Thoracentesis is typically performed between
①the 6th and 8th ribs along the midclavicular line,
②☆the 8th and 10th ribs along the midaxillary line (above image),
③and the 10th and 12th ribs along the paravertebral line.
This allows pleural fluid to be drained without risking lung injury (which can occur at higher insertion sites). However, insertion of a needle ☆below the 9th rib still risks penetrating abdominal structures.