Discrepancy between internal and external intracranial pressure transducers:

Quantification of an old source of error in EVDs? Sometimes the numbers don’t add up

David Darrow, MD, MPH, Alex Lee-Norris, MS, Anthony Larson, BS,
Uzma Samadani, MD, PhD, Theoden I. Netoff, PhD

Could measurement discrepancies lead to different treatments? Besides being the leading cause of death and disability, traumatic brain injury (TBI) is also associated with significant neurological consequences and increased intracranial pressure. ICP monitoring remains a crucial element in treatment protocol to determine the risk for stroke and possible herniation.

Experts examined TBI patient data from 500 hours of continuous recordings and compared 73 hours of simultaneous measurements from internal and external transducers.  Significant discrepancies were reported in measurements from the intracranial transducer (Integra Flex Ventricular catheter) and an external transducer.  The mean difference was found to be 5 mmHg with the externally measured pressure reading higher than the internal reading in all studied patients.

From a cohort of six patients with severe TBI, the external transducer, requiring frequent adjustments and changes in the zero height, was the cause of changes in pressure readings suggesting that in this study the internal transducer (Integra FVC, a.k.a.VTUN) was more accurate. The internal transducer (VTUN), after initial zeroing, did not show any significant drift and provided more accurate pressure readings than intermittent externally transduced ICP readings which due to zero height changes over the course of days/week could mislead clinical judgement.

In this article, Dr. Darrow et al examine the discrepancies in ICP readings between internal measurements using the Integra Flex Ventricular Catheter (FVC a.k.a. VTUN) and an externally transduced catheter system.

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10.1016/j.wneu.2019.07.213

September 1, 2020
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