Ultrasound devices make it possible to detect subclinical bubbles, the most common Doppler ultrasonic bubble detector. The use of this devices make possible to developed the concept of silent bubbles.

It was demonstrated that decompression free of signs and symptoms   in both human and animals could actually produce a gas phase. This clearly shows that there was little physical reality to a “critical supersaturation limit”. Now in the algorithm the degree of supersaturation governs the degree and rate in which a gas phase will grow, rather than whether it exist.

Bubbles form in the muscle capillaries and fat. As gas phase grows in the capillaries following decompression its enlarge to a point where the tiny gas is releases  into the venous return a flow with the blood, where is detected by a Doppler device. << This concept is very important for develop a good ascent velocity and deep stops decompression strategy! >> 

The growth phase results mostly in limb pain, probably the tendons and ligaments around the joints and not located it in the capillaries.

Physiologist monitor downstream bubbles in the blood flow, and try to simulate what’s occurring upstream. Understand that gas phase evolves from tissues not directly connect to the limb, muscle-fat, so the quantity of bubbles in the venous return don’t correspond with the magnitude of pain producing gas phase in the tendons and ligaments; << there’s a differences between quantity and sizes>>.

From previous knowledge you should remember that bubbles released into the venous system are filtered out by the lungs, the gas bubbles dissolve, and the gas diffuse into the alveoli and then exhaled. Only in rare cases where a large number of bubbles are present into the venous return, such as a missed decompression, the lungs will not be able to filter them; rather than dissolving it, bubbles pass through the pulmonary capillaries into the arterial side of the circulation where they block blood flow in other organs. The severity in this cases is the spinal cord, brain or heart are compromise.

I suggest you review PFO concept on the DSC lesson.