Echodensity histograms of controls and patients at ICU admission. The histograms (left graph) represent the average proportion of pixels (percentage of the total pixels) at each grayscale intensity of the diaphragm ultrasound image in controls (red curve) and patients (black and grey curves). Among healthy subjects, the 95th percentile for the average echodensity (grayscale value) of the whole control group was 65. Black curve represents patients with ED50 below the 50th percentile and grey curve the patients with ED50 above the 50th percentile (ED50 50th percentile = 40) The boxplots (right graphs) represent the distribution of ED50, ED85, and HEA65 (from the left to the right) in controls and patients. Boxplot corresponds to the median with the inter-quartile range (IQR); the lower and upper whiskers extend from the hinge to the lowest and highest (respectively) values that are within 1.5 × IQR of the hinge.