Control, monitor and alarm system for clinical application of a membrane oxygenator

Membrane oxygenators, now commercially available, are undergoing clinical trials as long-term (days) respiratory support devices for patients in potentially reversible respiratory failure. However, these devices must be used in an integrated system of controls, monitors and alarms if they are to be reliable and easy to operate in the clinical environment. This paper describes such a system. The tubing circuits for blood and for oxygen are described first. Next, details of the blood pump controls are presented. The system features servo control of pump speed to match blood inflow, and deactivation of the pump in the case of excessive output pressure. Gas circuit controls are described which allow the independent adjustment of both oxygen flow through the gas phase of the membrane lung and oxygen pressure developed at the inlet gas port. Audible alarms are provided for low blood inflow to the system, excessive blood outflow pressure, changes in oxygen flow and failure of the electric power supply to the system. In addition to pressure and flow monitors in the blood and gas circuits, blood oxygen saturation is continuously monitored at both input and output of the system. The membrane oxygenator system has proved to be reliable and easy to operate in both animal and human long-term perfusions.