EXERCISE CONDITIONING REDUCES THE RISK OF NEUROLOGIC DECOMPRESSION ILLNESS IN SWINE

During development of a pig model of neurologic decompression illness (DCI) we noted that treadmill-trained pigs seemed less likely to devel op DCI than sedentary pigs. The phenomenon was formally investigated. Twenty-four immature, male, castrated, pure-bred Yorkshire swine were conditioned by treadmill running, while 34 control pigs remained seden tary. All pigs (weight 18.75-21.90 kg) were dived on air to 200 feet o f seawater (fsw) in a dry chamber. Bottom time was 24 min. Decompressi on rate was 60 fsw/min. Pigs that developed neurologic DCI were treate d by recompression, Pigs without neurologic signs were considered neur ologically normal if they ran on the treadmill without gait disturbanc e at 1 and 24 h postdive. Of the 24 exercise-conditioned pigs, only 10 (41.7%) developed neurologic DCI, compared to 25 of 34 (73.5%) sedent ary pigs (X(2) = 5.97; P = <0.015). Neither mean carcass density (adip osity) nor mean age were significantly different between groups. No pa tent foramen ovale was detected at necropsy. An additional control gro up of 24 pigs was dived to clarify the influence of weight. The result s suggest that the risk of neurologic DCI is reduced by physical condi tioning, and the effect is independent of differences in age, adiposit y, and weight.