Fig 1 Perfusion index values at different time intervals in patients with successful and failed blocks. A reference line at PI 3.3 is provided. Horizontal lines are medians, boxes are quartiles, and whiskers are ranges. PI, perfusion index. From: Predicting successful supraclavicular brachial plexus block using pulse oximeter perfusion index Br J Anaesth. 2017;119(2):276-280. doi:10.1093/bja/aex166 Br J Anaesth | © The Author 2017. Published by Oxford University Press on behalf of the British Journal of Anaesthesia. All rights reserved. For Permissions, please email: journals.permissions@oup.com