|Year : 2019 | Volume
| Issue : 1 | Page : 69-73
Difference in forearm and upper arm blood pressure measurements in prenatal women
MCH Unit, CON-A, King Saud Bin Abdul-Aziz University for Health Sciences, King Abdul-Aziz Hospital, Ministry of National Guard Health Affairs, Al-Ahsa, Kingdom of Saudi Arabia
|Date of Web Publication||12-Jun-2019|
Dr. Thilagavathy Ganapathy
CON-A, King Saud Bin Abdul-Aziz University for Health Sciences, King Abdul-Aziz Hospital, Ministry of National Guard Health Affairs, P. O. Box: 2477, Al-Ahsa 31982
Kingdom of Saudi Arabia
Source of Support: None, Conflict of Interest: None
Background: In health-care services, when bare upper arm blood pressure (BP) measurement is impractical, the forearm may be used as a surrogate for traditional upper arm BP. Objective: This exploratory study aimed to determine the significant difference and correlation between the upper versus forearm BP measurements among low-risk prenatal women. SMaterials and Methods: A total of 156 low-risk prenatal women in the third trimester of pregnancy attending antenatal clinics at Municipal Maternity Corporation Hospitals, Bengaluru, were recruited by purposive sampling. Upper and forearm noninvasive BP (NIBP) measurements obtained by mercury sphygmomanometer, thrice at an interval of 15 min were averaged. The main outcome measures were the significant difference and correlation between the upper arm and forearm BP measurements. Results: The mean systolic BP (SBP) (117.14 ± 3.041 mmHg) and diastolic BP (DBP) (69.31 ± 8.461 mmHg) in the forearm was significantly higher than the upper arm SBP (111.72 ± 5.53; P = 0.002) and DBP (61.46 ± 6.014 mmHg; P = 0.016). The mean difference in SBP between upper and forearm was 5.42 ± 2.016 mmHg and in DBP 7.85 ± 3.204 mmHg. Upper versus forearm BP measurements had revealed a significant positive linear correlation in SBP (r = 0.849; P = 0.013) and DBP (r = 0.816; P = 0.021) by Pearson product-moment correlation coefficient. Clinically 94 (72.31%) had a significant BP measurements difference in forearm versus upper arm by approximately 6–10 mmHg. None of the maternal characteristics were independent predictors for the mean difference in SBP and DBP measurement. Conclusion: Forearm NIBP measurements are higher than the BP obtained at the upper arm location. This must be taken into consideration whenever the forearm is used as an alternative site for the upper arm BP.
Keywords: Blood pressure, forearm, pregnancy, upper arm
|How to cite this article:|
Ganapathy T. Difference in forearm and upper arm blood pressure measurements in prenatal women. Arch Med Health Sci 2019;7:69-73
| Introduction|| |
Accurate measurement of blood pressure (BP) in the prenatal period is vital to guide the health-care personnel for making appropriate clinical decisions in the diagnosis and management of pregnancy-induced hypertension. Hypertension in pregnancy is one of the major causes for maternal morbidity and mortality in low- and middle-income countries. Preeclampsia is the leading cause of iatrogenic preterm birth, stillbirths, and neonatal deaths in developing countries.
A Confidential Enquiries into Maternal Deaths report revealed that a lack of access to simple, easy to use BP instrument, and substandard maternal care was the most common reasons for maternal, fetal deaths secondary to pregnancy-induced hypertension. The report also argued that the majority of maternal deaths could have been prevented if early warning signs of impending eclampsia were recognized and treated on more promptly, by accurate BP measurement. Thus, the ability to measure BP accurately is an indispensable skill for health-care professionals regardless of setting, to promote safe maternal and childhood.
