Comparison Between Automated and Manual Sphygmomanometer for Measuring Blood Pressure in Children

Address for correspondence: Dr. Amar M Taksande, Professor Department of Paediatrics Jawaharlal Nehru Medical College, Sawangi Meghe, Wardha, Maharashtra 442102, India E mail: amar.taksande@gmail.com Tel No: +917152-27705 1Dr. Amar Taksande, MD, FIAE, Fellow in Paediatric Cardiology, Professor, 2Dr. Aishwarya Jadhav, MBBS, Senior Resident, 3Dr. Jayant Vagha, Professor and Head of department. All from the department of Paediatrics, Jawaharlal Nehru Medical College, Sawangi Meghe, Wardha, Maharashtra, India. Abstract


Introduction
Blood pressure (BP) is seen as one of the vital signs of life.An accurate assessment of BP is very important for the diagnosis and treatment of hypertension.BP measurement can be taken by both invasively and non-invasively, but it requires careful a en on and dependent on proper use of the equipment.Hypertension is the most common risk factor for cardiovascular disease, accurate BP measurement is essen al in providing healthcare to decrease the risks of cardiovascular morbidity and mortality 1 .The importance of a aining the diagnosis of high BP and its con nuous monitoring are well known.Therefore, several equipments have been available for the measurement of BP, not only to be used by specialized individuals, but also by the popula on itself 2 .Although digital monitors are easier to use when compared to the mercury sphygmomanometers, it is essen al to establish their reliability and validity.Tradi onally, BP have been measured using a manual mercury sphygmomanometer, but in recent years the use of automated BP machines such as the Dinamap and Omron have been the trend in most hospitals 3 .However, many health workers ques on the accuracy and reliability of the automated machines when used in the clinical se ng, and s ll prefer the manual sphygmomanometer which is considered the 'gold standard'when used by a trained observer 4,5,6 .There is some evidence in the literature that digital monitors are reliable and accurate when compared with other devices, such as the aneroid or mercury devices 6,7,8,9 .This type of equipment can replace the manual sphygmomanometer in some contexts, such as at home or in epidemiological studies within the community.However, most studies were done only on adults, and therefore, the reliability of automated blood pressure machines among children's is unclear.This study was done to compare the blood pressure measurement measured by an Automated and Manual Sphygmomanometer in children and to determine the reliability of automa c BP machine for measuring the BP.

Material and Methods
This cross-sec onal study study was conducted in the paediatric department at Acharya Vinoba Bhave Rural Hospital which is a rural medical college located in Sawing, Maharashtra from September 2013 to March 2014.Inclusion criteria: Children were age 3-15 years and no known history of serious illness.Exclusion criteria: Upper limb amputa on, cuts or bruising of the skin at measurement sites, arrhythmia, aor c coarcta on, aor c dissec on, peripheral vascular disease, congenital heart disease and vasculi s.BP measurements were taken by postgraduate student in paediatrics using:-1.The manual device which was used is a standard mercury sphygmomanometer (M) with an appropriate cuff and Li man Classic II stethoscope.

The automated device (A) which was used is
the OMRON machine with diff erent size of cuff s [HEM-CS24 17-22cm (7-9inch) & HEM-CR24 22-32 cm (9-13inch)] 3. All machines which were used in the study were calibrated and checked for compliance to machine standards by the Biomedical Engineering Department of the Hospital.
Measurement of Blood Pressure: Children were posi oned supine, with arms straight and legs uncrossed.Appropriate size of the cuff was selected by measuring mid arm circumference at the halfway point between shoulder p and elbow p.A er that, we fi ed the cuff to the pa ent's arm.a.By Mercury sphygmomanometer (M): Firstly, we determined a 'systolic es mate' of the children BP by infl a ng the cuff un l the radial pulse can no longer be palpated.Then, again infl ate the cuff a further 30 mmHg and release the valve at 2 mmHg per second un l the radial pulse reappears.We recorded this reading as the systolic BP es mate.
b. Again we infl ated the cuff to 30 mmHg higher than the 'systolic es mate' and then slowly defl ated the cuff at 2 mmHg per second and, using a stethoscope, record measures corresponding to the 1 st and 5th Korotkoff sounds. 1 st Korotkoff sound was considered as systolic BP and 5 th Korotkoff sound was considered as diastolic BP.If Korotkoff sounds persist, the measurement was repeated with less pressure on the stethoscope head.If the sounds persist at low intensity, then K4 (muffl ing of sounds) was recorded as the diastolic pressure.
c.By Automa c blood pressure machine (A): The Omron HEM-7121 automa c measurements are based on smart ''infl ate'' technology (IntelliSense), where infl a on is driven by a pumping system and defl a on is driven by an electromagne c control valve that allows rapid air release.We pressed 'start' bu on on machine to commence BP measurement.Record was digitally displayed as systolic and diastolic BP.
Frequency of BP Measurement: For each person, the average of the two measurements were calculated from the two devices, which was leads to four readings per subject denoted as systolic manual, systolic automated, diastolic manual, and diastolic automated.Half of the BP was measured fi rst with the digital and subsequently with the mercury one, whereas the remaining half was evaluated in the opposite order.Heart rate was also obtained.There was a two minutes break between automa c and manual BP readings.
To detect a mean diff erence between measurement techniques of 5 mmHg (10%) at a two tailed alpha of 0.05, power of 80% the es mated sample size of 96 was required.
Sta s cal Analysis: SPSS-14 so ware was used for the sta s cal analysis.Means and standard devia ons of manual and automated systolic and diastolic BP values were calculated.A paired t-test was used to assess the diff erences between the manual BP and automated BP readings.Pearson's correla on coeffi cient was used to determine the rela onship between BP's measured by manual and automated BP device.Bland-Altman plots were used to show the distribu on of the diff erences between the methods at all pressures and the mean and standard devia on of the diff erences.A linear regression analysis was performed to examine the rela onship between the automated and manual BP readings with the automated systolic and diastolic BPs as the independent variables.The research was approved by an Ins tu onal Ethics Commi ee (IEC) and informed consent was obtained from the parents.

