Noninvasive Neurally Adjusted Ventilator Assist Ventilation in the Postoperative Period Produces Better Patient-Ventilator Synchrony but Not Comfort

Figure 3

Presented are three different screenshots of ventilator tracings; tracing on top always EAdi, second tracing flow, third tracing pressure, fourth tracing ventilator signal. The axes are as follows: EAdi in microvolt, flow in liters per minute, pressure in mbar, ventilator dichotomous off/on, -axes: time in milliseconds. Values are spared intentionally because this figure should be seen as a schematic rather than a visual representation of study data. (a) Perfect neuronal triggering, the ventilator cycles on (red vertical line) at exactly the same time as the increase in EAdi signal tracing (green broken vertical line) happens; times not marked because in this perfectly triggered breath there is no delay. (b) Visual presentation of the concept of “EAdi true”. The time point marked with the black double-arrow is the moment when a decrease in pressure happens but the EAdi tracing does not show an increase, rather does it show the plateau mentioned in the text, representing a blacked out ECG signal (green arrow). During the plateau inspiratory activity of the diaphragm cannot be detected. The start of inspiration is therefore not where the EAdi tracing starts to rise, but rather where a drop in pressure tracing during the EAdi-plateau is detected. This is where the EAdi-signal would rise, if ECG “disturbance” had not happened. EAdi-delay: black double-arrow; regular ventilator delay: red arrows; purple area: negative pressure swing. (c) Pneumatically triggered breath during PSV, visual presentation of inspiratory and expiratory delay. The beginning of the EAdi tracing representing the start of inspiration is marked by the vertical broken green line. The start of ventilator activity (red vertical line) happens belated relative to EAdi but perfectly in time in regard to PSV criteria. Without the EAdi tracing this inspiratory delay cannot be detected. The end of ventilator activity (black vertical line) happens before EAdi tracing has reached the off-cycling criterion (vertical broken red line, 70% EAdi-peak); at this moment, the patient’s diaphragm was still activated denoting that inspiration was still ongoing. Expiratory delay is marked by red arrowhead.

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