Arm and Finger Measurement for Blood Pressure Surveillance

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.

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.