B. Schmidt et al., NONINVASIVE PREDICTION OF INTRACRANIAL-PRESSURE CURVES USING TRANSCRANIAL DOPPLER ULTRASONOGRAPHY AND BLOOD-PRESSURE CURVES, Stroke, 28(12), 1997, pp. 2465-2472
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.