AUTHOR=Widing Carl Hannes , Pellegrini Mariangela , Larsson Anders , Perchiazzi Gaetano 

TITLE=The Effects of Positive End-Expiratory Pressure on Transpulmonary Pressure and Recruitment–Derecruitment During Neurally Adjusted Ventilator Assist: A Continuous Computed Tomography Study in an Animal Model of Acute Respiratory Distress Syndrome

JOURNAL=Frontiers in Physiology

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2019.01392

DOI=10.3389/fphys.2019.01392

ISSN=1664-042X

ABSTRACT=<sec><title>Background</title><p>Whether spontaneous breathing (SB) should be used in early acute respiratory distress syndrome (ARDS) is questioned because it may cause ventilator-induced lung injury (VILI) by tidal high strain/stress and recruitment/derecruitment (R/D). However, SB has shown beneficial effects when used appropriately. We hypothesized that high levels of positive end-expiratory pressure (PEEP), during assisted SB, would prevent tidal R/D, reducing ventilatory variation and respiratory rate while potentially increasing transpulmonary pressure (<italic>P</italic><sub>TP</sub>). The aim was to test this hypothesis in experimental mild ARDS during continuous SB using neurally adjusted ventilator assist (NAVA) and uninterrupted computed tomography (CT) exposure.</p></sec><sec><title>Methods</title><p>Mild experimental ARDS (PaO<sub>2</sub>/F<sub>i</sub>O<sub>2</sub>-ratio of 250) was induced in anesthetized pigs (<italic>n</italic> = 5), ventilated using uninterrupted NAVA. PEEP was changed in steps of 3 cmH<sub>2</sub>O, from 0 to 15 and back to 0 cmH<sub>2</sub>O. Dynamic CT scans, ventilatory parameters, and esophageal pressure were acquired simultaneously. <italic>P</italic><sub>TP</sub> and R/D were calculated and compared among PEEP levels.</p></sec><sec><title>Results</title><p>When increasing PEEP from 0 to 15 cmH<sub>2</sub>O, tidal R/D decreased from 4.3 ± 5.9 to 1.1 ± 0.7% (<italic>p</italic> &lt; 0.01), breath-to-breath variability decreased, and <italic>P</italic><sub>TP</sub> increased from 11.4 ± 3.7 to 29.7 ± 14.1 cmH<sub>2</sub>O (<italic>R</italic><sup>2</sup> = 0.96).</p></sec><sec><title>Conclusion</title><p>This study shows that injurious phenomena like R/D and high <italic>P</italic><sub>TP</sub> are present in NAVA at the two extremes of the PEEP spectrum. Willing to titrate PEEP to limit these phenomena, the physician must choose the best compromise between restraining the R/D or <italic>P</italic><sub>TP</sub>.</p></sec>