NONINVASIVE PREDICTION OF INTRACRANIAL-PRESSURE CURVES USING TRANSCRANIAL DOPPLER ULTRASONOGRAPHY AND BLOOD-PRESSURE CURVES

Background and Purpose Until now the assessment of intracranial pressu re (ICP) required invasive methods. The objective of this study was to introduce an approach to a noninvasive assessment of continuous ICP c urves. Methods The intracranial compartment was considered a ''black b ox'' system with an input signal, the arterial blood pressure (ABP), a nd an output signal, the ICP. A so-called weight function described th e relationship between ABP and ICP curves. Certain parameters, called transcranial Doppler (TCD) characteristics, were calculated from the c erebral blood flow velocity (FV) and the ABP curves and were used to e stimate this weight function. From simultaneously sampled FV, ABP, and (invasively measured) ICP curves of a defined group of patients with severe head injuries, the TCD characteristics and the weight function were computed. Multiple regression analysis revealed a mathematical fo rmula for calculating the weight function from TCD characteristics. Th is formula was used to generate the ICP simulation. FV, ABP, and ICP r ecordings from 11 patients (mean age, 46 +/- 14 years) with severe hea d injury were studied. In each patient, ICP was computed by a simulati on procedure, generated from the data of the remaining 10 patients. Th e simulation period was 100 seconds. Results Corresponding pressure tr ends with a mean absolute difference of 4.0 +/- 1.8 mm Hg between comp uted and measured ICP were observed. Shapes of pulse and respiratory I CP modulations were clearly predicted. Conclusions These results demon strate that this method constitutes a promising step toward a noninvas ive ICP prediction that may be clinically applicable under well-define d conditions.