Figure 3
From: An automated and standardized neural index to quantify patient-ventilator interaction
Examples of patient-ventilator interaction and breathing pattern in three patients. (A- C), top (left) shows a raw tracing of electrical activity of the diaphragm (EAdi) and ventilator pressure (PV). Mid (left), pie-diagram shows the relative distribution of events. Bottom (left), intra-breath patient-ventilator interaction with synchrony (inside the box) and dyssynchrony (outside the box), expressed as percentage of the total number of events. Right, histograms of ventilator and neural respiratory frequency, tidal volume, PV (above positive end-expiratory pressure (PEEP)), and EAdi. (A) Raw tracings in the top panel show clearly distinguishable EAdi and PV waveforms. The pie-diagram shows that almost all breaths (close to 91%) are synchronous. It can be seen that the majority of signals appear inside the box in the upper right quadrant, indicating synchronized assist with a slightly delayed onset and termination of assist relative to the EAdi. The histograms (top to bottom on right side) show that frequency of ventilator-delivered breaths (FV) and of neural (patient) breaths (FN) are stable between 20 to 25 breaths/minute. Tidal volume was 0.4 to 0.5 l at an assist level of 12 to 14 cm H2O above PEEP. EAdi is concentrated in the range of 15 to 20 μV. (B) EAdi and PV waveforms are distinguishable, but it is clear that neural efforts occur more frequently than ventilator breaths. The pie-diagram reveals 50% of the EAdi breaths were not assisted, and 2% of assist occurred without EAdi; 48% of the signals appear in the upper left quadrant outside the box, indicating substantial delays for both onset and termination of assist relative to EAdi. The histograms show that FV occurs at 5 to 15 breaths/minute, whereas FN demonstrates two peaks at 10 and 35 breaths/minute. Tidal volume is 0.4 to 0.6 l at an assist level of 12 to 14 cm H2O above PEEP. EAdi ranges from 5 to 20 μV. (C) The waveforms show that EAdi is infrequent and almost non-distinguishable, whereas PV is clearly distinguishable and frequent. The pie-diagram indicates a 91% of assist without EAdi, 2% of EAdi without assist and only 7% of breaths land inside the box. The histograms show that FV is stable at 14 to 16 breaths/minute, whereas FN is either very low (few breaths) or very high (>60 breaths/minute). Tidal volume is 0.3 to 0.4 l at an assist level of 12 to 14 cm H2O above PEEP. EAdi shows that some breaths reach 12 to 14 μV, but the majority is lower than 2 μV.