Application of electrical impedance tomography in assessing diaphragmatic function

<bold>Purpose:</bold> This study used electrical impedance tomography to estimate the tidal volume and maximal inspiratory flows of each lung in patients with prolonged mechanical ventilation <bold>Materials and Methods:</bold> This observational study categorized the patients into unilateral diaphragmatic paralysis and non-paralysis groups based on chest ultrasound and computed tomography of the chest. During unassisted breath trials, the Dräger PulmoVista 500 was used to estimate the tidal volumes and maximal inspiratory flows of each lung for 5 to 10 minutes under steady state. <bold>Results:</bold> A total of nine patients were included in the analysis with four patients in the unilateral diaphragmatic paralysis group. Among the higher values of tidal volume and inspiratory flow recorded for each lung within the same patient, there was no significant difference between the two groups. Conversely among the lower values of tidal volume and inspiratory flow recorded for each lung within the same patient, there was a significant difference between the paralysis group and the non-paralysis group (tidal volume: 2.8 vs. 242.6 ml, p < 0.001; maximal inspiratory flow 45.8 vs. 298.6 ml/s, p < 0.0001). The difference in tidal volume and maximal inspiratory flow between bilateral lungs was significantly higher in the paralysis group than in the non-paralysis group (difference of tidal volume: 503.8 vs. 90.4 ml, p = 0.004; difference of maximal inspiratory flow: 546.8 vs. 88.8 ml/sec, p< 0.001). <bold>Conclusions:</bold> This pilot study illustrates the distinct respiratory physiology of each lung in cases of diaphragmatic paralysis. Electrical impedance tomography emerges as a promising diagnostic tool for illustrating local lung mechanics.