Article
The effect of clothes on blood pressure measurements
Blutdruckmessung mit bekleidetem und unbekleidetem Arm: kein Unterschied
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Published: | August 10, 2005 |
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Aim: One fact blood pressure measuring techniques is nearly completely neglected: What effect does clothing have on the readings? We determined the effect of wearing clothes under the manometer's cuff on blood pressure in manual and automatic blood pressure measurement.
Methods: 201 subjects (54 with arterial hypertension) were examined with the auscultatory sphygmomanometric (SPH) and the automatic oscillometric method (OSC), each with and without sleeved arm in random order. The auscultatory readings were blinded for the subjects' state of clothing. Common shirts and sweaters (< 2 mm) were used.
Results: Based on confidence intervals of the differences between sleeved and non-sleeved arm measurements and equivalence test sleeves did not lead to statistically significant effects. Evaluation was conducted with 95% confidence intervals (CI) for the averaged differences of the individual blood pressure readings. On average, in SPH sleeve effects led to an overestimation of 1.0 mmHg in SYS and of 0.8 mmHg in DIA. 95% CI were [-0.2;+2.1] for the systoles and [-0.1;+1.7] for the diastoles. In OSC sleeved measurements also showed a slight tendency towards overestimation. They were 1.1 mmHg (SYS) and 0.5 mmHg (DIA) higher in the average. 95% CIs were [-0.2;+2.4] in OSC SYS and [-0.4;+1.4] in OSC DIA. Neither in SPH nor in OSC significant differences could be determined. Measurements with and without sleeve can be accepted equal within an a priori defined interval of equivalence of ±4 mmHg.
Discussion: This study shows that measuring blood pressure with the manometer's cuff over the subject's sleeve does not differ significantly from non-sleeved arm measurements. This is true for a sample that includes normotensive as well as hypertensive persons with a wide age range. For clinical practice the not significant mean differences of 0.5 to 1.1 mmHg are interpreted as not relevant.