Intrapulmonary Shunts: Another Cause for a Right-Left Shunt
Many of us are familiar with the concept of PFO’s and how they may be responsible for allowing bubbles to cross from the venous (pulmonary) to the arterial side. When this occurs, we are talking about a Right-Left Shunt, RLS and a potentially increased risk for developing Type II DCS. There are other sources that may lead to a RLS, such as intrapulmonary shunts, IPSs.
This article reports on the existence of intrapulmonary anastomoses or IPAs (which are cross-connections between adjacent blood vessels) that may open and close at various circumstances causing a shunt. It appears that some people are more prone to developing an open IPA than others – thus increasing their risk without having a PFO. It also suggests strategies of prevention.
According to this article, an IPA can open during mild to moderate exercise. Swimming at the surface, climbing up a dive ladder, manipulating heavy gear are all examples of how these IPAs could open, allowing potential bubbles to cross-over to the arterial side.
The incidence of arterialization after diving was reported to be 13% at rest to 52%. Interestingly, breathing oxygen appears to close them again. In divers observed to arterialize, oxygen was administered and arterialization seized around 55 seconds. If switched back to room air, arterialization resumed.
This article supports the notion of “taking it easy” after a dive and provides an scientific explanation for healthy post-dive behavior. Perhaps staying on the loop breathing increased PO2s while climbing up the ladder and a few minutes thereafter while resting is not such a bad idea, either.