Journal of Human Hypertension (1999) 13, 105–109 1999 Stockton Press. All rights reserved 0950-9240/99 $12.00 http://www.stockton-press.co.uk/jhh ORIGINAL ARTICLE Arm position is important for blood pressure measurement RT Netea, JWM Lenders, P Smits and T Thien Department of Internal Medicine, University Hospital Nijmegen, The Netherlands Aim: To test the effect of positioning the arm on the arm- nificantly higher (P Ͻ 0.0001) when the arm was placed rest of a common chair, below the officially rec- on the arm-rest of the chair than at the right atrial level. ommended right atrial level, on the blood pressure (BP) The same differences ± s.d. in BP between the two pos- readings in a group of out-patients. itions were obtained with both measurement tech- Patients and methods: A group of 69 patients (58 hyper- niques: 9.7 ± 9.4 mm Hg (systolic) and 10.8 ± 5.8 mm Hg tensives; 39 males; mean ± s.d. age 54.1 ± 16.0 years) (diastolic) with the mercury sphygmomanometer and participated in the present study. BP and heart rate respectively 7.3 ± 8.9 mm Hg and 8.3 ± 6.0 mm Hg with values obtained in each of the following two positions the oscillometric device. No difference in the heart rate were compared: (1) sitting with the arms supported on was found between the two positions. the arm-rests of the chair and (2) sitting with the arms Conclusions: Placing the patient’s arms on the arm-rest supported at the level of the mid-sternum (the approxi- of the chair instead of at the reference right atrial level, mation of the right atrial level). BP was measured simul- BP measurement will result in spuriously elevated BP taneously at both arms, with a mercury sphygmoman- values. This may be of great importance for the diag- ometer at the right arm and with an automatic nosis and the subsequent treatment decisions for oscillometric device at the left arm. patients with hypertension. Results: Both the systolic and diastolic BPs were sig- Keywords: blood pressure measurement; arm position Introduction rest of a common chair. The aim of the present study was to examine the effect of such a deviation from The diagnosis and treatment of hypertension is the recommended position on the BP readings in a mostly based on the indirect blood pressure (BP) group of out-patients. The indirect BP readings measurement. Therefore this clinical procedure can taken in two positions were compared: (1) seated have far-reaching consequences. One of the most with the arms supported at the level of the right important factors that affects the BP measurement is atrium and (2) seated with the arms supported on the patient’s position in which the BP is measured. the arm-rests of a common chair. The reference point for the measurement of BP is the right atrium,1 the so called heart level. Recent guidelines recommend that the arm should be Patients and methods placed at the ‘heart level’ during BP measurement, A group of 69 out-patients (30 females; 39 males; irrespective of the body position.2–6 However, it is mean ± s.d. age 54.1 ± 16.0) years; body mass index only vaguely suggested how the ‘heart level’ can be 26.7 ± 4.1 kg/m2; right arm circumference 29.5 ± practically estimated. Moreover it is not always indi- 2.7 cm; left arm circumference 29.2 ± 2.7 cm) partici- cated which anatomical segment of the arm should pated to our study. Fifty-eight of them were hyper- be at heart level.4–6 tensives and out of these 43 were taking antihyper- Previous studies have shown large differences in tensive medication at the time when they were the sitting BP between readings taken with the arm involved in the study. Patients with diabetes mel- at the heart level and with the arm vertically pen- litus, pregnancy, heart failure, autonomic neuro- dent by the patient’s side.7–11 However, in daily pathy or those taking ␣-adrenoceptor blockers or tri- practice as well as in research the arm position dur- cyclic antidepressants were excluded from the ing BP measurement is often neglected.12,13 As a present study. deviation from the recommended position, the BP is All the subjects were familiar with the measure- often measured by having the patient seated with ment of BP and a detailed explanation of the pro- the forearm supported on the desk or on the arm- cedure was given to the subjects before starting the measurements. Speaking with the subjects was