Example of respiratory tracing and ultrasonographic measurements during the 0 cmH2
O pressure support step (PS0)
(A) Sample recording of respiratory tracings during PS0: Pes, esophageal pressure; Pga, gastric pressure; Paw, airway pressure; Vi, respiratory flow; Pdi, transdiaphragmatic pressure. White area represents inspiration and gray area depicts expiration. (B) Ultrasonographic view of diaphragmatic excursion during breathing in B-mode (upper) and M-mode (lower). (C) Ultrasonographic view of diaphragm in the zone of apposition during inspiration (upper) and expiration (lower); the diaphragm is identified as a three-layer structure (non-echogenic central layer bordered by two echogenic layers, the peritoneum and the diaphragmatic pleurae) as indicated by yellow crosses.