Measuring blood pressure using the mercury sphygmomanometer

The impact of sphygmomanometer placement and cuff placement on blood pressure measurements

Background

Hypertension is the most significant global risk factor for mortality and morbidity, making standardized blood pressure measurement crucial.

Objectives

To investigate whether the location of blood pressure monitors and the positioning of cuffs yield differing results in blood pressure measurements.

Methods

Patients admitted to the Affiliated Hospital of Jiujiang College between 1 January 2022 and 30 June 2023 were enrolled in this study and randomly allocated into four groups. These groups were defined based on the positioning of monitoring equipment as follows: varied placements of cuffs on automatic blood pressure monitors, different heights for mercury column blood pressure monitors, varied heights for automatic blood pressure monitors, and different orientations for the cuff airbag tubes on electrocardiogram monitors. Blood pressure was measured and recorded for each group, followed by an analysis of the variations in readings across the different setups.

Results

In the first cohort of 763 individuals, mean systolic blood pressure measured at the standard upper arm site was 128.8 ± 10.5 mmHg, compared to 125.3 ± 10.4 mmHg at the elbow fossa. The corresponding diastolic pressures were 79.2 ± 10.7 and 75.0 ± 10.6 mmHg, respectively. The difference in systolic pressure between these positions was significant at 3.48 ± 3.22 mmHg (t₁ = 29.91, p₁ < 0.001) and for diastolic pressure at 4.23 ± 1.31 mmHg (t₂ = 88.98, p₂ < 0.001). For the subsequent groups, involving 253, 312, and 225 individuals, respectively, blood pressure measurements were analyzed and compared across different methods within each group. All p-values exceeded 0.05, indicating no statistically significant differences.

Conclusions

Blood pressure values measured at the elbow fossa position using an upper arm-type automatic sphygmomanometer were found to be lower than those measured at the upper arm position, with a difference of 3.48 mmHg for systolic and 4.23 mmHg for diastolic pressures. It is therefore essential to position the cuff correctly, specifically 2-3 cm above the elbow fossa, when utilizing an upper arm-type automatic sphygmomanometer for blood pressure monitoring. Conversely, the placement of the mercury column sphygmomanometer and the automated sphygmomanometer at varying heights had no significant effect on blood pressure readings. Similarly, the orientation of the electrocardiogram's cuffed balloon tube, whether facing upward or downward, did not influence blood pressure measurement outcomes.

Accuracy of non-invasive blood pressure measurements in obese patients

This article describes an evidence-based literature review, comparing upper arm and forearm blood pressure measurements using non-invasive devices on obese patients. The focus on blood pressure monitoring was in response to regularly witnessing inappropriately applied blood pressure cuffs on obese patient's upper arms in practice. An inaccurately obtained blood pressure measurement can result in the misdiagnosis and treatment of hypertension. As the prevalence of obesity grows worldwide, healthcare settings need to ensure they have the necessary equipment and trained staff to accurately measure obese patients' blood pressure. The aim of this review was to identify whether a forearm measurement provided a suitable alternative to upper arm measurements. The article discusses the development and execution of a search strategy, as well as the critical appraisal of a selected article. The results of the review demonstrated that forearm blood pressure measurements in obese patients do not replace upper arm blood pressure measurements taken with an appropriate cuff. It is recommended that further research is undertaken in order to identify suitable alternatives for obtaining an accurate non-invasive blood pressure measurement in obese patients.

Investigation of end-digit preference in blood pressure records of hospitalized chinese patients and analysis of risk factors

OBJECTIVE

End-digit preference is common in blood pressure (BP) measurement, but there are no data available on end-digit preference in China. The purpose of this study was to investigate the frequency of end-digit preference in Chinese hospitalized patients and to explore its risk factors.

METHODS

We used systematic sampling to investigate the BP values and related characteristics in records from Chinese patients hospitalized at a university-affiliated hospital in Shanghai, China. Data were collected from January to December 2010. Logistic regression models were created to analyze the relationship between potential risk factors and zero end digit in recorded BP values.

RESULTS

Of all 4511 patient records, 57.1% of patients were male. The mean age was 55.1 years (standard deviation [SD], 15.4 years). When admitted, the mean BP values were 124.6 mm Hg (SD, 14.3 mm Hg) for systolic blood pressure (SBP) and 77.5 mm Hg (SD, 8.6 mm Hg) for diastolic blood pressure (DBP). 81.8% and 81.2% of SBP and DBP values had an end digit of zero. 7.7% and 9.6% of SBP and DBP values had an end digit of "5." In the logistic regression analyses, female sex (odds ratio [OR], 1.34 for SBP, 1.24 for DBP), admission to a surgical department (OR, 2.04 for SBP, 1.88 for DBP), admission heart rate of ≥ 80 bpm (OR, 1.41 for SBP, 1.61 for DBP), and not having a history of hypertension (OR, 1.41 for SBP, 1.33 for DBP) were related to a high risk of having SBP and DBP values with a zero end digit. Patients with SBP values of ≥ 140 mm Hg had a high risk of having a zero end digit in SBP values (OR, 1.33) and a low risk of having a zero end digit in DBP values (OR, 0.67). Patients whose DBP values were ≥ 90 mm Hg had a high risk of having a zero end digit in DBP values (OR, 2.49).

