Non-invasive diagnostics for ventricle assist device

摘要

A circulatory assist system has a pump with a motor coupled to rotate the pump at a selectable speed. A controller drives the motor at a target speed and collects blood flow measurements during operation of the pump. An impaired flow condition is identified when a plurality of successive blood flow measurements are between an expected minimum flow and a low flow threshold, such that the low flow would necessitate issuing an alert. During the impaired flow condition, it is detected whether an inflow obstruction exists by determining whether a reduction in speed of the pump is correlated with a predetermined increase in the blood flow measurements. If the inflow obstruction is detected, then the speed of the pump is further reduced to further increase the blood flow measurements.

主权项

1. A method of controlling a pump motor in an assist device for pumping blood of a patient, comprising the steps of:
monitoring an actual pump flow value as the assist device pumps blood to the patient; determining an expected minimum pump flow value corresponding to nominal pump operation for the monitored speed and current flow; when the actual pump flow value is greater than the expected minimum pump flow value, setting a target speed of the pump motor according to predetermined criteria; when the actual pump flow value is less than the expected minimum pump flow value for at least a first diagnostic wait time, then entering a pump flow diagnostic state; wherein the pump flow diagnostic state is comprised of:
entering a low pump flow state if the actual pump flow value is less than a low flow threshold for at least a low flow wait time, wherein the low flow threshold is less than the expected minimum pump flow value, and wherein the low pump flow state includes generating a low flow warning;entering a no pump flow state if the actual pump flow value is less than a no flow threshold for at least a no flow wait time, wherein the no pump flow state includes generating a no flow warning, wherein the no flow threshold is less than the low flow threshold, and wherein the no flow wait time is less than the low flow wait time; andentering an obstructed flow diagnostic state if the actual pump flow value is less than the expected minimum pump flow value for at least an obstruction diagnostic wait time, wherein the obstruction diagnostic wait time is greater than the low flow wait time; and wherein the obstructed flow diagnostic state is comprised of:
selectably modifying the target speed of the pump motor and monitoring the resultant actual pump flow value;detecting an inflow obstruction if a reduction in target speed is correlated with a predetermined increase in the resultant actual pump flow value; andif an inflow obstruction is detected, then selectably decreasing the target speed to a new target that substantially maximizes the actual pump flow value.