Instrumentation based on measurement of Blood pH

1. Blood pH Measurement SuhasDeshpande EE506 Dr. Druzgalski

2. Outline pH Blood and pH pH Monitoring Glass Electrodes Metal-metal oxide electrodes pH sensitive FETs Conductimetric pH sensors Fiber optic pH sensors Temperature dependence Calibration Model G pH meter (Beckman Coulter, Inc. 1936) http://www.ph-meter.info/pH-meter-history

3. pH Defined Chemically: measure of acidity or basicity of a fluid Physically: Measure of concentration of H+ ions Mathematically: pH = -log10[H+] Technically: Power or Potential of hydrogen ions in the fluid.

5. Diagnosis of patients in ICU

6. Major surgeries like open heart surgery

7. Diagnosis of effect of a particular drug on the patientBlood pH is very tightly regulated in human body generally lies between 7.3-7.5 Acute changes in blood pH induce powerful regulatory effects at the level of the cell, organ, and organism The pH of blood plasma and various other body solutions is tightly regulated variables in human physiology

8. pH monitoring

9. pH measurement Glass Electrodes Metal-metal oxide electrodes pH sensitive FETs Conductimetric pH sensors Fiber optic pH sensors

10. Glass Electrodes EMF is developed between the measuring electrode and reference electrode Time consuming Needs blood sample to be taken www.ph-meter.info/pH-electrode-construction

11. Metal-metal oxide electrodes Working on similar principle Rhodium-iridium can be used as electrode Chemical equilibrium between salt-salt solution cause potential between the electrodes Easy to miniaturize and CMOS compatible

12. Comparing MMO Electrodes

13. pH sensitive FETs Based on MOSFET device can be manufactured using CMOS technology Various gate materials used SiO2, Si3N4, Al2O3

14. Compare different ISFETs

15. Conductimetric sensors Based on the change in the conductivity upon contact with changing pH Polymers such as Polyaniline (PANI) show wide range of conductivities with varying pH for different dopings.

16. Conductimetric sensors

17. Fiberoptic pH sensors Safe small can be placed in patient’s arteries Based on absorption or fluorescence In-vitro analysis makes continuous monitoring possible Indicator dye Phenol red can be used for the range 7.0-7.5 http://www.oceanoptics.com/Products/phsensor.asp

18. Optical pH Sensor System Two LEDs with different wavelenths Florescence measured using photo detector Amount of florescence determines the pH Result of optical sensor linear, with max error of 0.18 and avg error 0.061

19. Comparing different electrodes

20. Temperature dependence Temperature dependence of pH increases with increase in bascicity For basic solutions pH depends on autoprotolysisof water which is temperature dependent

21. Calibration Two point calibration pH = (6.0,8.0) Signal pH = 6.0 brought to base zero Slope(gain) adjusted using ∆pH = 2.0 (i.e 8.0-6.0) Base zero adjusted to pH signal = 6

22. Industrial pH Meters Thermo-Fisher: http://www.thermofisher.com/global/en/home.asp Siemens (Tel.: 1-800-SIEMENS) http://www.usa.siemens.com/entry/en/

23. References http://www.ph-meter.info www.ph-meter.info/pH-electrode-construction http://ccforum.com/content/4/1/6 http://www.oroboros.at/index.php?id=mipnetanalyzer W. Vonau,"pH Monitoring: a review," J Solid State Electrochem (2006) 10: 746–752 Danny O’Hare, Kim H.Parker, C.PeterWinlove,"Metal–metal oxide pH sensors for physiological application," Medical Engineering & Physics 28 pp 982–988, 2006 Peter Kurzweil, "Metal Oxides and Ion-Exchanging Surfaces as pH Sensors in Liquids: State-of-the-Art and Outlook," Sensors 2009 E. I. Gill, A. Arshak, K. Arshak and O. Korostynska, "Investigation of Thick-Film Polyaniline-Based Conductimetric pH Sensors for Medical Applications," Sensors Journal, IEEE, vol. 9, pp. 555-562, 2009. N. Sheppard, "Microfabricatedconductimetric pH sensor," Sensors and Actuators.B, Chemical, vol. 28, pp. 95, 1995. T. Lumsden, "The PB3300 intraarterial blood gas monitoring system," J. Clin. Monit., vol. 10, pp. 59, 1994. B. Palan, K. Roubik, M. Husak and B. Courtois, "CMOS ISFET-based structures for biomedical applications," Microtechnologies in Medicine and Biology, 1st Annual International, Conference on. 2000, pp. 502-506, 2000. A. Sohanghpurwala, "Optical replacement of pH electrode," IEEE Sensors Journal, vol. 9, pp. 219, 2009.