Cinephotomicrography of dog spinal vessels during cord-damaging decompression sickness

Thirty-three dogs were anesthetized, laminectomized in the lower thoracic, upper lumbar region, and exposed to simulated 220 ft air dives of 5 to 60 minutes. Cinephotomicrography of the epidural vertebral venous system and dorsal pial vessels was done predive and postdive. The epidural vertebral venous system became blocked by bubbles in 24 animals. Eighteen animals evaluated for clinical and/or pathologic signs of cord damage all manifested positive signs. In 10 dives made by eight dogs, epidural vertebral venous system obstruction did not occur, and signs of cord damage were absent after nine of these dives. After one dive, a dog manifested cervical cord damage remote to the region of epidural vertebral venous system under observation. Acute pulmonary hypertension and central venous congestion were not essential prerequisites for epidural vertebral venous system occlusion to occur. These experiments permit further analysis of the pathogenesis of spinal cord damage in decompression sickness.