forearm BP measurements: are they accurate?

16 Oct



(scroll to the bottom for the 30-second recap)


study from Spain, 54 patients, 108 arms (n=108).  BMI >26 kg/m2

  • Mean differences between arm and forearm measurements
    • SBP: 5.5 mmHg (95% CI, -14.5 to 25.5) 
    • DBP: 1.53 mmHg [95% CI, -13.5 to 16.5] 
  • their conclusion: not that accurate
  • my 2 cents: could the difference is due to crappy upper arm measurements in obese folks?


SUNY study, 151 patients

  • mean forearm SBP 129.8+/-20.7 mm Hg
  • upper arm SBP 126.2+/-17.6 mm Hg (p = 0.002).
  • mean forearm DBP 80.7+/-14.5 mm Hg
  • upper arm DBPs 76.8+/-13.4 mm Hg (p<0.001).
  • differences between forearm and upper arm systolic and diastolic BPs were within 20 mm Hg in 86% and 94% of patients, respectively.
  • their conclusion: Forearm BP is a fairly good predictor of standard upper arm BP in most patients
  • my 2 cents: 20mmHg is a big difference, but if you can’t get an upper arm BP due to BMI/size, its better than nothing


study from Canada, 51 patients, 1285 forearm, & intra-arterial pressures; 352 later got upper arm BPs in post-op

  • compared upper arm & forearm pressure to OR intra-arterial pressures (seems most relevant)
    • Correlation between the intra-arterial and the forearm measures was 0.90 (P < 0.001)
    • Compared to intra-arterial, the forearm method overestimated systolic (6 ± 16 mm Hg, P < 0.001) and underestimated diastolic blood pressure (2 ± 11 mm Hg, P = 0.03).
    • Compared to intra-arterial, upper-arm underestimated systolic (8 ± 16 mm Hg, P < 0.01) and overestimated diastolic blood pressure (9 ± 7 mm Hg, P < 0.001).
  • their conclusion: magnitude of differences between the intra-arterial and forearm method was less than differences between the intra-arterial and upper-arm method.  
  • my two cents: sounds like forearm pressures are as crappy as upper arm BPs in large BMI folks, so somewhat useable, though forearm tends to overestimate the SBP



some variable differences in upper arm and forearm BPs in large BMI patients

most promising is that intra-arterial BPs matched up ok with forearm BPs compared to upper arm BPs (i.e. just as [in]accurate)

in a pinch, if you can’t use the upper arm (size/fistula), try the forearm — beats nothing

however, this may be a time where mentation/peripheral pulses/perfusion may be as useful a clinical indicator as the BP number

OR, if your patient’s sick, throw in an arterial line.


References: spain study; canadian study; SUNY study; picture


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s

%d bloggers like this: