Correlation of patient characteristics with arm and finger measurements in Asian parturients: a preliminary study

BACKGROUND: Accurate blood pressure (BP) measurement depends on appropriate cuff size and shape in relation to the arm. Arm dimensions outside the recommended range of cuff sizes or trunco-conical arms may result in inaccurate BP measurements. Measuring BP using finger cuffs is a potential solution. Arm cuff size is based on mid-arm circumference (MAC), and trunco-conicity is quantified by conicity index. We aimed to determine the correlation of MAC, body mass index (BMI), and weight with conicity index. METHODS: A prospective cohort study was conducted in the KK Women’s and Children’s Hospital where third trimester parturients scheduled for cesarean delivery were recruited after obtaining informed consent. Parturients were asked to rate their experience with time taken to obtain BP readings, cuff popping off during measurement, need to move the cuff from the upper arm to lower arm or leg, and need to change to a different cuff. Our primary outcome was the correlation between MAC and conicity index, calculated using Pearson’s correlation. The correlation between BMI and weight with conicity index was also determined. RESULTS: We enrolled 300 parturients. Moderate correlation was found between left MAC and left conicity index (r = 0.41, 95% CI 0.32 to 0.51), and right MAC and right conicity index (r = 0.39, 95% CI 0.29 to 0.48). Weight (r = 0.35 to 0.39) and BMI (r = 0.41 to 0.43) correlated with conicity index in this study. MAC of 1 parturient fell outside the recommended range for arm cuffs, but all parturients fit into available finger cuffs. Obese parturients had increased problems with arm cuffs popping off and needing a change of cuff. CONCLUSIONS: BMI better correlated with conicity index compared to MAC or weight. Standard finger cuffs were suitable for all parturients studied and may be a suitable alternative. TRIAL REGISTRATION: Clinicaltrials.gov NCT04012151. Registered 9 Jul 2019