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

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 • Introduction • Datasets • Methods • DC meth. • CPRT • Similarity meas. • Exp. results • Conclusion • Problem : impaired cerebral autoregulation • Solution : detect ΔHbDconcordant with • ΔMABP (with ΔSaO2=0)1 • But … • Problem :HbD (=HbO2-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. • SaO2 : arterial oxygen saturation • TOI : cerebral tissue oxygenation • _____________________________________________________ • [1] Tsuji et al., Pediatrics, 2000.

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

4. Datasets • Introduction • Datasets • Methods • DC meth. • CPRT • Similarity meas. • Exp. results • Conclusion • 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

5. Methods > DC methods • Introduction • Datasets • Methods • DC meth. • CPRT • Similarity meas. • Exp. results • 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

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 time1,2 : the critical percentage of the recording time (CPRT) ____________________________________________________ [1] Tsuji et al., Pediatrics, 2000. [2] Soul et al, Pediatric Research, 2007 • Introduction • Datasets • Methods • DC meth. • CPRT • Similarity meas. • Exp. results • 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 • Introduction • Datasets • Methods • DC meth. • CPRT • Similarity meas. • Exp. results • Conclusion

11. Fig. : linear regression

12. Experimental results • Introduction • Datasets • Methods • DC meth. • CPRT • Similarity meas. • Exp. results • 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 • Introduction • Datasets • Methods • DC meth. • CPRT • Similarity meas. • Exp. results • 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

14. Thanks to