Effects of vagotomy and increased blood pressure on the incidence of decompression-induced pulmonary hemorrhage

Sixty eight male rats were divided into four groups. They were rapidly decompressed from one atmospheric pressure (760 mmHg) to an ambient pressure of 30 mmHg in 0.4 s. It was found that about half of the control animals (47%) revealed mild pulmonary hemorrhage, while all of the cervical vagotomized rats (100%) showed mild to severe pulmonary hemorrhage. Besides, 16 of 17 epinephrine injected rats (94%) and 15 of 17 carotid arteries occluded rats (88%) also exhibited decompression-induced pulmonary hemorrhage. The differences between control and experimental groups were statistically significant. The results suggest that during rapid decompression, the overexpansion of the alveoli accompanied by an increased pressure in the pulmonary vessels may be responsible for the production of pulmonary hemorrhage.