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A preliminary investigation into the occurrence of cavitation in the cardiopulmonary bypass circuit / by Cameron N. Bryan.

by Bryan, Cameron N.

Cardiopulmonary bypass -- Adverse effects

Blood -- Circulation, Aritificial

Extracorporeal Circulation

Fluid mechanics

84 leaves : ill. ; 28 cm.

Advisor: Dr. Vincent Canino.

Committee members: Dr. Larry Fennigkoh, Scott Brown.

Introduction -- Fluid mechanics of cavitation -- Cavitation in biological systems -- Modeling cavitation number -- Modeling bubble growth -- Modeling bubble collapse -- Conclusion -- Bibliography -- Appendix 1- Additional equations 2- Cavitation number data 3- Peak pressure data 4- Bubble collapse data 5- Cavitation number dependent upon tubing diameter & flow 6- Bubble growth data 7- Gaussian distribution data for bubble count 8- Bubble collapse time dependent upon external pressure 9- Pressure conversion tables 10- Bubble size dependent upon tubing diameter.

The use of smaller venous cannulas, increased utilization of peripheral cannulation sites, and the desire to reduce the cardiopulmonary bypass (CPB) circuit, potentially create clinical situations where venous return is reduced. Adequate venous return is crucial for a successful and uneventful surgical outcome.

Two different techniques have been used to increase venous return; they are kinetic-assisted (KAVD) and vacuum-assisted venous return (VAVD). In recent years, Kuntz, Jones, and others have reported measuring an increase in the number of air emboli that are being detected (by Doppler ultrasound) distal to the arterial line filter, specifically when VAVD is utilized. One potential cause of these bubbles is cavitation.

This thesis will review the science of cavitation and bubble dynamics and will attempt to determine if the mathematical equations used to predict cavitation in water could be used for blood. Additionally, this thesis will identify the characteristics of blood which may increase or decrease the likelihood of cavitation to occur in blood.

In conclusion, the cavitation number equation predicts that reference pressures and flow rates, used clinically, is likely to result in cavitation occurring in blood, The bubble growth equation predicts that bubbles are being formed which are small enough to pass through the arterial line filter. The bubble collapse equation predicts a small time interval is necessary to completely collapse a bubble; although during the cycle of growth and collapse a bubble may remain long enough to potentially travel a large distance through the CPB circuit.

Blood has many interent properties, which may have a large influence on the occurrence of cavitation. By using the CPB circuit, non-natural conditions such as VAVD and hypothermia, can be applied to blood which increases the likelihood of cavitation occurrence. Any bubble which passes through the arterial line filter and enters into the patients' circulation may result in a variety of detrimental effects on the patient.

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