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An investigation into the production of air microemboli during varying pulsatile flow parameters / Holly A. Estill.

by Estill, Holly A.

Blood -- Circulation, Artificial

Microcirculation

Cardiopulmonary bypass -- Adverse effects

142 leaves : ill. ; 29 cm.

Thesis advisor(s): Dr. Vincent Canino.

Committee members: Dr. Ronald Gerrits, Dr. Larry Fennigkoh.

Introduction -- Background -- Materials and methods -- Results -- Discussion -- Appendices A: Raw data from preliminary plasmalyte experiment B: XY scatter plots from preliminary experiment C: Raw data from experiment with bovine blood D: Pressure analysis data from experiment with bovine blood E: Correlation tables for analysis of bovine blood experimental data F: Multiple linear regression tables for analysis of bovine blood experimental data G: XY scatter plots of experimental raw data with bovine blood.

Pulsatile flow may not be an entirely new development in the arena of cardiopulmonary bypass; however, technology has improved over the years to create more efficient and less rheologically detrimental methods of producing pulsatile blood flow. Many different papers have been written regarding the potential positive and negative effects of pulsatile flow. One area that has yet to be examined with regard to pulsatile flow is the possibility of air microemboli development from the use of varying pulsatile flow techniques. This paper examined the possibility of air microemboli development when a roller head pump was used to create pulsatile flow. Roller head pumps create pulsatile flow by increasing and decreasing the revolutions per minute of the pump head and inherently creating larger pressure drops that could pull air out of solution at the arterial pump head inlet. If large amounts of air are able to be pulled out of solution at the pump head inlet, there would be a threat of air microemboli being passed onto the patient, which could result in catastrophic post operative neurological deficit.

To examine the relationship between air microemboli development and pulsatile blood flow, an experiment was developed that included measuring air microemboli at four different circuit locations on a cardiopulmonary bypass circuit (arterial pump inlet, oxygenator inlet, oxygenator outlet, and arterial filter outlet). The circuit that was utilized in this experiment was an SX25 Terumo Oxygenator in conjunction with a standard Terumo X-Coated Tubing Pack. During the experiment the following pulsatile flow parameters were varied to determine if there was a relationship between pulsatile flow parameters and air microemboli production at different locations within the CPB circuit: base flow, continuous flow rate, and frequency. Instantaneous pressure was also measured at the four points within the circuit simultaneously with the bubble measurements. The instataneous pressure measurements were then used to calculate an RMS pressure, average pressure, and minimum pressure for each of the 360 trials. The objective was to find a correlation between pressure and air microemboli production in the cardiopulmonary bypass circuit.

The results of the experiment did not show any significant relationship between Base Flow and air microemboli development, Continuous Flow Rate and air microemboli development or Frequency and air microemboli development. The results further did not find a correlation between the minimum, average or RMS pressure and air microemboli production within the circuit. It can therefore be concluded from the results of this experiment that utilizing pulsatile flow settings in the range of base flow 0-50%, continuous flow rate 4.5-6.5 L/min., and frequency of 60-80 BPM will not produce significant amounts of air microemboli at the Arterial Pump Inlet, Oxygenator Inlet, Oxygenator Outlet, or Arterial Filter Outlet.

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