Also acquired with the linear probe, these clips depict the diaphragm of a patient with a C-spine injury following MVC while he is spontaneously breathing on a trach mask trial. Diaphragm assessment in the critically ill generally involves two measurements: Diaphragm excursion, and thickening. To measure thickening (what we’ve done here), use a high-frequency transducer to locate the diaphragm, which appears as a three-layered structure (diaphragmatic layers of pleural and peritoneal pleura, and a middle hyperechoic layer of muscle). From here use M-mode to take caliper measurements of diaphragmatic thickening at end inspiration, and end expiration. Thickening fraction = (end inspiratory thickness – end expiratory thickness)/end expiratory thickness. Diaphragm assessments in critically ill are very complex and will depend on the patients’ sedation levels, injuries, ventilatory support, etc. In this case, the fact that the diaphragm was moving, and thickening was helpful to rule out diaphragmatic paralysis due to high C-spine injury.
Until next time!
The POCUS Team