Study on Cerebral Autoregulation in Premature Infants Using Tissue Oxygenation Measurements

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

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