Arm and Finger Measurement for Blood Pressure Surveillance

Study Overview
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Brief Summary
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Accurate blood pressure (BP) measurement is critical in peripartum care. The cuff and bladder sizes affects the accuracy of BP measurement. Current international BP measurement recommendations are based on mid-arm circumference (MAC). However, evidence have shown the discrepancies between these sizes, leading to inaccuracy of BP measurement. This study will measure arm and finger size of 300 parturients in third trimester to determine whether the MAC, finger measurement or body mass index (BMI) is the best clinical predictor for non-standard cuff sizes for BP measurement.

Detailed Description
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Accurate blood pressure (BP) measurement plays an important role in peripartum care as it is essential in detecting hypertensive disorders in pregnancy and medical decision making during the pregnancy. The cuff and bladder size have been highlighted as an important factor affecting the accuracy of BP measurement. Current international BP measurement recommendations are based on mid-arm circumference (MAC) assuming the arm is cylindrical in shape. However, evidence have shown a mismatch between these sizes, leading to BP overestimation or underestimation in obese patients. This is because the shape of the arm is a truncated cone instead of a cylinder, and the cuff will expand irregularly during inflation thus yielding inaccurate BP measurements. This is especially evident in Asian pregnant patients whereby no available guideline can recommend a suitable cuff for parturients with different MAC. Nexfin is a finger cuff device that can be a suitable alternative BP measurement device for such patients. In this study 300 parturients will be recruited in third trimester and undergoing nonemergent caesarean section in KKH. Patients' arm and finger sizes will be measured, and their user experience on current practices on BP measurement. The arm measurements will help to identify the proportion of women that may require non-standard cuff sizes for BP measurement. A conicity index will be determined whether the MAC, finger measurement or BMI is the best clinical predictor. The finger measurements will also help to determine the proportion of women that may require non-standard cuff sizes on the Nexfin device for BP measurement. The knowledge gathered in this pilot study will be used to design future studies in which the accuracy of Nexfin will be compared with standard BP measurement, which in turn will improve BP detection, subsequent patient monitoring and satisfaction.

Official Title
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Arm and Finger Measurement for Blood Pressure Surveillance

Conditions
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Hypertension, Pregnancy-Induced

Intervention / Treatment
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* Other: Physical measurement
* Other: Cuff size fitting


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: American Society of Anaesthesiologists physical status 1 or 2 (ASA 1 or 2) parturients at 32 or more weeks of gestation Multiparous or nulliparous; Age 21-50 years old; Undergoing Caesarean section in our institution. Exclusion Criteria: Emergent Caesarean section such that consent and measurements cannot be taken.

Ages Eligible for Study
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Minimum Age: 21 Years
Maximum Age: 50 Years

Sexes Eligible for Study
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Female

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Pregnant cohort<br>Parturients of gestational age >= 32 weeks will have measurements of arm length, MAC, proximal arm circumference, distal arm circumference, finger circumference to generate the conicity index. | Other: Physical measurement<br>* Parturients of gestational week >= 32 weeks will have their arms and fingers measured to generate the conicity index.<br>* Other names: Measurement of fingers and arms;Other: Cuff size fitting<br>* Fit on arm cuff and finger cuff as selected by investigators based on the measurement.<br>* Other names: Cuff fitting for arm and finger;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Arm length (Left, Right) | The distance (cm) between the tip of the acromion process to the tip of the olecranon process on the posterior aspect of the arm, with the elbow in the flexed position. | During antenatal visit (1-2 hours). One visit only | 
| Mid Arm circumference (MAC)(Left, Right) | The circumference (cm) of the arm at the mid-point of the arm length as measured above, with the arm hanging by the side. | During antenatal visit (1-2 hours). One visit only | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Proximal arm circumference (Left, Right) | Arm circumference (cm) of the arm measured at the axilla, with the arm hanging by the side. | During antenatal visit (1-2 hours). One visit only | 
| Distal arm circumference (Left, Right) | The circumference (cm) at the elbow above the elbow crease, with the arm hanging by the side. | During antenatal visit (1-2 hours). One visit only | 
| Finger circumference (Left, Right) | The circumference (cm) of the mid-point of the middle phalanx of the middle finger will be measured with the hands placed flat on a table. | During antenatal visit (1-2 hours). One visit only | 
| Feedback on experiences of previous BP measurement | Participants will also respond to a three-point rating scale (Never, sometimes, always) about their experience of the procedures for previous BP measurement during the current pregnancy, with questions such as the length of time taken to obtain a reading, the need to change a cuff when taking BP, the need to take BP on the leg and whether the arm felt uncomfortable when taking blood pressure. | During antenatal visit (1-2 hours). One visit only | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Blood pressure measurement, Conicity index, Mid arm circumference, Cuff size