Grading of sonographic features
| Grade | Value | Ultrasonic features |
| 0 | Pneumothorax | B mode: lung sliding absent, repetitive A lines present, lung point present, no fluid detectable and B lines absent M mode: seashore sign absent and stratosphere sign present |
| 1 | Pleural effusion | B mode: hypoechoic structure or echo-free space between both pleura, and gliding sign absent M mode: sinusoid sign if a small amount of liquid |
| 2 | Lung sliding | B mode: gliding sign and B lines present M mode: seashore sign present |
| 3 | Pleural symphysis | B mode: gliding sign questionable or absent, B lines absent, and pleural thickening with posterior enhancement M mode: seashore sign absent |