The mean pressure at the upper arm is underestimated when calculated using the traditional formula of adding one-third of the pulse pressure to the diastolic pressure. This underestimation can be avoided by adding 40% of pulse pressure to the diastolic pressure. The proposed approach needs to be validated through larger scale studies.

Mean arterial pressure (MAP) is defined as the average arterial blood pressure (BP) during a single cardiac cycle [1]. MAP is of clinical importance as it reflects the hemodynamic perfusion pressure of the vital organs. As the shape of the pressure wave is not available during routine BP measurements at the upper arm, a simple textbook formula is generally used in which one-third of the pulse pressure (PP) is added to diastolic pressure to calculate MAP [2][3][4].The shape of the arterial pressure wave determines which percentage of the PP has to be added to diastolic pressure to calculate MAP correctly. We recently challenged the validity of the traditional formula to calculate MAP [5]. We showed that the real MAP at the upper arm is underestimated by the traditional formula. This underestimation can be overcome by adding 40% of PP to the diastolic pressure. As the study population consisted mainly of elderly and hypertensive subjects, the general applicability of the newly proposed formula was, rightfully, questioned [6]. In the current study we investigated the general validity of the newly proposed formula in a larger study population, consisting of subjects of all ages and with a wider range of BPs and heart rates.One hundred subjects aged 19-91 (mean 56 AE 17 SD), of which 49 were women, were included in this study. The study was approved by the local ethical committee. All patients gave their informed consent. Sex, age, arm circumference, medication, smoking behavior, medical history and heart rate were obtained. BP was measured twice at the right arm with a sphygmomanometer (Speidel & Keller, Jungingen, Germany; Maxi Stabil 3, cuff size 14 Â 53 cm) and the Korotkoff sound technique using a stethoscope. Pressure measurements were performed while the subjects were sitting on a chair with the arm at heart level. Cuff deflation rate was approximately 2.5 mmHg/s. Measurements were performed by a trained observer [7]. The mean of two, diastolic and systolic BP, measurements were used to determine the BP level. The shape of the pressure wave was acquired at the brachial artery using an applanation tonometer (Sphygmocor pulse wave analysis system, model SCOR-Px; AtCor Medical Pvt. Ltd, Sydney, Australia). The applanation tonometer, connected to an electronic module, can noninvasively record a patient's peripheral artery BP waveform. These pressure waves do not differ significantly from intraarterially recorded pressure waves [8]. Systolic and diastolic readings were imported into the software of the applanation tonometer. MAP was subsequently determined by integrating the pressure wave. Data analysisMAP obtained by tonometry was used as a reference, the 'real' MAP. We calculated what percentage of PP had to be added to diastolic pressure to obtain this real MAP. Real MAP was compared with MAP calculated either with the traditional formula (0.33 PP þ diastolic pressure) or by the new proposed formula (0.4 PP þ diastolic pressure). Data are presented as mean AE SD. Results were compared with paired t-tests. The com...

Korotkoff sounds can be enhanced by elevating the arm overhead for 30 s before inflating the cuff, and then bringing the arm to the usual position to continue in the blood pressure measurement. This manoeuvre leads to louder systolic Korotkoff sounds and does not have an effect on measured blood pressure levels.

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