1. Non-invasive assessment of intracranial pressure - a plugin function of ICM+ system
B. Schmidt, M. Czosnyka*, P. Smielewski*, R. Plontke,
J. Schwarze, J. Klingelhöfer
Dept. of Neurology, Medical Centre Chemnitz, Germany
* Ac. Neurosurgical Unit, Addenbrooke’s Hospital, Cambridge, UK

2. Non-invasive ICP assessment procedure - for scientific use only -
 The procedure calculates Intracranial Pressure from
Arterial Blood Pressure and Transcranial Doppler
Blood Flow Velocitiy of Middle Cerebral Artery
 Patented: by Patent Nr. DE
 Distributed by the authors as a Plugin of
ICM+ Monitoring Software / University Cambridge, UK
- for scientific use only -

3. The list of functions in ICM+ can be extended by plugins
The list of functions in ICM+ can be extended by plugins. One such plugin already available for ICM+ enables non-invasive calculation of ICP from TCD FV and ABP signals in real time.
ICP
Non-invasive ICP
ICP
Non-invasive ICP

4. How to insert nICP plugin into ICM+:.
- The non-invasive ICP plugin is a DLL file, developed in a C++ Borland environment.
- Copy the plugin into the ICM+ plugin folder,
e.g. pathname is "C:\Documents and Settings\All Users\Documents\ICM+\Plugins\"
- Now start ICM+. The plugin should be shown in the registration dialogue under "3rd Party Plugins”.
You send us the registration data of your ICM+ license, which contains name,
company and ICM+ install code.
The data should be exactly the same as it is in
the ICM+ registration form.
- Using this data we calculate your registration key
for the nICP plugin and send it back to you by .
- You enter the registration key of this plugin in the
ICM+ dialogue. This activates the nICP plugin,
unlimited in time. DE

5. Basic principle of the procedure
Calculate the signal of intracranial pressure (ICP)
from signals of
arterial blood pressure (ABP) and blood flow velocity (FV) of the middle cerebral artery (MCA)

6. Non-invasive ICP assessment – basic method
TCD-characteristics
{ tcdj } j = 0, ..., m FV
ABP
weight function
ABP ® ICP
{ wi } i = 0, ..., n
nICP
(non-invasive ICP)
FV : blood flow velocity in middle cerebral artery
ABP: arterial blood pressure
ICP: intracranial pressure
TCD: transkranial Doppler ultrasound
weight function = impulse response:
signal transformation,
time domain equivalent of transfer function

7. S Generation of the nICP Procedure FV ABP ICP w  A * tcd + B
Signal data of reference patients FV
ABP
ICP
ICPj = ABPj-k * wk
k=0 S n
TCD characteristics
tcd = (tcd0, tcd1, ..., tcdm)
weight function
ABP ® ICP
w = (w0, w1, ..., wn)
Multiple Regression
analyses
w  A * tcd + B
A (n+1) x (m+1) Matrix
B n+1-dim. Vektor
(A,B) : nICP Matrix,
(n+1) x (m+2) Dim

8. non-invasive ICP assessment – basic method
weight function
ABP ® FV
{ tj } j = 0, ..., 12 FV
ABP
{ wi } = A * ( {tj}x , PI, dFV, ) + B
weight function
ABP ® ICP
{ wi } i = 0, ..., n
nICP
Matrix A, Vector B generated by multiple regression analyses of reference data
TCD-characteristics ® weight function ABP ® ICP
PI: Pulsatility index
dFV: diastolic FV

9. Results 1 - non-invasive ICP assessment
on average of
 patient-day recordings: mean DICP = 5.2 ± 3.7 mm Hg
95% CI = 12.4 mm Hg
median DICP = 4.2 mm Hg
 patient recordings: mean DICP = 5.0 ± 3.3 mm Hg
95% CI = 10.8 mm Hg
DICP = mean abs (ICP-nICP)

10. Bland-Altman Plot of nICP - ICP comparison
-30
-25
-20
-15
-10 -5 5 10 15 20 25 30 40 50
95% CI
Bland-Altman Plot of nICP - ICP comparison
on average of
Daily Recordings:
N = 315
nICP-ICP
[mm Hg]
(nICP+ICP)/2 [mm Hg]
-20
-15
-10 -5 5 10 15 20 25 30 40
Bland-Altman Plot of nICP - ICP comparison
on average of
Patient Recordings:
N = 137
nICP-ICP
[mm Hg]
95% CI
(nICP+ICP)/2 [mm Hg]

