Article Text

Download PDFPDF
Evaluation of the B-Smart manometer and the CompuFlo computerized injection pump technology for accurate needle-tip injection pressure measurement during peripheral nerve blockade
  1. Robyn S Weisman,
  2. Nirav P Bhavsar,
  3. Kathleen A Schuster and
  4. Ralf E Gebhard
  1. Department of Anesthesiology, University of Miami – Miller School of Medicine, Miami, Florida, USA
  1. Correspondence to Robyn S Weisman, Department of Anesthesiology, University of Miami-Miller School of Medicine, Miami, FL 33136, USA; rweisman1{at}


Background and Objectives The exact mechanism of peripheral nerve blocks causing/leading to nerve injury remains controversial. Evidence from animal experiments suggests that intrafascicular injection resulting in high injection pressure has the potential to rupture nerve fascicles and may consequently cause permanent nerve injury and neurological deficits. The B-Smart (BS) in-line manometer and the CompuFlo (CF) computerized injection pump technology are two modalities used for monitoring pressure during regional anesthesia. This study sought to explore the accuracy of these two technologies in measuring needle-tip pressures in a simulated environment.

Methods In seven simulated needle–syringe combinations, the BS and the CF devices were connected in series through a closed system and attached to a digital manometer at the tip of various needles. The pressures were evaluated in three trials per needle-syringe combination. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy (F1 Score) were determined for each needle type and overall.

Results For pressures ≥15 psi and ≥20 psi, respectively, the CF device demonstrated a sensitivity of 100%, 100%; specificity of 96%, 98%; positive predictive value 93%, 93%; and negative predictive value of 100%, 100%. The BS device demonstrated a sensitivity of 60%, 100%; specificity of 99%, 95%; positive predictive value of 96%, 85%; and negative predictive value of 85%, 100%. Accuracy, as measured by the F1 Score, for detecting a pressure of ≥15 psi was 0.96 for the CF and 0.74 for the BS.

Conclusions Future research is needed to explore in-vivo performance and evaluate whether either of these devices can impact on clinical outcomes.

Statistics from

Request Permissions

If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.


  • Funding This study was solely funded by departmental resources, University of Miami, Department of Anesthesiology.

  • Competing interests REG has received consulting fees as a member of the scientific advisory board for Milestone Scientific, the company that makes one of the products that is being studied in this manuscript. REG’s scientific role in this study was to contribute to writing the manuscript. The authors have volunteered to share raw data and videos for independent analysis on request. All additional authors declare no conflicts of interest.