Highest incidence of pneumothorax occurs when branchial plexus is blocked by which route

The incidence of pneumothorax may be as high as to 6% when brachial plexus is blocked through supraclavicular route but founately most of these pneumothorax resolve by themselves without treatment. Supraclavicular brachial plexus block: cellulitis/abscess over the site of injection. Use caution in patients with poor pulmonary reserve, as a resultant pneumothorax may significantly worsen their respiratory status (example: known pneumonia on the contralateral side ref Robbins 9/e pg 456