Results
Out of the 100 children studied, 48 were boys and 52 were girls.The age distribu on ranged from 5-15 years.Mean age of boys and girls were 10.04 ± 2.94 and 9.85 ± 3.04 years, respec vely.Mean weight was 27.16 ± 8.96, mean height was 129.60 ± 17.09 cm and mean circumference of arm was 18.01 ± 1.72 cm (range 15-22 cm).BP taken with the automated OMRAN device was systolic 109.77± 9.97 and diastolic 74.50 ± 8.32 mm Hg compared to systolic 112.68 ± 9.98 and diastolic 77.38 ± 7.91 mm Hg measured by manual mercury sphygmomanometer BP readings (p < 0.001).The comparison of the manual versus the automated readings showed a high coeffi cient of correla on (r2) for systolic BP (r2 = 0.80) and diastolic BP (r2 = 0.76) readings.
Bland-Altman plot (Fig. 1 and 2) demonstrates the mean diff erence between systolic and diastolic blood pressure measured by Mercury Sphygmomanometer and automated BP device (OMRON).Black line is the mean of the diff erences; do ed lines are both lower and upper 95% confi dence interval.If the diff erences within mean ± 1.96 SD are not clinically important, the two methods may be used interchangeably.
Linear regression analysis (Fig. 3) showed that the automated systolic BP is a signifi cant predictor (β = 0.897, p < 0.001) of manual systolic BP with a regression equa on (systolic BP = 14.11+ 0.89 × automated systolic).Also, Automated diastolic BP was also a signifi cant predictor (β = 0.829, p < 0.001) of manual diastolic BP with a regression equa on (Diastolic BP = 15.59 + 0.82 × automated diastolic).A linear regression analysis was performed to examine the rela onship between the automated and manual blood pressure (BP) readings with the automated systolic and diastolic BP as the independent variables.

Discussion
The prevalence of systemic hypertension in childhood is 1-2% in the developed countries.Similar data is lacking from India, small surveys in school children suggest a prevalence ranging from 2-5%.Norma ve values for BP are based on Mercury sphygmomanometer, which con nues to be the preferred method for BP es ma on.It is recommended that BP devices be calibrated and validated regularly.The oscillometric devices are increasingly used in infants (in whom ausculta on is diffi cult) and in intensive care se ngs when frequent BP measurements are needed.However, most oscillometric devices are not validated for children and their norma ve data based are not available 1,2,3,4 .In the literature, there is considerable debate in the accuracy of automated BP machines 5,6,7,8 .However, the level of agreement between automated and manual BP measurements can vary for systolic and diastolic readings, and in rela on to type of machine and pa ent popula on.
The study done by Sigurdsson JA et al 9 found that the agreement between the automa c BP and the conven onal mercury sphygmomanometer in adult is unsa sfactory for clinical purposes and therefore the methods are not interchangeable.Shibata K et al 10 concluded that the reproducibility of BP measured with mercury sphygmomanometer was less than 4%, with each Digital sphygmomanometer less than 9%.In another study, Rotch AL et al 11 reported that compared with the mercury sphygmomanometer, the automa c monitor was the most accurate in measuring.Menezes AM et al 12 reported the digital device showed a high level of agreement with the mercury manometer when measuring systolic BP.The level of agreement was lower for diastolic BP.In our study, we found high level of agreement between BP measured by manual mercury sphygmomanometer and automated devices.Previous studies 13,14,15,16 comparing the Omron (automated) device with mercury consistently showed lower readings of Omron (automated ) for both systolic and diastolic BP.The Ostchega Y et al 17 reported that the Omron (automated) and mercury device measurements were correlated (r = 0.92 for systolic BP and r = 0.79 for diastolic BP), same fi nding was found in our study also (r = 0.89 for systolic BP and r = 0.82 for diastolic BP).

Conclusion
This study concludes that the automated blood pressure device is reliable and accurate for measuring the BP in children.Also, we can use this device in the paediatric Out pa ents department (OPD) and In pa ents department (IPD) as there is no risk of mercury leakage and also reduces individual diff erences in measurement methods (human error).

Fig 1 :Fig 2 :
Fig 1: Bland and Altman plot showing diff erence of systolic BP (SBP) between mercury sphygmomanometer and automated device.
Fig 3:A linear regression analysis was performed to examine the rela onship between the automated and manual blood pressure (BP) readings with the automated systolic and diastolic BP as the independent variables.