Perinatal guidelines outline standards for obtaining accurate and reproducible BP measurements among pregnant women. It recommends an initial inflation of the cuff by 20–30 mmHg above the palpable SBP, deflation at a rate of 2 mmHg/s, recording BP to the nearest 2 mmHg, and the use of Korotkoff Phase V to indicate DBP. These standards include guidelines for the correct-sized cuff for the patients to ensure accuracy. In a clinical setting, when standard cuffs are not available, using a large cuff in a woman with a normal arm circumference, BP can be underestimated. On the contrary, if a smaller cuff is used, when optimal cuffs are often less readily available, it can overestimate the readings in normotensive women. In a setting, where a standard BP cuff is not available or when the patient is obese, or with thick sleeves or when it is difficult to physically access the upper arm, the radial artery can be easily accessed as an alternative site, and the forearm BP can be used as a surrogate for the standard upper arm BP., Utilization of the radial artery at the forearm may be preferable to the brachial, due to the ease of access and less discomfort on cuff inflation. Whereas, it has been demonstrated that lack of knowledge to perform the measurement at alternative sites results in misdiagnosis, wasted efforts, time, and lack of professional nurse competency.
The differences between the measurements in the radial and brachial arteries are still insufficiently established in the literature, and no studies have been undertaken in India, which leaves the room for this research. Under these circumstances, this present study was conducted to find out the predictable correlation and significant difference between the upper versus forearm BP measurements obtained from the third trimester normotensive pregnant women to evaluate the practicality of forearm BP as a surrogate for the standard upper arm BP.
| Materials and Methods|| |
Following approval of the study protocol by Bruhat Bengaluru Mahanagara Palike (BBMP) -District Health and Family Welfare Officer (Maternal Child Health and Family Welfare) and Medical officer-in-charge of the selected Municipal Maternity Corporation Hospitals, Bengaluru, South Karnataka, the participants were recruited by purposive sampling technique. A low-risk normotensive primigravidae and multigravidae in the third trimester of pregnancy, attending antenatal clinic and ultrasound examination were included. Prenatal women with risk factors complicating pregnancy were excluded. Written informed consent was obtained and participants were informed about the study procedures in detail by the midwives responsible. The study followed the Declaration of Helsinki principles.
A pilot study was done among 15 prenatal women to determine the reliability and accuracy of the BP measurement. Using an optimal BP cuff for upper arm and pediatric cuff for forearm, BP were measured by a calibrated mercury sphygmomanometer and a Littman® Stethoscopes. The midwife was trained to inflate and deflate the bladder in the cuff gradually, see the manometer and the meniscus of the column of the mercury, palpate the brachial artery, and place the cuff, so that the midline of the bladder is over the arterial pulsation, wrap and secure the cuff snugly around the client's bare upper arm, hear the Korotkoff sounds, differentiating them from extraneous noises, make a note of the pressure on the manometer at the first appearance of sound (Phase I) and the muffling sound (Phase IV), and when they disappear (Phase V) to the nearest 2 mmHg. Interrater reliability was established between the two midwives (r = 0.89). The main outcome measures were the significant difference and correlation between upper arm and forearm systolic and DBP measurements. Midarm circumference was measured at the midpoint of acromium and olecranon process, and the forearm between the midpoint of the olecranon and the styloid process of the ulna and radius. All BP measurements were taken with women seated on a chair, legs uncrossed, and bare arm resting on a standard table at the level of the heart. Women were instructed to refrain from talking, laughing during the BP measurement. The site that to be measured first was decided randomly and the measurements were repeated thrice at an interval of 15 min to obtain reliable readings. In both the brachial and radial BP measurements, SBP was recorded at the first and DBP at the fifth Korotkoff sound. Both the SBP and DBP measurements were recorded to the nearest 2 mmHg. The three pairs of readings were averaged to obtain mean SBP and DBP.
A statistical power analysis was performed for sample size estimation, based on data from the previous study. With an alpha = 0.05 and power = 0.80, at 95% confidence interval (CI) to detect the differences in upper and forearm BP measurements, the projected sample size needed was 120 women. Taking into consideration for the missing data and noncompliance by 30%, 156 prenatal women were recruited.
