Method and device for monitoring and improving patient-ventilator interaction
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Abstract
Method and apparatus for non-invasively determining the time onset (Tonset) and end (Tend) of patient inspiratory efforts. A composite pressure signal is generated comprising the sum of an airway pressure signal, a gas flow pressure signal obtained by applying a gain factor (Kf) to a signal representing gas flow rate and a gas volume pressure signal obtained by applying a gain factor (Kv) to a signal representing volume of gas flow. Kf and Kv values are adjusted to result in a desired linear trajectory of composite pressure signal baseline in the latter part of the exhalation phase. The current composite pressure signal is compared with (i) selected earlier composite pressure signal values and/or (ii) value 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 rates of change. The differences obtained by the comparison are compared with selected threshold values. Tonset is identified when at least one of the differences exceeds the threshold values.
65 Citations
46 Claims
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20. A method for cycling off the inflation phase of a mechanical ventilator comprising:
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measuring the average interval between patient inspiratory efforts in a patient in a suitable number of elapsed breaths (TTOT) with said average being updated at suitable intervals; identifying onset of current inspiratory effort; monitoring time from said onset of inspiratory effort; and generating a signal that causes the ventilator to cycle off when time elapsed since onset of inspiratory effort exceeds a specified fraction of TTOT. - View Dependent Claims (21)
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22. A method for cycling off the inflation phase of a ventilator in pressure support ventilation comprising:
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measuring the interval between successive inspiratory efforts in a suitable number of elapsed breaths (TTOT); measuring inspiratory flow rate at specified times in those elapsed breaths which triggered ventilator cycles, said specified times corresponding to a specified fraction of the TTOT, measured from the onset of inspiratory effort of said each breath or from the trigger time of the ventilator; calculating the average of the flow values obtained at said specified times in said elapsed breaths; and generating a signal that causes the ventilator to cycle off when inspiratory flow in the current inflation phase decreases below said average flow value.
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38. A device for estimating a desirable duration of inflation phase of a ventilator, comprising:
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circuitry to identify inspiratory efforts of a patient; means to calculate the time difference between patient inspiratory efforts (patient TTOT); means for displaying a value corresponding to a specified fraction of patient TTOT, said specified fraction being a user input or a default value between 0.3 and 0.5. - View Dependent Claims (39, 40, 41)
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42. A device for determining the desirable inspiratory flow threshold for terminating inflation cycles in the pressure support ventilation mode comprising:
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circuitry for estimating desirable duration of inflation phase of the ventilator; means to measure inspiratory flow in recently elapsed breaths after said desirable duration has elapsed from the ventilator'"'"'s trigger time, or from the onset of inspiratory effort preceding triggered breaths, or from a specified point in between the latter two points; and means for displaying the value of said measured flow. - View Dependent Claims (43)
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Specification