Cerebral Tissue Oxygenation Can Be Used Instead of Cerebral Intravascular Oxygenation to Study Cerebral Autoregulation in

Prematurely Born Infants

Ir. D. De Smet*, Lic. J. Vanderhaegen**, Prof. Dr. G. Naulaers**

and Prof. Dr. Ir. S. Van Huffel*

KATHOLIEKE UNIVERSITEIT LEUVEN, BELGIUM

*DEPARTMENT OF ELECTRICAL ENGINEERING (ESAT-SCD)

**NEONATAL INTENSIVE CARE UNIT, UNIVERSITY HOSPITALS LEUVEN

Introduction

Problem : impaired cerebral autoregulationSolution : detect ΔHbD concordant with ΔMABP (with ΔSaO2=0)1

But …Problem : HbD (=HbO2-HbR) is not an

absolute valueSolution : prove that TOI may replace HbD

for measurement of impaired cerebral autoregulation

Acronyms :• MABP : mean arterial blood pressure• HbD : cerebral intravasc. oxygenation.• SaO2 : arterial oxygen saturation• TOI : cerebral tissue oxygenation_____________________________________________________[1] Tsuji et al., Pediatrics, 2000.

1. Introduction

2. Datasets

3. Methods

1. DC meth.

2. CPRT

3. Similarity meas.

4. Exp. results

5. Conclusion

Fig. : signals of interest

[%]

[mmHg]

[µMol/l]

[%]

Datasets

• 20 premature infants with need for intensive care

• MABP, SaO2, HbD and TOI measured simultaneously in the first days of life at University Hospitals Leuven

• HbD and TOI measured by NIRS (with NIRO300, Hamamatsu)

• Post menstrual age of 28.7 weeks (24-39)

• Weight : from 570 to 1470g

• Recording time : from 1h30 to 23h35

1. Introduction

2. Datasets

3. Methods

1. DC meth.

2. CPRT

3. Similarity meas.

4. Exp. results

5. Conclusion

Methods > DC methods

1. Introduction

2. Datasets

3. Methods

1. DC meth.

2. CPRT

3. Similarity meas.

4. Exp. results

5. Conclusion

• Correlation and (partial1) coherence coefficients to look at the direct concordance between signals MABP/HbD and MABP/TOI

• Frequency band of interest2 : 0 - 0.01Hz

• Sliding window approach3 : DC scores computed over 30-min epochs2

• SaO2 made constant4

______________________________________________________[1] Leuridan et al, ASME design eng div conf and exhibit on mech

vibration and noise, 1985. [2] Tsuji et al., Pediatrics, 2000.[3] Morren et al, Proc.23rd Annual Intern Conf IEEE Engineering in

Med and Biol Society, 2001. [4] De Smet et al, Proc. of the Belg. Day on Biomed. Eng. -

IEEE/EMBS Benelux Symp, 2006

Fig. : sliding window approach

Fig. : DC scores

Methods > CPRT

Problem : the DC score value differs from one time instant to another one : not handy to use

Solution : a measure that synthesizes the level of autoregulation of a patient for the whole recording time1,2 : the critical percentage of the recording time (CPRT)

____________________________________________________[1] Tsuji et al., Pediatrics, 2000.[2] Soul et al, Pediatric Research, 2007

1. Introduction

2. Datasets

3. Methods

1. DC meth.

2. CPRT

3. Similarity meas.

4. Exp. results

5. Conclusion

Fig. : CPRT

Methods > Similarity meas.

Aim : to prove that a signal may be replaced by another more handy one.

Particularly …

Question : may HbD (relative) be replaced by TOI (absolute) ?

Solution : derivation of similarity measures from the DC scores

Acronyms :DC score : direct concordance scoreHbD : cerebral intravasc. oxygenation.TOI : cerebral tissue oxygenation

1. Introduction

2. Datasets

3. Methods

1. DC meth.

2. CPRT

3. Similarity meas.

4. Exp. results

5. Conclusion

Fig. : linear regression

Experimental results

mCBS CB-CPRT

Mean of |r|

MSE

COH 0.76 0.81 0.027 0.0013

COR 0.63 0.71 0.043 0.0031

PCOH 0.70 0.78 0.041 0.0038

1. Introduction

2. Datasets

3. Methods

1. DC meth.

2. CPRT

3. Similarity meas.

4. Exp. results

5. Conclusion

Acronyms :• mCBS : mean correlation between DC score curves• CPRT : crit. percentage of the rec. time• CB-CPRT : correlation between CPRT curves• r : residual• MSE : mean square error

Conclusion

• Definition of a new synthesized measure of cerebral autoregulation : the CPRT

• Derivation of similarity measures proving that TOI can be used to assess impaired cerebral autoregulation in neonates

1. Introduction

2. Datasets

3. Methods

1. DC meth.

2. CPRT

3. Similarity meas.

4. Exp. results

5. Conclusion

Conference• Org. Committees• Fin. ContributorsGeneral Electric Company

Linde Gas

Philips Medical Systems

Gothia Medical AB

Bayer Schering Pharma

Unisense A/S

Kodak Carestream Health Sciences

Siemens Medical

Uppsala Kommun

Uppsala University

PhD grant• Fin. ContributorsResearch Council KULeuven

Flemish Government

Belgian Federal Science Policy Office

EU

ESA

• WorkgroupProf. Dr. Ir. S. Van Huffel

Prof Dr. G. Naulaers

Lic. J. Vanderhaegen

Thanks

to