22 May 1997 Measurement of cardiac output using near-infrared heating of blood
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Abstract
Thermodilution-based cardiac output measurements are made using iced saline or blood heated by resistive heating as a dilutable indicator. Because near-infrared irradiation penetrates sufficiently deeply into blood, it can safely deposit up to six times the energy of a resistive heater, improving the accuracy of the measurements while continuously monitoring cardiac output. We have developed a prototype system using 980 nm diode lasers to irradiate blood through a diffuser. This system was tested using an optical blood phantom and was compared to iced-saline injection and resistive heating. Three flow estimates were made at each of 18 combinations of stroke rate, stroke volume, and systole/diastole ratios. Accuracy was determined by the quality of the fit between the estimated flows and the actual flow. Reproducibility was determined by the normalized standard deviation. Results: Measurements made by saline injection were the most accurate (R2 equals 0.982) and reproducible (NSD equals 2.8%). Power limitations on the resistive heating to ensure a safe blood temperature limited its accuracy (R2 equals 0.537) and reproducibility (NSD equals 18.1%). Laser-based heating showed reasonable accuracy and reproducibility (R2 equals 0.950, NSD equals 7.8%). Laser heating thus represents a potentially more accurate alternative to saline injection for cardiac output measurement than does resistive heating.
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Michael G. Curley, Michael G. Curley, Patrick S. Hamilton, Patrick S. Hamilton, Joseph T. Walsh, Joseph T. Walsh, } "Measurement of cardiac output using near-infrared heating of blood", Proc. SPIE 2970, Lasers in Surgery: Advanced Characterization, Therapeutics, and Systems VII, (22 May 1997); doi: 10.1117/12.275080; https://doi.org/10.1117/12.275080
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