avoided during both the resting time and the Correspondence: Professor Theo Thien, Department of Internal measurements. Medicine, University Hospital Nijmegen, Geert Grooteplein 8, 6500 HB Nijmegen, The Netherlands The whole procedure was carried out in a quiet Received 16 April 1998; revised 10 August 1998; accepted 17 room, at a comfortable temperature (21–23°C), by a August 1998 single trained observer (RTN). The right atrium level Blood pressure measurement and arm position RT Netea 106 was located according to British Hypertension Table 1 Systolic and diastolic BPs (mm Hg) and heart rate Society recommendations5 at the level of mid-ster- (beats/min) in 69 volunteers with the arm at right atrial level (arm up) and on the arm-rest of the chair (arm low). Results are given num (precisely determined in each subject at half- as mean ± s.e. way between manubrium at fossa jugularis and xyphoid at fossa epigastrica). In all subjects the BP Right arm Left arm was measured after 5 min of rest sitting in a comfort- (sphygmomanometer) (oscillometric) able ordinary chair with the back supported and the feet on the floor. Three BP readings 1-min apart were Systolic blood pressure taken, the patients having their arms supported arm up 133.3 ± 2.5 131.8 ± 2.3 arm low 143.0 ± 2.4 138.9 ± 2.5 passively at each of the two levels: the level of the difference 9.7 ± 1.1* 7.3 ± 1.0* arm-rest of the chair and with the cubital fossa at the level of mid-sternum.13 The sequence of the pos- Diastolic blood pressure itions was randomised. Two minutes of pause were arm up 77.7 ± 1.2 78.0 ± 1.2 ± ± allowed between the last reading in the first position arm low 88.6 1.1 86.2 1.2 difference 10.8 ± 0.7* 8.3 ± 0.7* and the first reading in the second position. The BP was measured simultaneously at both arms using a Heart rate Hawksley random-zero sphygmomanometer arm up 66.2 ± 1.3 66.0 ± 1.3 × arm low 66.7 ± 1.3 66.1 ± 1.3 (bladder size 36 13 cm) together with a Rappaport ± ± Sprague stethoscope at the right arm and an auto- difference 0.5 0.3 0.1 1.1 matic oscillometric device (Bosomat) (bladder size P Ͻ 0.0001 for arm low vs arm up. 22 × 12.5 cm), previously tested for accuracy,14 at the left arm. With the random-zero sphygmoman- ometer, phase I of Korotkoff sounds was used to Table 2 Systolic and diastolic BP values (mm Hg) and the differ- determine the systolic BP and phase V for the dia- ence (mm Hg) between the readings with the arm on the arm-rest of the chair (low) and with the arm at right atrial level (up) in the stolic BP to the nearest 2 mm Hg, with a maximal ± deflation rate of 2 mm Hg/sec. Corrected BP values two sequences of these positions. Results are given as mean s.e. for random zero readings were calculated after all Sequence low/up Sequence up/low measurements were done. After each BP reading a (n = 34 subjects) (n = 35 subjects) 20-sec pulse rate was counted at the right radial artery. The automatic device also registered the systolic diastolic systolic diastolic heart rate. Finally, each subjects body weight, height and arm circumference (halfway between the acro- Right mion and olecranon) were determined. (sphygmomanometer) The three readings taken in each position were arm up 135.5 ± 3.9 78.2 ± 1.8 131.2 ± 3.4 77.3 ± 1.7 arm low 148.3 ± 3.9 90.2 ± 1.8 137.9 ± 2.7 87.1 ± 1.5 averaged to obtain a representative BP for that pos- difference 12.9 ± 1.5**11.9 ± 0.7** 6.7 ± 1.5** 9.8 ± 1.2** ition. Student’s t-test was used to test for differences in BP and heart rate between the two positions. Left Spearman’s rank correlations were computed (oscillometric) ± ± ± ± between the individual differences obtained with arm up 133.5 3.7 78.1 1.8 129.8 3.0 77.6 1.6 arm low 144.6 ± 3.9 89.0 ± 1.8 133.4 ± 2.9 83.5 ± 1.7 the two measurement techniques with respect to the difference 11.1 ± 1.6**10.8 ± 1.1** 3.6 ± 1.2* 5.8 ± 0.8** systolic and diastolic BPs. The statistical signifi- Ͻ cance was reached when P 0.05 (two-sided). *P Ͻ 0.01; **P Ͻ 0.001. Results were significantly lower when the patient’s arms Both systolic and diastolic BPs were significantly were placed at the right atrial level than when the higher (P Ͻ 0.001) when the arm was placed on the arms were on the arm-rests of the chair. For both arm-rest of the chair (Table 1). This was the case systolic and diastolic BPs, the differences between for both arms.