Fig. 2

Ultrasound images comparing the PVS in a patient without pleural effusion and in a patient with pleural effusion during TPVB. (A) TPVB ultrasound image of a patient without pleural effusion. (B) TPVB ultrasound image of a patient with pleural effusion. The dashed line outlines the pleural effusion located between the visceral and parietal pleura. The area enclosed by solid lines represents the PVS, as identified by the anesthesiologist. TPVB (thoracic paravertebral block), PVS (paravertebral space), TP (transverse process), IIM (internal intercostal membrane), P (pleura), and VP (visceral pleura)