11. nICP - ICP comparison in recordings nICP - ICP comparison in patients40
ICP
[mm Hg]
y = 0,863x + 1 35 30 25 20 15 10 5 5 10 15 20 25 30 35 40 45
nICP - ICP comparison in patients 40
ICP
[mm Hg] 35 30 25 20 15 10 5 5 10 15 20 25 30 35 40
nICP [mm Hg]

12. Results 3 - non-invasive ICP assessment
nICP assessment replicates ICP trends
in recordings with high ICP dynamic:
 95th perc ICP > 5th perc ICP + 10 mm Hg , 33 recordings,
mean nICP - ICP correlation R = 0.53 ± 0.47
 90th perc ICP > 10th perc ICP + 9 mm Hg , 27 recordings,
mean nICP - ICP correlation R = 0.57 ± 0.46

13. Example 1
033040AL.1L5

14. Example 2
038080JM.0L5

15. Example 2
038080JM.0L5

16. Example 4
053022AW.0L5

17. Conclusions
 in the clinically relevant range of ICP the nICP assessment
showed a reasonable accuracy
 nICP assessment replicates ICP changes and trends
 nICP plugin of ICM+ may be used for clinical studies *
in patients without implanted ICP probes *
Pfister D, Schmidt B, Smielewski P, Siegemund M, Strebel SP, Rüegg S, Marsch SCU, Pargger H, Steiner LA. Intracranial Pressure in Patients with Sepsis. Acta Neurochir Suppl. 102:71-75, 2008
Schmidt B, Weinhold M, Czosnyka M, May SA, Steinmeier R, Klingelhöfer J. Accuracy of non-invasive ICP assessment can be increased by an initial individual calibration. Acta Neurochir Suppl. 102: 49-52, 2008
Schmidt B, Klingelhöfer J, Perkes I, Czosnyka M. Cerebral Autoregulatory Response Depends on the Direction of Change in Perfusion Pressure. J Neurotrauma. 26:1-6, 2009
Reinhard M, Neunhoeffer F, Gerds TA, Niesen WD, Buttler KJ, Timmer J, Schmidt B, Czosnyka M, Weiller C, Hetzel A (2010). Secondary decline of cerebral autoregulation is associated with worse outcome after intracerebral hemorrhage. Intensive Care Med 36(2):264-71, 2010
Oeinck M, Neunhoeffer F, Buttler K-J, Meckel S, Schmidt B, Czosnyka M, Weiller C and Reinhard M. Dynamic Cerebral Autoregulation in Acute Intracerebral Hemorrhage. Stroke. published online August 13, 2013;

18. Pfister D, Schmidt B, Smielewski P, Siegemund M, Strebel SP, Rüegg S, Marsch SCU, Pargger H, Steiner LA (2008). Intracranial Pressure in Patients with Sepsis. Acta Neurochir Suppl. 102:71-75
Schmidt B, Weinhold M, Czosnyka M, May SA, Steinmeier R, Klingelhöfer J (2008). Accuracy of non-invasive ICP assessment can be increased by an initial individual calibration. Acta Neurochir Suppl. 102: 49-52
Schmidt B, Klingelhöfer J, Perkes I, Czosnyka M (2009). Cerebral Autoregulatory Response Depends on the Direction of Change in Perfusion Pressure. J Neurotrauma. 26:1-6
Reinhard M, Neunhoeffer F, Gerds TA, Niesen WD, Buttler KJ, Timmer J, Schmidt B, Czosnyka M, Weiller C, Hetzel A (2010). Secondary decline of cerebral autoregulation is associated with worse outcome after intracerebral hemorrhage. Intensive Care Med 36(2):264-71
Maximilian Oeinck, Florian Neunhoeffer, Klaus-Juergen Buttler, Stephan Meckel, Bernhard Schmidt, Marek Czosnyka, Cornelius Weiller and Matthias Reinhard. Dynamic Cerebral Autoregulation in Acute Intracerebral Hemorrhage. Stroke. published online August 13, 2013;

19. S Flow diagram of the nICP procedure FV ABP nICP w  A * tcd + B
Signal data of current patient FV
ABP
nICP
every
10 Seconds
ICPj = ABPj-k * wk
k=0 S n
weight function
ABP ® ICP
w = (w0, w1, ..., wn)
TCD characteristics
tcd = (tcd0, tcd1, ..., tcdm)
w  A * tcd + B
A (n+1) x (m+1) Matrix
B n+1-dim. Vektor
(A,B) : nICP Matrix,
(n+1) x (m+2) Dim