Bigger Biceps Lead to Higher Blood Pressure Readings

Abstract

The position of both the body and the arm during indirect blood pressure (BP) measurement is ofttimes neglected. The aim of the present study was to test the influence of the position of the patient on BP readings: (1) sitting with the arms supported precisely at the right atrium level and (two) supine: (a) with the arms precisely at the right atrium level and (b) with the artillery on the exam bed. In a first group of 57 hypertensive patients, 2 sessions of BP and eye rate (Hour) measurements were performed in two positions: sitting and supine with the artillery supported precisely at right atrium level in both positions. BP was measured simultaneously at both arms, with a Hawksley Random Zippo sphygmomanometer at the correct arm, and with an automated oscillometric device (Bosomat) at the left arm. BP and Hr readings obtained in the two positions were then compared. In a second group of 25 normo- and hypertensive persons, ii sessions of BP and Hr readings were performed in supine with the arms in ii different arm positions: (a) the arm placed precisely at right atrium level and (b) the other arm on the exam bed. The measurements were performed at both artillery with 2 automated devices (Bosomat). The readings taken in the two positions were compared. Both systolic BP (SBP; by ix.5±9.0 (standard deviation, southward.d.); right arm) and diastolic BP (DBP; by 4.8±6.0 mmHg; right arm) were significantly higher in the supine than in the sitting position. When the ii different arm positions (torso continously supine) were compared in the 2d part of the study, significantly higher SBP (by 4.half dozen±6.1 mmHg) and DBP (by 3.9±ii.eight mmHg) were obtained when the arm of the patient was placed on the bed (beneath the right atrium level), than when the arm was placed at the level of the right atrium. BP readings in sitting and supine positions are not the same. When according to guidelines the arm of the patient is meticulously placed at the correct atrium level in both positions, the difference is even greater than when the arm rests on the desk-bound or on the arm support of the chair. Moreover, in the supine position small but significant differences in BP are measured between arm on a 5 cm-high pillow and arm on the bed. In every study reporting BP values, the position of both the torso and particularly the arm should be precisely mentioned.

Introduction

The indirect blood pressure (BP) measurement with a mercury or aneroid sphygmomanometer and a stethoscope past a trained observer is widely recommended as the cheapest and the most accurate manner of measuring the BP in the daily routine. The position of the patient during the measurement is often neglected. The reference point for the measurement of BP is the correct atrium, the then-chosen 'middle level'.^one The guidelines of the Globe Health Organisation/International Social club of Hypertension (WHO/ISH) recommend that the BP should be routinely measured with the patient comfortably seated with the arms supported at centre level.² To detect orthostatic hypotension, BP should also exist measured with the patient commencement supine and subsequently in the standing position.² It has been suggested that BP readings taken in sitting and supine positions can be considered equivalent if the patient'south arm is placed at eye level (right atrium) in both positions.³ As a practical approximation of the centre level when sitting or standing, it has been proposed to take the level of the quaternary intercostal space² or the level of the midsternum.ⁱⁱⁱ We could find but scarce information about the approximation of the heart level in the supine position. Using computerised tomography, it has previously been shown that the level of the right atrium in the supine position is situated approximately half way between bed surface and sternum.⁴ A special pillow has been adult to be placed under the arm, in order to support information technology at the right atrium level in the supine position.^iv This pillow is however non available in most hospitals. For practical reasons, positioning the arm of the patient on the bed has been recommended every bit adequate during BP measurement in the supine position.^five

The showtime aim of the present study was to test the influence of body posture on the indirectly measured BP values when the arm was placed at the right atrium level. The second aim of our study was to examination the effect of the level of the arm on the indirectly measured BP values in the supine position: arm on the bed surface and arm at half distance betwixt the sternum and the bed.

Patients and methods

Influence of torso position on BP readings

A total of 57 hypertensive patients (29 males, mean historic period 55±12 (s.d.) years, BMI 25.7±four.4 (southward.d.) kg/m^two, arm circumference right 29.two±3.3 (due south.d.) cm and left 28.9±3.3 (south.d.) cm) participated in this part of the study. Of these, 50 patients were on antihypertensive drug treatment. Two sessions of BP measurements, separated by a x min pause, were performed in two positions: (1) lying on a bed with the arms supported with the palms upwards and both the cubital fossa and the upper arm at halfway betwixt the bed and the sternum^four and (2) sitting on a chair with the arms supported horizontally with the palms upward and over again both the cubital fossa and the upper arm at the level of the midsternum. The arm was placed at the approximated right atrium level using a levelling instrument. Each session (at random beginning sitting or supine) started with v min remainder in the respective position. Then BP recordings were taken in triplicate ane min apart, simultaneously at both arms, using a Hawksley random-cipher sphygmomanometer (Hawksley and Sons, Lancing, Britain; float size 36 × thirteen cm) and a stethoscope at the right arm and an automatic oscillometric device (Bosomat; Boso oscillomat, Bosch, Jungingen, Germany; bladder size 28 × 12.v cm)^half-dozen at the left arm. In betwixt, a 20 s middle rate (Hr) was counted at the right radial artery.

