Determination of Time Delay Using Cross Correlation
Original Publication Date: 2002-Sep-01
Included in the Prior Art Database: 2003-Jul-23
As can be seen from the insert of Fig.1 that shows indetail the ringed region, the output from the expira-tion pressure sensor is delayed with respect to thatfrom the inspiration pressure sensor by a time, t d.This time, t d is determined in a digital data processorfrom a cross correlation of the two curves (1,2).Usefully, data processing may be limited to a timewindow during which large pressure changes areexpected to be measured, for example at the begin-ning (t 0 ) or the end (t 1 ) of an inspiration phase. Thedata processing system employed to perform thecross-correlation is therefor preferably operablyconnected to the ventilator so as to collect and/oranalyse data from the pressure sensors in dependenceof signals from the control system of the ventilatorthat are provided in a timed relation with the opera-tion of the ventilator.
Determination of Time Delay UsingCross Correlation
Idee: Åke Larsson, SE–Solna
Pressure sensors are usually found in both the inspi-ration and the expiration branches of the gas flowcircuit in a patient ventilator system. At any time inthe breathing cycle there will exist a time delay be-tween pressure sensed by the different sensors. Forexample, during an inspiration phase the expirationsensor will measure a signal that is delayed withrespect to that measured by the inspiration sensor. Aventilator is typically regulated using the combinedcontemporaneous outputs of these sensors, w...