Background: Accurate blood pressure (BP) measurement is essential in the emergency department (ED), where it serves as a key marker of hemodynamic stability and informs critical management decisions. Improper technique and incorrect cuff sizing can lead to falsely high or low readings, impacting patient care. The issue of BP cuff size has been studied in manual BP cuffs previously, but there is scant literature on automatic BP cuffs. Inaccurate BP readings in the ED can result in inappropriate interventions, including unnecessary medication administration or missed diagnoses. Given its clinical significance, understanding the impact of cuff size on BP measurements is crucial for optimizing patient outcomes in emergency settings.

Paper: Ishigami J et al. Effects of Cuff Size on the Accuracy of Blood Pressure Readings The Cuff(SZ) Randomized Crossover Trial. JAMA Intern Med. 2023;183(10):1061-1068. PMID: 37548984

Clinical Question: Does using a standard (regular) sized BP cuff on all patients significantly alter BP readings compared to using an appropriately sized BP cuff for the particular patient?

What They Did:

• Randomized crossover trial of community-dwelling adults
  • Participants were assigned to receive blood pressure measurements using different BP cuff sizes in a random order.
  • All participants were exposed to an appropriate-sized cuff, a cuff that was too small, and a cuff that was too large.
• Blood Pressure Measurement Protocol
  • The right arm was used for all measurements for standardization unless research staff felt there was a compelling reason to use the left arm.
  • The protocol was very standardized. Every patient walked for 2 minutes before BP measurement, rested for 5 minutes, and each BP was taken 30 seconds apart. Participants were seated with their backs, feet, and arms supported.

Population:

• 195 total participants were recruited via the following methods:
  • BP screening events at a public food market
  • BP screening events at a senior housing facility
  • Mailing study information to previous research participants
  • Placement of study brochures in hypertension clinics
  • Physician referrals of patients being treated for HTN

Inclusion Criteria: 

• Participants > 18 years old
• Normotensive or hypertensive individuals

Exclusion Criteria:

• Rashes, open sores, or wounds to upper extremities
• Gauze dressings or casts to the bilateral upper extremities
• Edema to the upper extremities
• Paralysis of the upper extremities
• AV Fistula present on both arms
• Lack of capacity to consent
• Pregnancy
• Arm circumference > 55 cm

Outcomes:

• Primary: Difference between the mean SBP and DBP with a standard regular sized BP cuff vs an appropriately sized BP cuff for the participant. Secondary:
• Difference in the mean SBP and DBP using a too-small or too-large cuff vs using an appropriately sized BP cuff for the participant.

Results: 

Primary Results:

• The mean age of participants was 54 years old with a SD of 16
• The mean BMI of the participants was 28.8 with a SD of 8.1
• Mean blood pressure readings:
  • Small BP cuff participants: 119.6/71.5
  • Regular BP cuff participants: 120.9/72.8
  • Large BP cuff participants: 122.7/75.7
  • Extra-large BP cuff participants: 124.5/79.3

Key Findings:

• When a cuff too large was used, the SBP and DBP readings were inaccurately low.
• When a cuff too small was used, the SBP and DBP readings were inaccurately high.
• When a cuff two sizes too small was used, the SBP and DBP readings were even more inaccurately high.

Secondary Outcome:

• BP difference using Too-Small or Too-Large BP cuffs across cuff sizes.
• The magnitude of difference in BP readings was greater when the cuff was either two sizes too big or two sizes too small for the participant as opposed to one size too big or one size too small.

Strengths:

• Randomized crossover design to control between subject variability
• Protocol in place to ensure all BP measurements were taken consistently and that cuff size for each participant was chosen consistently.
• Sample size of 196 participants. Large enough to provide sufficient statistical power.
• Relevance to clinical practice: BP measurement errors due to the usage of the incorrect cuff size are a concern in everyday clinical medicine.

