Comparative study of rigid vs flexible pneumatic artificial blood pumps

For HR in the range of 70--110 beats/min, and same driving conditions, the pump with rigid housing produced a maximum of 15% greater CO than that with the soft housing, against an arterial pressure of 125/75 mm Hg. All 3 pumps exhibited greater sensitivity in function curves for HR in the range of 90--110 beats/min. The greatest sensitivity point in the function curve, for the rigid housing pump was found to be independent of HR change in the range of 90--110 beats/min. However, with an increase in HR the function curves shifted to the right in the case of soft housing pumps. In other words, greater atrial pressure was required to obtain the same CO with an increase in HR. The linear relationship found between CO and HR in flexible and soft housing pumps was very advantageous for controlling CO, whenever such change was required. In all 3 hearts there was a decrease in pulse pressure with an increase in HR. The decrease in pulse pressure was primarily due to the increase in diastolic pressure, while systolic pressure remained almost constant at all HRs. Since these experiments were conducted in a test circulatory system using an aqueous-glycerin solution, information on the degree of hemolysis was not addressed in this report.