Abstract: A method and system for the extracorporeal treatment of blood to remove fluid from the fluid overloaded patient is disclosed that non-invasively measures an oxygen level in the venous blood. The oxygen blood level is used to detect when hypotension is about to occur in a patient. The oxygen level measurements are used as feedback signals. These feedback signals are applied to automatically control the rate of fluid extraction to achieve the desired clinical outcome and avoid precipitating a hypotensive crisis in the patient.

Abstract: A piston ventilator (10) includes a control circuit (80) for controlling the pressure to a patient circuit and thereby to the patient during patient inspiration. The control circuit (80) determines an error between the gas pressure and a set point pressure and in response, sends motor control signals to the motor (24) controlling the piston (22) to change the gas flow therefrom by the amount necessary so that the gas pressure substantially conforms to the set point pressure. More particularly, the motor control signals are a function of a proportion of the error, an integration of the error and the amount of leakage in the patient circuit at the current gas pressure. The set point is one of a plurality of set points on a pressure trajectory between a beginning pressure and a final target pressure during patient inspiration.

Abstract: A piston ventilator (10) includes a control circuit (80) for controlling the delivery of breathable gas to a patient circuit and thereby to the patient during patient inspiration. When operating in the volume control mode, the control circuit (80) determines the input volume of gas necessary to deliver a prescribed tidal volume to a patient while compensating for the pneumatic compliance of the ventilator (10) including the compliance of the cylinder (20) in which the piston (22) is positioned.