Background and Objectives: Several case reports have suggested that block of the brachial plexus by the vertical infraclavicular approach influences hemidiaphragmatic movement and ventilatory function. These effects have not been evaluated in a prospective study.

Methods: Thirty-five consecutive patients scheduled for elective surgery under brachial plexus anesthesia were included. A vertical infraclavicular block was performed with ropivacaine 0.75%, 0.5 mL/kg. Ipsilateral hemidiaphragmatic movement was measured by ultrasonography at maximal forced inspiration and sniff. Forced vital capacity (FVC) and forced expiratory volume (FEV₁) were measured by a portable vitalograph. All measurements were performed before the block procedure and at 5, 10, 30, and 60 minutes after the block.

Results: The block was successful in 34 of 35 patients. In 9 patients (26%), a change in hemidiaphragmatic movement (reduced or paradoxical) was observed. A significant decrease in ventilatory function was found in 8 of these 9 patients between baseline and at 60 minutes: FVC = −0.8 ± 0.4 L and FEV₁ = −0.7 ± 0.3 L, mean ± SD (relative decrease: FVC = 30 ± 14% and FEV₁ = 32 ± 13%, mean ± SD). Horner's syndrome was seen in 4 patients (12%), and in all, a change in hemidiaphragmatic movement was observed. No clinical signs of ventilatory dysfunction were noticed.

Conclusion: The vertical infraclavicular block can result in a change in ipsilateral hemidiaphragmatic movement, with a decrease of ventilatory function. Although a correlation between the presence of Horner's syndrome and hemidiaphragmatic dysfunction was observed, hemidiaphragmatic dysfunction also occurred independently.