The purpose of this study was to examine the accuracy and reproducibility of intracranial pressure (ICP) measured by the external ventricular drainage (EVD) system. The effect of specific gravity (SpGr) of cerebral spinal fluid (CSF) on the accuracy of the EVD-measured-ICP was also determined. Sixty-two subjects with EVD system were included. The ventriculostomy catheter connected to both the ICP monitor and EVD system was used to measure ICP. ICP was repeatedly measured 6 times in three positions: head at 0 degree, head up 15 degree, and head up 30 degree. The accuracy of the EVD-measured-ICP was determined using the Pearson’s correlation, paired t-test, and the Bland-Altman method. Analysis of the reproducibility of ICP measurements by EVD system was done with the Pearson' correlation and coefficient of variation (CV). The mean ICP between two measurements was significantly correlated (r = .93, p ＜ .001) at head 0 degree position; the bias (mean difference) showed significant differences (p ＜ .001); the standard deviation was 2.0 ± 1.6 mmHg; and the limit of agreement (bias ± 2SD) were between − 1.2 and 5.2 mmHg. Position at head up 15 degree displayed significant correlation (r = .94, p ＜ .001); the bias showed significant differences (p ＜ .001); and the standard deviation was 2.1 ± 1.5 mmHg, with the limits of agreement being − 0.9 and 5.2 mmHg. At head up 30 degree, the correlation between measurements was significant (r = .95, p ＜ .001); the bias had significant difference (p ＜ .001); the standard deviation was 2.0 ± 1.6 mmHg; and the limits of agreement were − 1.2 and 4.9 mmHg. There was no significant correlation between SpGr of CSF and difference of mean ICP by EVD system and monitor measurements (p ＞ .05). The EVD-measured ICP had good reproducibility (p ＜ .001). The CV at head 0 degree was 3.69%, head up 15 degree was 6.62%, and head up 30 degree was 7.88%. In conclusion, the agreement of ICP measurements between the EVD system and monitor was poor and the SpGr of CSF did not affect this result. The results suggested good measurement at the supine position when ICP was measured by the EVD system.
- external ventricular drainage system
- intracranial pressure measurement