PMC4823850_01
Chest radiograph (a) and chest computed tomography (b) at hospital admission
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Fig1
When he presented to the respiratory medicine clinic, he had a fever of 39  C and infiltration was observed in the right lung field on chest radiographs (Fig. 1).
Chest radiographs at ICU admission (a) and at weaning from ECMO (b)
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Fig2
On day 18, the patient developed pneumomediastinum and pneumothorax and because acute respiratory distress syndrome developed after chest drainage, the patient was transferred to our intensive care unit (ICU) on day 20 (Fig. 2a). As the chest radiographic findings improved and the oxygenation during a minimal pump flow test met the weaning criteria for ECMO 7 days later (day 26), the patient was successfully weaned from V-V ECMO (Fig. 2b). PSV is a decelerating, triangular pattern (Fig. 3a), while that of NAVA is sinusoidal shape (Fig. 3b) that is identical to the shape of the muscle tension generated by the diaphragm, suggesting the better synchrony during NAVA. Patient-ventilator synchrony improved considerably after the introduction of NAVA, as shown in Fig. 2.
Ventilator graphics during flow trigger (a) and NAVA (b). These two figures were obtained just after conversion from assist/control mode. Top pressure-time curve, mid-top flow-time curve, mid-bottom tidal volume-time curve, bottom electromyography of diaphragm. Dashed line termination of inspiration guided by electromyography of diaphragm. Improved synchrony after initiating NAVA is obvious compared with SIMV. NAVA neurally adjusted ventilatory assist, SIMV synchronized intermittent mandatory ventilation. Single asterisk autotriggering, double asterisks premature cycling
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Fig3
Concurrent analysis of electromyography of the diaphragm and airway pressure and inspiratory flow waveforms clearly demonstrated auto triggering, trigger delay for the diaphragm contraction, and premature cycling in FT (Fig. 3a). Initiation and termination of inspiration were well synchronized, which decreased the respiratory rate from 48 to 30 breaths/min and increased the minute volume (Fig. 3b). PSV is a decelerating, triangular pattern (Fig. 3a), while that of NAVA is sinusoidal shape (Fig. 3b) that is identical to the shape of the muscle tension generated by the diaphragm, suggesting the better synchrony during NAVA. Patient-ventilator synchrony improved considerably after the introduction of NAVA, as shown in Fig. 2. However, in our patient, we saw a dorsal shift of ventilation with the higher supporting pressure during NAVA, compared with PSV (Figs. 3 and 5).
Changes in regional ventilation and global tidal impedance measured by electrical impedance tomography. Figure shows values during flow trigger (FT, left. PSV 18 cmH2O and expiration cycling time 25 %, PEEP 7 cmH2O) and NAVA (right. Gain 1 cmH2O/muV, PEEP 7 cmH2O). Numbers on the bar indicate the proportion of ventilation distribution in each lung region. Global tidal impedance increased 1.32 times after NAVA. NAVA neurally adjusted ventilatory assist, PEEP positive end-expiratory pressure
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Fig4
Global tidal impedance variation, which reflects tidal volume, was 1.32 times higher with NAVA (gain 1 cmH2O/muV, PEEP 7 cmH2O) compared with SIMV (Fig. 4).
Center of ventilation (COV) in each lung calculated by electrical impedance tomography. Figure shows values during flow trigger (FT, right) and NAVA (left). The sum of ventilation-related impedance change in each lung slice is calculated and presented as a bar in the histograms. Horizontal lines indicate the position of COV. COV shifted to the dorsal region during NAVA in the right lung. FT flow trigger, NAVA neurally adjusted ventilatory assist, COV center of ventilation
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Fig5
The center of ventilation also shifted to the dorsal region (from 53 to 43 % in the right lung and from 47 to 44 % in the left lung) during NAVA (Fig. 5). However, in our patient, we saw a dorsal shift of ventilation with the higher supporting pressure during NAVA, compared with PSV (Figs. 3 and 5).