Demographic data and SBP and DBP were analyzed by descriptive statistics-mean and standard deviation (SD). Paired t-test was used to determine the difference between upper arm and forearm BP measurements. Pearson product-moment correlation was used to evaluate the correlation between mean BP measurements in the upper versus forearm. Chi-square or Fisher's exact probability was used to analyze the significant association between the maternal characteristics and the mean BP measurements in the arm. A significance level of P < 0.05 (two-tailed) was used for all analyses. Statistical analyses were performed using IBM SPSS Statistics (Version 21.0. IBM Corp., Armonk, NY, USA).
| Results|| |
Sociodemographic characteristics of prenatal women
Of the 156 prenatal women who agreed to participate in the study, 26 of them were excluded from the study as nine of them were noncompliant with the next two repeated measurements, seven had poor quality of Korotkoff sounds, and ten had missing values. Final analyses consisted of 130 prenatal women in the third trimester of pregnancy. The mean age of the prenatal women was 25.41 ± 2.927 ranging from 21 to 32 years. Of them, 64 (49.23%) were primigravidae and 66 (50.77%) were multigravidae, with the mean parity of 2.3 ± 0.436. The mean gestation in weeks was 32+5 ± 2.51, ranging from 25 to 40 weeks. All most, all of them 127 (97.69%) were literates, whereas a few 3 (2.31%) did not have formal education. Majority were employed 112 (86.15%) and n = 18 (13.85%) were homemakers. Mean upper arm circumference was 27.9 ± 2.979 cm, ranging from 22.5 to 33.5 cm. Forearm mean circumference was 23.6 ± 2.701, ranging from 21 to 26 cm. The mean hemoglobin level was 13.47 ± 2.049 gm%; ranging from 10.8 to 14.65 gm% [Table 1].
Mean systolic blood pressure and diastolic blood pressure measurements in upper versus forearm
Among 130 prenatal women, 400 valid BP measurements were obtained on three repeated measurements by calibrated mercury sphygmomanometer. The mean SBP in the forearm (117.14 ± 3.041, ranging from 90 to 120 mmHg) was significantly higher than the upper arm (111.72 ± 5.531; ranging from 88 to 118 mmHg) “t”(129)=21.019; P = 0.002. Similar pattern of BP values was observed in DBP measurements in the forearm versus upper arm. The forearm DBP was significantly higher (69.31 ± 8.461 mmHg, ranging from 54 to 80 mmHg) than the upper arm (61.46 ± 6.014 mmHg, ranging from 50 to 78 mmHg) “t”(129)=34.041; P = 0.016 [Table 2].
|Table 2: Mean systolic blood pressure and diastolic blood pressure measurements in upper versus forearm (n=130)|
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Mean difference in systolic blood pressure and diastolic blood pressure readings in upper versus forearm
The mean difference in SBP between the upper and forearm was 5.42 ± 2.016 mmHg with the range of 2–8 mmHg. Conversely, mean difference in DBP also revealed the similar findings. The mean difference in DBP was 7.85 ± 3.204 mmHg, ranging from 0 to 10 mmHg. Clinically, 94 (72.31%) had a significant BP measurements differences in the forearm versus upper arm by approximately 2–10 mmHg [Table 3].
|Table 3: Mean difference in systolic blood pressure and diastolic blood pressure readings in upper versus forearm (n=130)|
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Correlation of blood pressure measurements in upper versus forearm
Pearson product-moment correlation coefficient between upper versus forearm had revealed a significant positive linear correlation in SBP (r = 0.849; P = 0.013) and DBP (r = 0.816; P = 0.021) [Table 4].
|Table 4: Correlation of blood pressure measurements in upper versus forearm (n=130)|
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Association of blood pressure measurements with maternal characteristics
Chi-square/Fisher's exact probability test revealed an insignificant association of maternal characteristics such as age (χ2 = 18.413; P = 0.461), parity (χ2 = 12.043; P = 0.139), employment status (χ2 = 18.023; P = 0.417), gestational age in weeks (χ2 = 22.913; P = 0.514), and hemoglobin level (χ2 = 11.051; P = 0.627) with mean difference in BP measurements between upper versus forearm [Table 5].
