Patent foramen ovale
Patent foramen ovale or
PFO is a pathological condition of the
heart in which an embryonic hole between the right and left
atrium fails to close by the time of birth. There are two types:
- Ostium primum defect
- Ostium secundum defect
PFO can cause
decompression sickness in divers because a proportion of
venous blood carrying inert gases, such as
helium or
nitrogen does not pass through the lungs. The only way to release the excess inert gases from the body is to pass the blood carrying the inert gases through the
lungs to be exhaled. If that inert gas-laden blood passes through the PFO, it avoids the lungs and the inert gas is more likely to form large bubbles in the
arterial blood stream causing
decompression sickness.