CONCLUSION

The zero end-digit preference in recorded BP values of hospitalized patients in China was strong. Patients' sex, admission to a surgical department, admission heart rate, history of hypertension, and SBP and DBP values were risk factors that influenced the preference for zero as the end-digit BP value.

The inaccuracy of automatic devices taking postural measurements in the emergency department

Automatic devices are used to take postural blood pressures in the emergency department despite research proving their inaccuracy in taking single blood pressures. This study assessed the accuracy of an automatic device compared with a manual aneroid reference standard for determining orthostatic hypotension and postural drops at triage. Supine and standing blood pressures were taken with an automatic and a manual device in a sequential and random order, and postural drops were calculated. The manual device indicated 10/150 emergency department patients had orthostatic hypotension (7%) and the automatic device detected this with a sensitivity of 30% and a specificity of 91%. The automatic-manual differences were clinically significant in 13% of systolic drops and 37% of diastolic drops. Findings suggest that automatic devices cannot reliably detect or rule out orthostatic hypotension, indicating that triage nurses need to use manual devices to take accurate postural blood pressures for optimal patient care.

Using a reflective framework to assess skills - taking a manual BP

This article explores the skill of taking a manual blood pressure (BP) using a stethoscope and sphygmomanometer. Achieving competence in this area has become more difficult since the introduction of electronic BP monitors and less opportunity to practice manually. A reflective framework was used to guide the authors thoughts and actions related to this skill, as they learned how to competently undertake it. A particular learning style, which the authors identified as helpful is also discussed.

Providing best practice in manual blood pressure measurement

This article discusses the practical skills and underpinning knowledge needed when manually taking a patients blood pressure. The author defines blood pressure and the terms systolic and diastolic and explores the purpose of manual measurement. The article also goes on to examine what is meant by normal blood pressure, hypertension and hypotension, as well as factors that may influence blood pressure measurement. There is a brief outline of the equipment used for manually measuring blood pressure, followed by some factors that may affect the accuracy of the final reading. The author also highlights the different positions used for taking blood pressure and the arguments surrounding their respective merits. Finally, the article includes a practical step-by-step guide to manual blood pressure measurement.

Measuring blood pressure using an automated sphygmomanometer

There has been increasing pressure to remove medical devices containing mercury from clinical areas, which is leading to the demise of the mercury sphygmomanometer. As a result, automated blood pressure devices have been embraced by clinicians for their convenience and ease of use. However, it is essential that clinicians are aware of their limitations and are able to select the correct sphygmomanometer dependent upon the clinical need. It is a recommendation of the Independent Advisory Group that auscultation, as a method of determining blood pressure, should continue to be taught to healthcare professionals. Nevertheless, the reality is that in most clinical areas the automated sphygmomanometer is readily available and appears to be the device of choice. Therefore, where treatment protocols are based on accurate blood pressure readings, the clinician must ensure that the equipment used is appropriate for that application.

Nursing observations: knowledge to help prevent critical illness

Early warning scoring systems have made some progress in facilitating the earlier identification of critical illness. Nurses should, however, take a professional responsibility to ensure that they can understand the significance of the patient observations that they have recorded. The authors have illustrated, through the use of a case study, how an understanding of the physiological processes that influence trends in the patient's observations could be vital in the prevention of a serious life-threatening event. Conclusions drawn from analyzing these observations with a problem-solving approach can be effectively communicated to the multidisciplinary team and lead to more appropriate care delivery.

A comparison of two methods of blood pressure measurement

In current practice, a two-stage approach to measuring blood pressure (BP) has been widely accepted as the most accurate and reliable method. However, by changing the local haemodynamics, this procedure might alter the blood pressure. In a study of 39 subjects, blood pressure was measured using two indirect methods (two-stage and one-stage approaches). Results showed no statistically significant difference in values for systolic blood pressure obtained from the two methods. Statistically significant lower diastolic blood pressure values were obtained using the two-stage compared to the one-stage approach. It is proposed that initial inflation of the cuff to estimate systolic blood pressure in the two-stage approach might lead to reactive hyperaemia and, therefore, a lower diastolic value. This two-stage approach might not provide the accurate readings it claims, and in addition it requires more time and subjects the patient to longer periods of stress.