1. 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

2. Introduction Problem : impaired cerebral autoregulation Solution : detect ΔHbD concordant with ΔMABP (with ΔSaO 2 =0) 1 But … Problem : HbD (=HbO 2 -HbR) is not an absolute value Solution : prove that TOI may replace HbD for measurement of impaired cerebral autoregulation Acronyms : MABP : mean arterial blood pressure HbD : cerebral intravasc. oxygenation. SaO 2 : 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

3. Fig. : signals of interest [%] [mmHg] [µMol/l] [%]

4. Datasets 20 premature infants with need for intensive care MABP, SaO 2, 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

5. Methods > DC methods 1.Introduction 2.Datasets 3.Methods 1.DC meth. 2.CPRT 3.Similarity meas. 4.Exp. results 5.Conclusion Correlation and (partial 1 ) coherence coefficients to look at the direct concordance between signals MABP/HbD and MABP/TOI Frequency band of interest 2 : 0 - 0.01Hz Sliding window approach 3 : DC scores computed over 30-min epochs 2 SaO 2 made constant 4 ______________________________________________________ [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

6. Fig. : sliding window approach

7. Fig. : DC scores

8. 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 time 1,2 : 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

9. Fig. : CPRT

10. 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 score HbD : 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

11. Fig. : linear regression

12. Experimental results mCBSCB- CPRT Mean of |r| MSE COH0.760.810.0270.0013 COR0.630.710.0430.0031 PCOH0.700.780.0410.0038 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

13. 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

14. Conference Org. Committees Fin. Contributors General 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. Contributors Research Council KULeuven Flemish Government Belgian Federal Science Policy Office EU ESA Workgroup Prof. Dr. Ir. S. Van Huffel Prof Dr. G. Naulaers Lic. J. Vanderhaegen Thanks to