Usually, the blood pressure on the arterial left side is higher than the venous right, which prevents right to left flow. This is known as a paradoxical embolism and is depicted in Figure 1. The lungs are an effective filter, and a right to left shunt, such as a patent foramen ovale (PFO), is therefore a route for bubbles to avoid this filter and enter the arterial system. These symptoms are frequently neurological in nature and can be profound. Symptoms usually appear shortly after, or within 30 min of surfacing, but can have delayed onset. AGE is caused by arterial bubbles as a result of ruptured lung alveoli from gas trapping in the lungs or blood shunting from the venous right atrial side to the arterial left atrial side of the heart.

DCS occurs as a result of venous bubbles forming in the tissues and vessels, which can cause mechanical, embolic and biochemical effects with manifestations ranging from trivial to fatal. The differentiation of the pathological processes in practice can be difficult, but the treatment is similar hence, both are given the modern overarching term of decompression illness. We hope this guideline and flow chart helps address these issues with regard to PFOs and diving.ĭecompression illness (DCI) encompasses decompression sickness (DCS) and arterial gas embolism (AGE). Ideally, we should advise and apply guidelines that are consistent and based on best available evidence. Why this is the case is not clear, but the divers look to doctors for guidance on PFO screening and closure both of which are not without risks. Venous bubbles after diving and right to left shunts are common, but DCI is rare. We present the basic physiology and current existing guidelines for doctors, advice on the management and identify which groups of divers should be referred for consideration of PFO screening.

There is an agreement that PFO screening should not be done routinely on all divers however, when to screen selected divers is not clear. There is therefore some underlying knowledge and understandable concern in the diving community about the presence of a patent foramen ovale (PFO) as a cause of decompression illness (DCI). Divers are taught some basic physiology during their training.

Bsac dive tables pdf