, aged between 19 and 69, mean age 38) 3 times in a quiet roomwith proper room temperature. An ES (Omron HEM-759P) was connected with the MS by an air control valve and the bulb assembly served as the pressure source, allowing simultaneous measurement of BP using the 2 instruments. Results: Mean SBP measured by ES (124.67 ± 20.39 mm Hg) was significantly higher than by MS (118.91 ± 20.56 mm Hg) (5.76 mm Hg, p < 0.001) while DBPmeasured by ES (76.54±12.63mmHg) and byMS (76.95± 13.86mmHg) has no significant difference (− 0.42mmHg, p=0.228). Difference in SBP measured by ES and MS was more pronounced in men (6.84 mm Hg) than in women (4.00 mm Hg) (p = 0.002); and for DBP, no gender difference was found (− 0.93 mm Hg vs. 0.42 mm Hg, P=0.58). The Pearson's correlation coefficients betweenMSand ES were 0.974 for SBP (p < 0.001) and 0.961 for DBP (p < 0.001). The percentages of absolute differences between ES andMS in categories≤ 5 mm Hg, ≤ 10 mm Hg and ≤ 15 mm Hg for SBP were 50.4%, 82.2% and 96.1% respectively; and 86.7%, 99.2% and 100% for DBP respectively. Bland–Altman plots showed good consistency between MS and ES for both SBP and DBP measurements. Conclusion: To our knowledge, the first validation study conducted at high altitude demonstrated comparable differences between ES andMS as those at normal altitude. More studies are needed to firmly establish the usability of ES in high altitude.