|Table 5: Association of blood pressure measurements with maternal characteristics (n=130)|
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| Discussion|| |
Small inaccuracies in BP measurements can have a significant consequence in prenatal women. It has been estimated that the untreated 5 mmHg of excessive SBP would increase the prevalence of myocardial infarctions and cerebrovascular accident among individuals with hypertension. On the contrary, overestimating true BP by 5 mmHg would lead to misdiagnosis, unpleasant experiences, medical procedures, psychological trauma, treatment with antihypertensive medications, exposure to adverse drug effects, and unnecessary financial burden. Therefore, the accuracy of BP measurements is highly critical in pregnancy, as it impacts maternal and perinatal clinical outcomes.
It is well-established and standard practice to measure noninvasive BP (NIBP) in the upper arm. However, there are times when it is either not ideal or not possible to use the upper arm for BP measurement. Researchers, reported that the forearm may be used as a viable alternative to the upper arm BP measurements. Although a number of previous studies have researched on the utility of forearm as an alternative site for the upper arm measurements of NIBP, few have reported conflicting results and most of the studies were focused on obese and hypertensive individuals. However, this research study had investigated the suitability of the forearm for NIBP measurements among low-risk prenatal women in the third trimester of pregnancy to draw relevant conclusions from the analyses. Our findings showed a statistically significant difference in mean SBP and DBP in the upper versus the forearm. Singer et al. concluded that wrist placement of BP cuff was an acceptable alternative to arm measurement involving 151 conveniently selected normotensive ambulatory individuals. Their findings showed that the mean forearm SBP (129.8 ± 20.7 mmHg vs. 126.2 ± 17.6 mmHg; P = 0.002) and DBP (80.7 ± 14.5 mmHg vs. 76.8 ± 13.4 mmHg (P < 0.001) had a good correlations 0.75 (P < 0.001) and 0.72 (P < 0.001).
Singer et al. concluded that forearm is a good predictor of upper arm BP measurements and may be when measurement of the upper arm BP is not feasible.
Li et al. attempted to find the relationship between BP measured on the brachial artery versus the radial artery in the right arm in 1890 valid pressure readings from 315 normotensive adults at Drum Tower Hospital. They found similar results of our study, findings showing that mean BP values in the upper arm being significantly lower than the forearm in both the systolic (127.9 ± 19.5 vs. 145.2 ± 22.7 mmHg) and DBP measurements (92.1 ± 13.3 vs. 79.6 ± 12.6 mmHg). Consistent findings were reported by Pierin et al. that the systolic and diastolic BP measurement (BP) in the upper arm with an appropriate cuff were significantly lower (n = 129,124 ± 21/73 ± 13 mmHg; P < 0.05) than forearm BPM (136 ± 19/82 ± 13 mmHg). Pierin et al. argued that although the forearm BP measurements overestimates the values of upper arm BP measurement, the forearm BPM could be corrected with an equation for systolic BPM = 33.2 ± 0.68 × systolic forearm BPM, and diastolic BPM = 25.2 ± 0.59x forearm diastolic BPM for obese patients with arm circumference between 32 and 44 cm. Tachovsky also supported the present study findings by reporting that the forearm BP had demonstrated a statistically significant higher systolic and DBP than the upper arm among 98 low-risk healthy female patients, aged 18–25 years (P < 0.05).
Clinically, the findings of the present study showed that the forearm had overestimated a mean systolic and diastolic pressure by approximately 2–10 mmHg in (72.31%) of the prenatal women. A cross-sectional study involving 510 same arm sequential paired BP measurements in 85 volunteers supported the present findings. The results revealed that the wrist NIBP consistently overestimated mean arterial, systolic, and diastolic pressure by approximately 10 mmHg, with the mean difference of the systolic pressure by 11.2 mmHg and the diastolic pressure difference by 10.2 mmHg. Emerick concluded that wrist NIBP may be a viable clinical alternative in situations where difficulty occurs with upper arm NIBP measurement.
