Effects of Cuff Size on the Accuracy of Blood Pressure Readings The Cuff(SZ) Randomized Crossover Trial

 

Written By: Faria Rahman, MD; Edited by: Brian Smith, MD, MA, MMSc-Med

 

Does using a regular (standard) sized BP cuff for all patients significantly alter automatic BP readings as compared to using an appropriately sized BP cuff for each patient?

Accurate BP measurement is essential in the emergency department where it can help guide critical medical decisions. Improper BP readings due to incorrect cuff sizing can lead to falsely high or low readings. BP cuff size effects have previously been studied on manual BP cuffs, but there is little to no literature on its effects on automatic BP cuffs. This study looks at automatic BP cuff size and its effect on BP readings for patients.

How was the study conducted?

Study design

  • Type: Randomized crossover trial

  • Period: March 16- October 25, 2021

  • Location: Baltimore, Maryland

Who was studied?

195 total participants were recruited via:

  • BP screening events at public food market and senior housing facility

  • Targeted mailing to previous research participants

  • Study brochures in hypertension clinics

  • Physician referrals of patients being treated for hypertension

Inclusion criteria: >18 years old, normotensive or hypertensive individuals

Exclusion criteria: 

  • Rashes, open sores, or wounds to upper extremities

  • Edema to upper extremities

  • Dressings or casts to upper extremities

  • Paralysis of upper extremities

  • AV fistula present on both arms

  • Lack of capacity to consent

  • Arm circumference >55cm

  • Pregnant

What did they measure?

  • Primary: difference between mean SBP/DBP using regular sized BP cuff vs appropriately sized BP cuff for each participant

  • Secondary: difference in mean SBP/DBP using too-small or too-large cuff vs appropriately sized cuff for each participant

What were the outcome results?

  • Primary: 

    • When a cuff size too large was used, the SBP and DBP readings were inaccurately low

    • When a cuff size too small was used, the SBP and DBP readings were inaccurately high

  • Secondary: 

    • When a cuff size was more than one size too big or small, the difference in BP readings were greater in magnitude 


Study Strengths

  • Randomized crossover design

  • Strict protocol for measuring BP to ensure consistency in BP readings

  • Large sample size of 195 participants


Study Limitations

  • Study does not take background health status of participants into account (i.e. BMI, comorbidities)

  • Does not investigate whether anatomic location of where the BP was taken affects the accuracy of the BP reading

  • Although the authors used triplicate readings for BP, there could still be measurement variability that could affect estimates for individuals

  • Some BP size subgroups had small numbers, limiting the power of the study

Bottom line

Using an appropriate sized cuff to measure BP in a patient is important, especially in the emergency department. Using a cuff that is too large or too small can result in inaccurate BP readings which can be detrimental to patient care. 

 
Booth EM