ISSN: 2249-3905 COMPARISON BETWEEN PERFORMANCE OF ...

IJREAS

Volume 2, Issue 2 (February 2012)

ISSN: 2249-3905

COMPARISON BETWEEN PERFORMANCE OF STANDARD MERCURY AND OMRON HEM-4021 SPHYGMOMANOMETER IN A RESEARCH SETTING Gurmanik Kaur* Ajat Shatru Arora** Vijender Kumar Jain**

ABSTRACT The mercury sphygmomanometer, the “gold” standard for blood pressure (BP) measurements, has been gradually phased out in clinical and research settings because of environmental concerns. The rapidly increasing number of automated devices and the necessity of replacing the mercury sphygmomanometer have raised the concerns about the accuracy of BP monitors. Our on-going research compared the performance of standard mercury and OMRON HEM-4021, semi-automated sphygmomanometer, before implementing a study-wide transition to the semi-automated sphygmomanometer. BP of 50 normal and 24 hypertensive individuals was measured in random order, under standardized conditions, using both types of devices. The study found no statistically significant difference between systolic BP (SBP) and diastolic BP (DBP) of normal and hypertensive subjects. Regression analysis demonstrated that both devices have positive and statistically strong correlation between SBP and DBP measurements. Bland-Altman plot showed a perfect agreement between measurements of both devices for normal and hypertensive subjects. Mercury BP measurements can

be replaced

by

readings taken

using

OMRON

HEM-4021

sphygmomanometer in research settings. The slightly lower readings obtained with the OMRON HEM-4021 sphygmomanometer (in the context of reduced observer-subject interaction) may be a more accurate estimate of BP status. Keywords: Blood Pressure, Blood Pressure Determination, Mercury Sphygmomanometer, Semi-Automated Sphygmomanometer.

*Research Scholar, Electrical and Instrumentation Engineering Department, Sant Longowal Institute of Engineering & Technology, Longowal, Sangrur, Punjab, India. **Professor, Electrical and Instrumentation Engineering Department, Sant Longowal Institute of Engineering & Technology, Longowal, Sangrur, Punjab, India. International Journal of Research in Engineering & Applied Sciences http://www.euroasiapub.org

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INTRODUCTION The conventional approach to BP measurement is based on the use of the standard mercury sphygmomanometer, which has been regarded as the “gold standard” for BP measurements since its first description in 1896 [1, 2]. Many institutions began switching from mercury to non- mercury sphygmomanometers, due to the environmental concerns about the disposal of mercury contaminated medical waste and the risk of spills from them [3-6]. The international entities British Hypertension Society (BHS) [7], the association for the Advancement of Medical Instrumentation (AAMI) [8] and European society of hypertension (ESH) have established criteria for allowing the validation of these devices. Many devices available in the market have failed to fulfil the requirements of the three international entities [9-16]. However, the fact that a device passed a validation test does not mean that it will provide accurate readings in all subjects. For this reason, American Heart Association (AHA) has recommended that each automated sphygmomanometer should be validated on each subject before the readings are accepted [17]. The objective of this study is to test whether the semi-automated sphygmomanometer, OMRON HEM-4021 could provide the same high quality measurements as a standard mercury sphygmomanometer.

1. MATERIAL AND METHODS A. Subject Population This study involved 50 normal and 24 hypertensive subjects of SLIET campus. The subjects were randomly selected for enrollment in the study and were contacted by personal meeting. All gave consent to the study. B. BP Measurement The study was conducted over a period of two months. A specially separated room was organized to conduct the study. This ensured minimal interference within the room while the tests were being carried out. The observers involved in the study were trained using the BHS BP measurement training materials [18]. BP was measured on the same arm of each subject using the test and standard devices sequentially. Subjects remain seated with the back supported and left arm at heart level. The left arm circumference was measured and appropriate cuff size was used accordingly. The subjects were allowed to rest for 5 minutes before the first reading was taken; this was then discarded. Three more readings were taken, International Journal of Research in Engineering & Applied Sciences http://www.euroasiapub.org

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each 1 minute apart and the mean value was recorded for each individual. There was a 2minute break between the BP readings. All measurements were obtained under similar conditions except for the different BP recording devices [19, 20]. C. Data Analysis Data were expressed as mean±SD. A paired t-test was used to assess the differences between the manual and automated BP readings. A linear regression analysis was performed to examine the relationship between the automated and manual BP readings with the automated systolic and diastolic BP values. Bland-Altman plot was used to determine the agreement between measurements. All data was analyzed using MedCalc version 12.1.3.0.

2. RESULTS Socio-demographic characteristics of the participants are presented in Table I. TABLE I. Characteristics

CHARACTERISTICS OF PARTICIPANTS a

Normal

a

Hypertensive

(Number, N = 50)

(Number, N = 24)

Age (years)

23.1 ± 1.2 (21-28)

50.5±11.3 (28-80)

Height (m)

1.6±0.04(1.43-1.67)

1.6±0.1 (1.51-1.83)

Weight (kgs)

55.2±7 (39-70.9)

73.6±9.5 (50.3-92)

BMI (kg/m2 )

21.5±2.4 (15.1-26.3)

27.07±2.2(21.530.4)

27.5±0.5 (22-31)

29.1±1.8 (24.5-31)

Arm Circumference (cm) a.

Data were expressed as mean±SD (Range)

Mean value of BP (systolic/diastolic) taken with the OMRON HEM-4021 semi automated device was 104.5/66.9 compared to 104.7/67.2 with the standard mercury device for normal and 110.3/67.1 compared to 110.6/67.2 for hypertensive subjects. The results of paired t-test were demonstrated in Table II. We found no statistically significant difference between systolic BP (SBP) and diastolic BP (DBP) of normal and hypertensive subjects, as p > 0.05.

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TABLE II.

COMPARATIVE PERFORMANCE OF TWO D EVICES USING PAIRED T-TEST Subjects

b

b

Normal

0.17 ± 0.63 / 0.3 ± 1.11 0.06 / 0.06

Mean difference±SD

p

Hypertensive 0.2 ± 0.5 / 0.1 ± 0.8 b.

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0.06 / 0.4

All readings (systolic/diastolic) expressed in mmHg

Linear regression analysis showed that automated BP is significant predictor (p < 0.001) of manual BP readings for normal and hypertensive subjects as shown in Table III. Figure 1 and Figure 2 showed the relationship between manual BP readings and those measured with automated sphygmomanometer tested of normal and hypertensive subjects.

TABLE III.

Comparative Performance of Two Devices using Linear Regression

Analysis Subjects

Regression Equation

c

R

c

R2

c

p

Normal

y=2.7088+0.972x / y=1.3366+0.9757x

0.98/0.92 0.97/0.85