Fig. 1

Representative ultrasound of the diaphragm. Diaphragm at total lung capacity (a) and functional residual capacity (b). The diaphragm (D, white bidirectional arrows) is the 3-layered structure situated deep to the intercostal (IC) muscles spanning two ribs; it is identified as the last set of parallel lines, with the pleural and peritoneal membranes overlying the less echogenic muscle. We calculated a mean of three points using the IMT software: the center of the diaphragm thickness, and two surrounding points on either side (each 10 mm from the center of the diaphragm thickness)