Patent ID: 7484508

Claim:
A method for detecting the onset of inspiratory effort (T onset ) in a patient on mechanical ventilation, comprising the steps of: (a) monitoring airway pressure, rate of gas flow, and volume of gas flow of the patient; (b) applying a gain factor (K f ) to the signal representing rate of gas flow to convert the gas flow signal into a gas flow pressure signal; (c) applying a gain factor (K v ) to the signal representing volume of gas flow, also to convert the gas volume signal into a gas volume pressure signal; (d) generating a composite pressure signal comprising the sum of airway pressure signal, gas flow pressure signal, and gas volume pressure signal, with all signals having suitably adjusted polarity; (e) adjusting K f and K v to result in a desired linear trajectory of composite pressure signal baseline in the latter part of the exhalation phase; (f) comparing (i) current composite pressure signal values with selected earlier composite pressure signal values, and/or (ii) current composite pressure signal values with values expected at current time based on extrapolation of composite pressure signal trajectory at specified earlier times, and/or (iii) the current rate of change in the composite pressure signal with a selected earlier rate of change in the composite pressure signal; (g) comparing differences obtained from such comparison(s) made in step (f) with selected threshold values; and (h) identifying T onset when at least one of said differences exceeds said threshold values.