Domiano et al. reported a consistent findings in their cross-sectional study among conveniently selected 106 low income, normotensive ambulatory population. Although the analyses revealed a higher SBP mean difference by 4.0 mmHg and DBP by 10.2 mmHg in the forearm than the upper arm BP readings. Domiano et al. postulated that higher forearm BP values could be compensated by subtracting 10 mmHg from the measured values or simply by elevating the wrist about 15 cm and taking the BP at face value.
Vinyoles et al. reported a similar finding in their cross-sectional descriptive study conducted in an ambulatory setting among 54 conveniently selected patients. The analyses revealed mean differences between arm and forearm measurements by 5.5 mmHg (95% CI: 14.5–25.5) for SBP and 1.53 mmHg (95% CI, −13.5–16.5) for DBP. Pierin et al. also reported that the systolic and diastolic BPM of an upper arm with an appropriate cuff were significantly lower (P < 0.05) than forearm BPM with a standard cuff. The researcher hypothesized that overestimated BP values by forearm could be corrected with an equation.
On the contrary, Palatini et al. who investigated the wrist versus upper arm BP measurements by conventional sphygmomanometer among 85 normotensive individuals discouraged the use of wrist BP measurements suitable alternative to traditional measurement at the upper arm due to consistent overestimated BP discrepancy of 8.2 ± 9.7/9.2 ± 6.4 mmHg in the forearm than the upper arm. Although the present study reported a marked difference between systolic and diastolic noninvasive measurements of BP in the upper arm and forearm, it showed a positive linear relationship between them in systolic (r = 0.849) and diastolic (r = 0.816) BP measurements at P < 0.05 by Pearson product-moment correlation coefficient. Schell et al. reported a similar findings demonstrating a strong correlation between the upper versus forearm SBP (0.88; P < 0.001) and DBP (0.76 P < 0.001) with the mean values ranging from 15 mmHg in mean arterial pressure to 18.4 mmHg in systolic pressure. Singer et al. reported similar correlations between forearm and upper arm systolic and DBPs by r = 0.75 (P < 0.001) and = 0.72 (P < 0.001). Schell et al. concluded that forearm BP is a fairly good predictor of standard upper arm and it can be used as substitute for standard BP in the upper arm.
The auscultatory mercury sphygmomanometer BP measurements have always been regarded as the gold standard for clinical measurements of BP. It is the bedrock of the diagnosis and treatment of hypertension and has been the standard method used in the major epidemiologic and treatment trials of the past 50 years. In this study, the BP readings were taken by calibrated mercury sphygmomanometer by the two trained midwives. Wong et al. reported a consistent finding of insignificant difference in the BP measurements by oscillometric BP devices and auscultatory mercury sphygmomanometer in children aged 5–15 years. Rogers et al. agreed with these results by observing no difference in BP measurements in either of the oscillometric device and auscultatory mercury sphygmomanometer between observers or left versus right arm among normotensive adults.
Implications for practice
This study adds important information to the literature supporting the need to detect difference in BP in the upper versus lower arm, among pregnant women. This simple, noninvasive test has the potential in identifying difference in BP to improve maternal and perinatal outcomes.
The study has the limited ability to generalize the findings to women with risk factors complicating pregnancy, and the findings should be interpreted within the context of its limitations that the BP readings were measured by mercury sphygmomanometer with standard adult and pediatric cuff.
| Conclusion|| |
The findings of the study revealed a statistically significant difference in BP measurements in systolic and DBP values between the upper and lower arm. The BP obtained at the forearm is higher than the BP measurements obtained at the upper arm location. Despite strict adherence to optimal cuff size and measurements of BP in the brachial and radial artery at heart level, with the calibrated mercury sphygmomanometer among seated normotensive prenatal women in stable condition is not identical. This must form a base for clinical decision-making, whenever the forearm is considered as a surrogate to the upper arm for BP measurements.
The author would grateful to all the participants, midwives, obstetricians, biostatistician, and medical officers of the study setting for their support and participation.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]