Noninvasive Assessment of ICP: Evaluation of New TBI Data

Background : In a previously introduced mathematical model, intracranial pressure (ICP) was noninvasively assessed using cerebral blood flow velocity (CBFV) and arterial blood pressure (ABP). In this study this method is evaluated using new data from patients with traumatic brain injury (TBI). Materials and Methods: Three hundred fifteen data recordings of 137 patients (114 men; age 14-78 years, mean age 37 +/- 17 years) with severe TBI were studied. CBFV, ABP, and invasively assessed ICP were simultaneously recorded for 1 h. Noninvasive ICP (nICP) was calculated and compared with ICP. Results: On 315 recordings, average deviation between ICP and nICP (+/- standard deviation) was 4.9 +/- 3.3 mmHg. The standard deviation of differences (ICP - nICP) was 5.6 mmHg. The 95 % confidence interval of ICP prediction ranged from -9.6 to 12.3 mmHg. Mean ICP was 16.7 mmHg and mean nICP was 18.0 mmHg. When nICP was adjusted by their difference 1.3 mmHg (nICPadj=nICP-1.3), the 95 % confidence limits of ICP prediction became +/- 11.0 mmHg. In recordings with highly dynamic ICP signals (n = 27), ICP and nICP correlated on average with R = 0.51 +/- 0.47. Conclusions : nICP assessment showed reasonable accuracy and may be used in clinical studies of patients without any indication for ICP probe implantation.