Influence of arm position on supine BP readings

In all, 25 subjects (16 hypertensive patients, 11 males, mean historic period 52.9±16. 5 (s.d.) years, BMI 26.1±4.9 (south.d.) kg/m², arm circumference correct 29.5±0.7 (south.d.) cm and left 29.3±one.two (due south.d.) cm) participated in the report. Pregnant women, patients with BP differences between the ii arms larger than 10 mmHg and patients with arm circumferences larger than 35 cm were excluded. The BP measurements were performed using ii automatic oscillometric devices (Bosomat; Boso oscillomat, Bosch, Jungingen, Frg; float size 28 × 12.5 cm). All BP readings were taken simultaneously at both arms, with the subject comfortably supine on an examination bed with 1 small absorber nether the head. To examination for BP differences between the 2 arms, i BP reading was get-go performed with the patients in the described supine position and both arms placed on the bed, with the palms upward. One arm (at random right or left) was then supported with a specially designed pillow with the cubital fossa and upper arm at half-distance between the bed and the sternum (approximation of the right atrium level), whereas the other arm remained on the bed (Figure 1). Later on 5 min of remainder, iii BP and HR were measured, 1 min apart. The arm position was switched thereafter, with the arm offset supported on the pillow now being placed on the bed and vice versa. Again after 5 min of rest, the three BP and 60 minutes readings were repeated.

Figure 1

Computerised tomography illustrating the difference between the arm levels used in the present study (right arm supported at the right atrium level and left arm supported on the exam bed). R: correct arm; 50: left arm; RA: correct atrium.

Full size image

In both studies, all BP measurements were performed by the same trained observer (RTN), in a serenity room, with comfortable temperature. Every patient that agreed to participate in our study received detailed caption before the procedure commenced and talking was avoided during the measurements.

Statistical analysis

The hateful of iii readings of BP and Hour obtained, respectively, in each position was considered representative for that position. Paired t-examination was used to compare the differences between the BP and HR, respectively, in different positions. The test was considered statistically significant when P<0.05 (two sided). The results are expressed as mean±s.d. unless otherwise stated.

Results

Influence of body position on BP readings

The primary results are given in Table i. Both the systolic (SBP) and the diastolic (DBP) blood pressures were significantly college in the supine position regardless of the instrument used (P<0.001 for both). The HR was slightly, merely significantly, higher in the sitting than supine position (63.3±nine.0 vs 62.2±9.0 bpm respectively; P=0.037).

Tabular array 1 Systolic blood pressure (SBP), diastolic blood pressures (DBP) in mmHg, and centre rate (HR) in bpm, in the 57 patients in the sitting and supine positions. Results are given as means±s.d.

Full size table

Influence of arm position on supine BP readings

Table 2 presents the BP and HR readings taken in the supine position with the arm on the examination bed and with the arm supported at the right atrium level. As seen in Tabular array two, no divergence was found in the initial BP readings between the ii arms. Nevertheless, significantly college BP readings were recorded when the arm was placed on the bed than when the arm was supported at right atrium level. Statistical significance was not reached for the SBP in the right arm merely the tendency of the results was similar to that in the left arm. Irrespective of the arm position, the average BP in the offset attended position (afterwards the first 5 min of rest) was significantly lower than the initial BP (showtime BP). Except for a slightly higher SBP difference at the correct arm when the sequence of positions was arm loftier/arm low than arm depression/arm high (vii.0±4.3 mmHg vs 2.3±6.seven mmHg, P=0.048), no significant effect of the sequence of the two positions was detected on the BP differences. With respect to the 60 minutes, afterwards an initial small subtract in the commencement 5 min of residuum information technology remained unchanged during the procedure.