Limitations:

• Limited detailed demographic and clinical data on participants limit external validity. Additionally, the study does not take the background health status of the participants into account. Specifically, a dedicated study in individuals with diagnoses of HTN or obesity would be valuable.
• Lack of long-term follow-up. In a clinical setting, BP measurements are often taken over multiple visits, and incorrect cuff size could affect longitudinal BP management.
• The study did not investigate whether the type of device (manual vs automated) influences the accuracy of BP measurements in relation to cuff size.
• The study did not investigate whether the anatomic location from which the blood pressure was taken (wrist vs forearm vs upper arm) influences the accuracy of the BP measurements in relation to cuff size.
• BP measurements were taken by trained research staff subscribing to a rigorous protocol. While this is a strength in terms of the trustworthiness of the data, inaccurate readings due to inappropriate cuff sizes are likely more prevalent in real-world clinic scenarios. Additionally, other confounding factors, including arm placement, activity before blood pressure readings, etc., is likely more common in real-world clinical scenarios.
• Finally, as Emergency Medicine physicians, the generalizability of this data to our patient population is limited, as this study did not include acutely ill patients.

Discussion:

• While all SBP and DBP differences were statistically significant when compared to measurements taken with an appropriately sized BP cuff, the clinical relevance of these differences varied depending on the cuff sizes being compared. For instance, when a small cuff was appropriate, but a regular cuff was used, the resulting BP measurement was only 3.6 mmHg lower—a difference unlikely to alter clinical decisions or interventions. However, when an extra-large cuff was needed but a regular cuff was used instead, the BP reading was elevated by 19.5 mmHg, a discrepancy that would be clinically significant in nearly all patient encounters. Thus, ultimately, while some differences were minor, the study as a whole presents a compelling argument for the importance of proper BP cuff size selection.
• In the emergency department, blood pressure measurements often dictate the clinical interventions that we choose. Therefore, emergency departments should prioritize ensuring that appropriate cuff sizes are available for patients of varying body types.
• Future research could build on the findings of this study. For our specialty, research done to evaluate the accuracy of BP readings in the emergency department or even on an inpatient unit would be most helpful. Outside of the acute care setting, other possible studies could explore the impact of cuff size on specific patient populations (HTN, obesity), evaluate the long-term effects of cuff-related measurement errors, or investigate how automated anatomic location of BP measurement (upper arm vs forearm vs wrist) impacts the accuracy of BP measurements related to cuff size.

Author Conclusions: “In this randomized crossover trial, miscuffing resulted in strikingly inaccurate BP measurements. This is particularly concerning for settings where 1 regular BP cuff size is routinely used in all individuals, regardless of arm size. A renewed emphasis on individualized BP cuff selection is warranted.”

Our Conclusions:

• While this study was done in an outpatient setting, there are important implications for the emergency department. In the ED, selecting an appropriately sized BP cuff is essential as inaccurate BP readings directly impact the interventions a patient receives. For example, conditions like hypertensive emergency, ischemic and hemorrhagic stroke, and undifferentiated shock rely on accurate blood pressure readings for diagnosis and intervention.

Clinical Take Home Point:

• An incorrectly sized blood pressure cuff can lead to dangerously inaccurate readings and poor clinical decisions. Every healthcare facility must stock multiple cuff sizes and ensure proper fit for each patient.

For More Thoughts on Similar Topics Check Out These Other Posts on REBEL EM:

• Asymptomatic Hypertension: A 2 Year Look Back from Canada
• Elevated Asymptomatic Hypertension: To Treat or Not to Treat?
• REBEL Core Cast 65.0 – Idiopathic Intracranial Hypertension
• Intensive Blood Pressure Control Doesn’t Benefit Patients with Acute Cerebral Hemorrhage (ATACH-2)

References: 

1. Ishigami, J., Charleston, J., Miller, E. R., Matsushita, K., Appel, L. J., & Brady, T. M. (2023). Effects of cuff size on the accuracy of blood pressure readings: the Cuff (SZ) randomized crossover trial. JAMA internal medicine, 183(10), 1061-1068. PMID: 37548984
2. Picone, D. S., Schultz, M. G., Otahal, P., Aakhus, S., Al-Jumaily, A. M., Black, J. A., … & Sharman, J. E. (2017). Accuracy of cuff-measured blood pressure: systematic reviews and meta-analyses. Journal of the American College of Cardiology, 70(5), 572-586. PMID: 28750701

Post Peer Reviewed By: Anand Swaminathan, MD (Twitter/X: @EMSwami)