BP Measurement at the Wrist?

Accurate BP measurement requires multiple steps, including appropriate cuff sizing; however, accurate measurement is well known to be less reliable in patients who have obesity, owing to a range of factors including circumference, length, and shape of the arm itself: 

  • Patients with a large upper arm circumference may also have short upper arm length. In these patients, an appropriately sized BP cuff in terms of circumference may be disproportionately long (i.e., the elbow end of the cuff may extend past the elbow by several centimeters), leading to inaccurate BP measurement;
  • BP cuffs are cylindrical in shape, but the upper arm typically has a conical shape (i.e., wider at the shoulder than at the elbow). The conical shape is often more pronounced in patients with obesity, which may also contribute to inaccurate BP measurement.

There is limited data on alternative sites for BP measurement, including the wrist, forearm, and leg. Of these, there is some evidence that measurement at the wrist may be a reasonable alternative in adult patients for whom upper arm measurement (the gold standard) is problematic. Consider the following statements from the American Heart Association and the Canadian Hypertension Guidelines: 

  • Measurement of Blood Pressure in Humans: A Scientific Statement from the AHA (2019): “If an extra-large cuff does not fit, BP may be measured on the wrist. A meta-analysis of adults who were obese reported a sensitivity of 97% and specificity of 85% for identifying hypertension when BP measured in the upper arm was compared with the gold standard of intra-arterial measurements. With upper-arm BP as the gold standard, wrist measurements had better test characteristics (i.e., sensitivity and specificity) for diagnosing hypertension compared with BP measurements taken on the forearm or finger.”
  • Canadian Hypertension Guidelines (2018): “Because of the limitations of the available studies to date, an appropriately sized upper arm cuff remains the standard for BP measurement. However, when upper arm measurements are not possible because of extreme size of the arm or pain, a wrist measurement (with the arm and wrist held at the level of the heart) may be used. When possible, concordance of wrist and upper arm device measurements should be demonstrated before the use of wrist BP measurements.”

Nevertheless, the overall evidence is mixed. Radial BP is known to be higher than brachial BP. A 2016 study found that wrist cuffs had poor reliability when used at home, largely a result of patients using them incorrectly, and may suggest the need for initial instruction on appropriate use. And the majority of wrist cuffs on the market have not been studied. In fact, there are only 5 validated wrist BP monitors on the US market. 

Given the potential issues with obtaining accurate BP measurements in patients with obesity, do you think the above evidence supports the use of a wrist cuff in a primary care clinic?

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