Ultrasound Assessment of Diaphragmatic Motion in Subjects With ARDS During Transpulmonary Pressure-Guided PEEP Titration

We aimed to investigate the effects of incremental PEEP titration in patients with ARDS on regional diaphragmatic motion with bedside ultrasound. Dorsal diaphragmatic excursion (DDE) and ventral diaphragmatic excursion (VDE) were measured using anatomic M-mode ultrasonography of the right hemidiaphragm as PEEP was randomized to -6, -3, +3, and +6 cm H O from baseline to achieve a positive transpulmonary pressure. Inter-operator variability of DDE was assessed in 10 separate subjects. A total of 14 subjects ventilated for ARDS were enrolled. Subjects had a mean age of 54 ± 12 y, mean P /F = 137 ± 54 mm Hg, and mean sequential organ failure assessment (SOFA) score = 14 ± 1). Transpulmonary pressure, DDE, and DDE/VDE ratio increased with incremental PEEP titration (-1.15 cm H O vs 3.63 cm H O, < .001; 4.9 mm vs 8.2 mm, < .001; and 62% vs 93%, < .001, respectively). When transpulmonary pressure became positive, a visual increase in DDE and DDE/VDE ratio 0.60 to 0.93 was observed (from 0.48 cm to 0.82 cm, R = 0.87, = .02; and R = 0.93, = .006, respectively). There was high agreement in DDE measurements between 2 ultrasonographers (intra-class correlation 0.987, < .001). DDE was affected by incremental PEEP titration toward a positive transpulmonary pressure. The ultrasound assessment using anatomic M-mode allowed for specific measurement of regional diaphragmatic excursion. This pattern of motion in the dependent regions of the diaphragm during PEEP titration in subjects with ARDS achieving a positive transpulmonary pressure may reflect a potential target for future studies in the bedside assessment for lung recruitment. (Clinical Trials.gov registration NCT02463773.).