Abstract: A fluid level sensor is disclosed having first and second vertically and horizontally nonoverlapping electrode plates for placing on a wall of a fluid container. Most preferably, the plates are also vertically spaced from each other. The capacitor plates are driven by a high frequency square wave. By forming nonoverlapping plates and driving them using a high frequency, the level of a fluid within the container, particularly viscous fluid, is more accurately detected. Control and detection circuitry is also disclosed to trigger an alarm if the fluid level drops below a critical level within the container.

Abstract: A transit time ultrasonic flow meter includes a pair of ultrasonic transducers transmitting an ultrasonic signal through a fluid flowing in a conduit and receiving the transmitted ultrasonic signal. An exclusive-OR (XOR) phase comparator then detects a difference in phase between the received ultrasonic signal and a reference signal having a selected phase shift (e.g., 0°, 90°, 180°, or 270°) with respect to the transmitted ultrasonic signal. Control circuitry selects the phase shift of the reference signal based on outputs of the XOR phase comparator in order to maintain the phase shifts detected by the XOR phase comparator within a range in which the comparator has relatively accurate detection (e.g., 45° to 135°). By adjusting the phase of the reference signal and thereby maintaining the XOR phase comparator in its relatively high accuracy region, the present invention enhances the accuracy of detection by the phase comparator.

Abstract: A clamping device for obstructing the flow of fluid through a tube is disclosed which may be electrically or manually actuated in response to an electrical signal from a condition detection means associated with the tube. The clamping device may also be actuated to compress the tube gradually, providing incrementally decreasing flow through the tube.

Abstract: A catheter set (10) is used in connection with a blood flow monitor and calibration system (80) to determine the compliance C of a vessel according to the equation C=dV2/ (PE-PA), where dV2 is the change in volume of the vessel created by the change in volume (e.g., deflation) of a displacement balloon (30) adjacent to a catheter (14), PE is an estimate of what the pressure measured by a pressure transducer (56) or a strain gage (78) would have been but for the change in volume of the displacement balloon at a particular time, and PA is the actual pressure measured by the transducer at the particular time. The determined compliance is more accurate than that obtained through thermal dilution procedures. The determined value of compliance C may then be used in calculation of blood flow. In addition, pulmonary vascular resistance and systemic vascular resistance may calculated through procedures and in equations using the determined compliance without directly measuring the pulmonary capillary wedge pressure.

Abstract: An extra corporeal support system has an inlet catheter which is positioned with its distal end in the right atrium or vena cava of the patient. A roller pump with an inlet pressure sensor positioned close to its inlet to sense the pressure in the inlet line which pumps the blood through the system to any output catheter positioned in the arterial system of the patient. The system has a shunt with blocking valves to block the flow automatically in the event of an unsafe condition. The system has a microprocessor based controller for automatic operation of the system components including a servo motor for driving the roller pump at a speed to precisely maintain the inlet pressure at a preselected point. The system includes a blood treatment device such as an oxygenator.

Abstract: An extracorporeal support system has an inlet catheter which is positioned with its distal end in the right atrium or vena cava of the patient. A roller pump with an inlet pressure sensor is positioned close to its inlet to sense the pressure in the inlet line which pumps the blood through the system to any output catheter positioned in the arterial system of the patient. The system has a shunt with blocking valves to block the flow automatically in the event of an unsafe condition. The system has a microprocessor-based controller for automatic operation of the system components including a servomotor for driving the roller pump at a speed to precisely maintain the inlet pressure at a preselected point. The system includes a blood treatment device such as an oxygenator. The roller pump has an axially adjustable head which is also removable.

Abstract: A retrograde perfusion system has a catheter and a driver to inject retroperfusate into the coronary sinus. The catheter has a balloon which is inflated and deflated to first occlude and then drain the coronary sinus. During occlusion, retroperfusate is injected under pressure by the driver which also operates the balloon all in accordance with a preselected program.