The discovery and understanding of barotrauma-related injuries began over 100 years ago, long before the invention of scuba diving. It was first described when laborers began to work inside caissons that were being used to build bridge supports. In order for a bridge to stand, the supporting pillars had to be set on bedrock and not the muddy bottom of a river. The caisson was invented to remedy this problem.
A caisson is a large, thick, wooden container not unlike a boat. Once built, it was floated to the proposed building site and then flipped over and sunk to the bottom. Air was then pumped into the caisson to force the water out which created pressure inside the structure. Laborers could then descend into the caisson and dig out the muck on the bottom of the river. As they removed the mud and muck, the caisson would slowly settle deeper and deeper into the river bed until it reached bedrock. As it went deeper, the pressure inside the caisson had to be increased to hold the water back. Increasing the pressure inside the caisson created problems for the laborers who were experiencing terrible muscle and joint pains at the end of the work day when they came out of the pressure-filled structures. Typically, they had to walk bent over, hence the name “the bends” for this decompression illness. When they returned to the pressure-filled caisson, the symptoms would resolve.