Lack of teratogenic effects of air at high ambient pressure in rats

The purpose of the research was to determine if pregnant rats subjected to a maximum tolerated duration of exposure to air at 6 atmospheres absolute pressure (ATA) (50.3 meters seawater) would have an increased frequency fetal death, resorption, low birth-weight, or malformations. Ninety pregnant rats were assigned to one of three exposure schedules during organogenesis: days 9-11, 12-14, or 15-17, and were randomized between one treatment and two control groups. The treatment group was subjected to 6 ATA for 70 minutes with compression and decompression at 1.8 ATA (18.3 meters seawater)/minute. Control groups were exposed to either 1 ATA of air (surface) within the hyperbaric chamber, or 1 ATA of air outside the chamber. For 30 minutes following decompression, chamber-treated animals were placed in a slow, motor-driven rotating cage, and assessed for gait disturbances from decompression sickness. On Day 20 of gestation, laparotomy was performed, and corpora lutea, implantations, and resorptions were counted. Fetuses were weighed, sexed, and examined for gross malformations. Subsequently, they were fixed, sectioned, and examined for visceral anomalies. Minor visceral anomalies and anatomical variations were present in 16.3% of all fetuses; however, no significant differences existed between groups. Similarly there were no significant differences when number of resorptions, number of dead fetuses, mean fetal weights, and malformations were compared by analysis of variance. Finally, there was no relation between symptoms of decompression sickness and any of the above measures. These results indicate that exposing rats to air at increased atmospheric pressure does not affect fetal health or survival.