Pulmonary inflammation in reaction to diving - Exercise as a perconditioning method

Diving is an increasingly popular activity, and may cause decompression sickness (DCS). Bubbles form when surrounding pressure is exceeded by the sum of the tension of gases in the tissue and are strongly correlated to development of DCS. The direct mechanism causing DCS remains unknown. We hypothesized that bubble load would induce an inflammatory reaction in pulmonary tissue, since bubbles are filtered through the lungs, and that this would be attenuated by pre-dive exercise. Forty-nine female Sprague-Dawley rats were divided into 4 groups: control, diving, exercise and exercise + diving. The exercise consisted of 100 minutes of running downhill (-16°) on a treadmill, followed by a resting period of 48 h. Diving rats were compressed to 709 kPa for 50 minutes. All rats were observed for 4 hours, thereafter pulmonary tissue was collected. RT-PCR was used to analyse expression of IL-1β, IL-10 and TNF-α, whereas ELISA was used to measure levels of MPO. No significant difference in expression of IL-1β, IL-10 and TNF- or in levels of MPO was found between the groups. Level of bubble load in diving rats was not affected by pre-dive exercise. Neither in the group that had dived, nor in the group that had exercised and dived, inflammatory reaction correlated significantly to bubble burden. Our results implicate that bubbles per se does not induce an pulmonary inflammatory reaction, but are limited by a loss of integrity of the RNA samples as measured by RIN values.