Decompression after diving often causes gas bubbles to occur in the systemic veins. Presumably, bubbles occur in tissues rich with fat, and one of the fattiest areas of the body is the mesentery, which holds together gastro-intestinal tract. Venous blood drains from this area into the portal vein of the liver, which directs it through capillary beds to process the nutrients it carries. If any gas bubbles occur in the mesentery, they would likewise be carried by venous blood into the portal vein.
Generally, the liver is not considered a target for decompression sickness (DCS), but there have been a few cases in which gas was accidentally found in the livers of divers. It was not, however, clear whether the gas preceded or appeared after decompression.
Studies describing gas in the portal veins of animals has enabled researchers to develop a model that predictably reproduces portal vein embolization. The decompression stress in the model is severe enough to cause many bubbles all over the body, including the portal vein and liver tissue. Damaged capillary endothelium and liver cells release various markers and start an inflammatory cascade that can be measured. It is suspected that nitric oxide (NO) plays a major role in these processes and that the severity of DCS-caused injuries could be mitigated by controlling the NO.1
In a recent study, Peng and co-authors2 used this model to study mechanisms and possible prevention for decompression injury of the liver. They administered generic rosiglitazone to animals, which is supposed to reduce inflammatory effects mediated by NO. Indeed, the animals receiving this drug developed fewer symptoms of DCS, produced fewer markers of endothelial and liver injury, and had less inflammation. Researchers assigned most of the beneficial effects of rosiglitazone to protective effects on endothelium.
This study is a reminder that DCS is a systemic disease. Endothelium protection may be a good strategy to mitigate the risk of DCS; however, the drug used in this study to protect animal livers from decompression injury may not necessarily be helpful in human subjects. Because rosiglitazone is an anti-diabetic drug that lowers blood sugar, healthy people should not use it. It can also cause a number of serious and adverse health effects in people with certain health conditions. We still do not have drugs that can be safely used to prevent DCS, but that may soon change, if the rate of current research is any indication at all.
References
- L’Abbate A, Kusmic C, Matteucci M, Pelosi G, Navari A, Pagliazzo A, Longobardi P, Bedini R. Gas embolization of the liver in a rat model of rapid decompression. Am J Physiol Regul Integr Comp Physiol 299: R673–R682, 2010.
- Peng B, Chen MM, Jiang ZL, Li X, Wang GH, Xu LH. Preventive effect of rosiglitazone on liver injury in mouse model of decompression sickness. Diving and Hyperbaric Medicine 2017;47(1):17-23.