Background and objective: Measurement of blood pressure by using the auscultatory method coupled with mercury sphygmomanometer is rapidly being replaced for monitor using the oscillometric one. Discrepancies between the two methods and the factors related to them were analyzed in a large subset of adults.
Material and method: Blood pressure values were obtained sequentially in the same arm by using a mercury sphygmomanometer and a Spacelabs monitor devices. The relationship between both kinds of measurements was assessed by the Pearson's correlation coefficients and the concordance by using the Bland and Altman method. Differences between the two methods were calculated and the factors related to the differences were sought by multiple regression models.
Results: A total of 1,742 adult subjects were analyzed. Pearson's correlation coefficients were 0.927, 0.922, 0.886, 0.962 for SBP, DBP, MBP and PR, respectively. Oscillometric method overestimate and infraestimate SBP values in the two extreme of SBP values, the lowest SBP the highest the values and vice versa. A similar trend was observed for DBP although the differences were minor. Pulse wave amplitude explains the 24% of the variance observed for SBP and arm circumference the 8% for DBP.
Conclusions: Blood pressure values measured by oscillometric methods are influenced for pulse wave amplitude and by the arm circumference. These need to be taken in account when blood pressure assessment is obtained by using this method.