Table 2 Supine systolic (SBP), diastolic (DBP) claret pressure level in mmHg, and heart rate (Hour) readings in bpm, in 25 subjects with the artillery supported at the heart level and with the arms on the bed; the sequence of the two positions was randomized. Results are given as mean±s.d.

Full size tabular array

Discussion

In our group of hypertensive patients, in an outpatient setting, we found significantly lower BP readings in the sitting than in the supine position when the patient's arms were supported at the right atrium level as exactly as possible in both positions. This confirms previous observations in normo-tensive subjects.^4,7

The BP measurement in sitting position is well-nigh often used in the general doctor'south part, whereas in some hospitals BP is often measured in supine position. Both diagnostic and therapeutic decisions are based on BP readings taken sometimes in sitting and sometimes in supine positions, since they are frequently regarded equally equivalent. The differences we plant using the Hawksley Random Zero sphygmomanometer are sustained by those found with the automatic musical instrument. The explanation of the slight differences in results between the ii instruments could be the different measurement principle. One should realise that with the oscillometric method the mean arterial pressure is determined by the maximal amplitude of the oscillations, and SBP and DBP are afterward computed from this value. With the mercury sphygmomanometer, however, both SBP and DBP are separately measured.

Another gene that is oft neglected during BP measurement is the position of the arm of the patient. We and others^{seven,eight,ix} take shown that this induces a consequent difference between BP readings taken with the arm in dissimilar positions. In patients with a length of 190 cm, nosotros measured differences every bit big as 25 cm betwixt the level of the arm support of a common chair and the mid-sternum level. Such differences may result in big errors in BP readings that could obscure or even inverse the difference in BP readings between the sitting and supine position. The upshot of the arm position on BP readings in the supine position was especially observed during nocturnal BP registration in convalescent BP measurement (ABPM) studies^10,11,12,13 and in pregnant women,^14,15,16 when the BP was measured in the lateral recumbent position. The BP values recorded when the arm was placed above the heart level were significantly lower than those recorded when the arm was situated below the centre level. When the patient is lying on the examination bed, one assumes that the arms of the patient residue at the level of the correct atrium.^v However, Ljungvall et al ^iv demonstrate that even in this example the arms of the patient are situated conspicuously below the right atrium level. Our results in a grouping of patients with a broad range of BP values, show that even such a small variation in the arm position tin can issue in significant BP differences. To obtain a double command of the results and to avert observer bias, we used automated devices, and nosotros performed simultaneous readings in both arms and for each arm in both sequences of the two positions. The results showed like trends in both arms and were independent of the sequence of the two positions and of the BP level. The magnitude of differences we obtained was slightly smaller (ranging from 2.8 to 4.vi mmHg) than in the report of Ljungvall et al (5.5 mmHg). A possible explanation for the difference between these two studies could be the fact that oscillometric instruments were used in the present study, whereas standard mercury sphygmomanometers were used in the study of Ljungvall et al. ⁴ Nevertheless, the differences nosotros obtained are closer to those theoretically expected, when one considers the effects of hydrostatic forces as a major determinant of the differences in BP betwixt the two positions.¹⁷ Differences of iii–4 mmHg may be modest as absolute value, but are nonetheless important in epidemiological terms.

In conclusion, the present study shows that the assumption that blood pressure in sitting and supine position can be considered similar is wrong even when the arm of the patient is placed at the right correct atrium level in both positions, as officially recommended.

Supporting the arm of the patient on the arm back up of a mutual chair in the sitting position could partially correct and potentially reverse the differences betwixt sitting and supine positions. Nonetheless, this introduces a new source of variation in BP measurement: the various distances between the heart level and the arm support of the chair, which can be as large equally 25 cm in tall patients. In consequence, such practice is incorrect and should be discouraged.

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1. Sectionalisation of General Internal Medicine, Department of Medicine, University Hospital Nijmegen, Nijmegen, The Netherlands

   R T Netea, J W M Lenders, P Smits & Th Thien

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Correspondence to Th Thien.

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Netea, R., Lenders, J., Smits, P. et al. Both body and arm position significantly influence blood force per unit area measurement. J Hum Hypertens 17, 459–462 (2003). https://doi.org/10.1038/sj.jhh.1001573

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• Received: 28 September 2002

• Revised: 18 January 2003

• Accustomed: 18 March 2003

• Published: 24 June 2003

• Issue Date: 01 July 2003

• DOI : https://doi.org/10.1038/sj.jhh.1001573

Keywords

• blood pressure level measurements
• hypertension
• torso and arm position

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Source: https://www.nature.com/articles/1001573

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