Patent ID: 9649050
Date: 2017-05-16
CPC Classifications: A61B

Claim:
1. A method of estimating respiratory impedance with a system comprising a patient interface device, an excitation source operatively coupled to the patient interface, a ventilator, and one or more hardware processors, the method comprising: coupling the patient interface device to an airway of a subject who is using the ventilator to create a pneumatic system that includes the patient interface device and an airway of such a subject; generating, with the excitation source, pressure oscillations, flow oscillations, or volume of gas oscillations in the airway of the subject; determining, with the one or more hardware processors, the flow and pressure of the gas in the pneumatic system to produce a respective time series representing the flow and the pressure; transforming, with the one or more hardware processors, the respective time series to the time-frequency domain to create a transformed time series, wherein the transforming determines flow and pressure as a function of discrete time and different frequencies, wherein the different frequencies are a function of a frequency index and an effective width of a time-frequency filter, and wherein the transforming is based on the frequency index, the time frequency filter, and a weighting factor that is approximated by a windowing function of time, the weighting factor being a function of a time uncertainty, wherein the time series of measurements for flow and pressure are denoted q for the flow time series and for the pressure time series, wherein the different frequencies are give by f m =m/M, where m is the frequency index and M is the effective width of the time-frequency filter, i 2 =−1, and wherein the weighting factor w l is given by w l =e −(l/Δ ) , and Δ t is the uncertainty in time; estimating, with the one or more hardware processors, power of the flow and the pressure from the transformed time series; estimating, with the one or more hardware processors, respective cross spectra of the flow and the pressure based the transformed time series; estimating, with the one or more hardware processors, the respiratory impedance of the subject from the estimated power and the estimated cross spectra; and providing, with the one or more hardware processors, input to the ventilator based on the estimated respiratory impedance, the provided input causing an adjustment of one or more settings of the ventilator.