Preliminary Experimental Study about the Feasibility of Combining Pulsatile Cardiopulmonary Support System and a Membrane Oxygenator

Abstract

A cardiopulmonary support (CPS) device that incorporated a pneumatic ventricular assist device (VAD) and a membrane oxygenator was developed for the support of patients with profound heart and/or respiratory failure. This device has an advantage of being both a pulsatile assist device and membrane oxygenator. A “triple flow” regulator was included in this system to control the blood flow through the oxygenator. The purpose of this study was to clarify the efficacy of this system in supporting an animal model with combined cardiac and respiratory failure. In vitro tests showed 3.7 L/min of pump flow under 1.6 L/min of oxygen supply to the oxygenator even though there was a 50% clamp of a “triple flow” regulator with sufficient pulsatility. In 14 acute canine experiments, cardiogenic shock and acute respiratory failure were introduced by coronary ligation and mechanical hypoventilation simultaneously. The pump flow was maintaned at 1.95 - 0.6 L/min (average 1.2 L/min) and the driving pressure of the pump was controlled between 200 and 300 mmHg positive pressure and -20 to -50 mmHg negative pressure. The driving rate was fixed at 100 bpm and systolic/diastolic ratio was controlled between 35-50%. The canines were divided into control group (n=4) and pumped group (drained from the right atrium n=7, drained from the left atrium n=3). By using CPS system, flow and aortic pressure recovered to the initial baseline level. Without this support, the canine model could not maintain systemic circulation. In the group drained from right atrium, central venous pressure decreased with the device from 13.9 ± 2.4 to 5.6 ± 1.4 cm H₂O (p<0.01), returned to the initial level without this device (p<0.01). In the group drained from left atrium, pulmonary capillary wedge pressure decreased from 37.9 ± 4.6 to 20.8 ± 5.7 mmHg (p<0.01), and returned to the initial level without the device, arterial oxygen tension levels increased (p<0.01), and also arterial oxygen saturation levels recovered (p<0.01). The results suggest that the current model of the pulsatile CPS has a potential to support the animal model with combined cardiac and respiratory failure.