Why doesn't oxygen cause decompression sickness?

[Puppeteer]

One other note from a pure chemical basis, if you were to get bent on oxygen and had bubbles in your blood or tissues, those bubbles would probably not redissolve really quickly. Quicker than nitrogen bubbles for sure, as oxygen is being used by the body, but a bubble in the blood has much lower surface area than the exposure in the lungs.

If the blood remains saturated with oxygen, there is little driving force for the bubbles to redissolve, and even if the blood is deficient in oxygen (eg near tissues or in veins returning to the heart and lungs), redissolution would be limited by the diffusion rate away from the surface of the bubble. Redissolution can be enhanced in basically 3 ways. 1) Increase the pressure, so that the bubble is more concentrated than the blood plasma which increases the differential pressure between bubble and plasma, 2) decrease the amount of dissolved gas in the blood/plasma (probably not healthy in the case of oxygen) which again increases the relative concentrations between bubble and plasma or 3) Somehow increasing the surface area between the bubble and plasma/blood, which improves kinetics of exchange, which the lungs are really good at while keeping actual gas out of the blood.

Theoretically reducing the temperature of the blood would also drive redissolution of oxygen as oxygen is more soluble in water at lower temperatures, but again, not healthy.

Bubbles in the blood ain't good. Don't get bent on any gas. Keep that gas in the lungs where it belongs.

 

[jale]

Not exactly. More like a mechanical gas embolism. Fish have a swim bladder which is entirely internal, they have no way to "exhale" that gas it has to redissolve in their bloodstream and get expelled across their gills. The swim bladder is used to maintain their buoyancy and orientation.
Fish at (significant) depth that are rapidly brought to the surface faster than they can circulate and expel the rapidly expanding gas in their swim bladders generally die. The now enlarged swim bladder pushes most of their other organs every which way, their stomach often will be partly inverted through their mouth for instance. Unless returned to depth their chances of survival are very low. Even when recompressed they often die.

Hence Pyle's stops

 

[duke dive medicine]

One other note from a pure chemical basis, if you were to get bent on oxygen and had bubbles in your blood or tissues, those bubbles would probably not redissolve really quickly. Quicker than nitrogen bubbles for sure, as oxygen is being used by the body, but a bubble in the blood has much lower surface area than the exposure in the lungs.

If the blood remains saturated with oxygen, there is little driving force for the bubbles to redissolve, and even if the blood is deficient in oxygen (eg near tissues or in veins returning to the heart and lungs), redissolution would be limited by the diffusion rate away from the surface of the bubble. Redissolution can be enhanced in basically 3 ways. 1) Increase the pressure, so that the bubble is more concentrated than the blood plasma which increases the differential pressure between bubble and plasma, 2) decrease the amount of dissolved gas in the blood/plasma (probably not healthy in the case of oxygen) which again increases the relative concentrations between bubble and plasma or 3) Somehow increasing the surface area between the bubble and plasma/blood, which improves kinetics of exchange, which the lungs are really good at while keeping actual gas out of the blood.

Theoretically reducing the temperature of the blood would also drive redissolution of oxygen as oxygen is more soluble in water at lower temperatures, but again, not healthy.

Bubbles in the blood ain't good. Don't get bent on any gas. Keep that gas in the lungs where it belongs.

Some fine detail points to add to this. First, this is a strictly theoretical discussion. For all practical purposes, divers will not have O2 bubbles in their blood. However, should a diver manage to survive breathing O2 at a high enough partial pressure to potentially produce bubbles on decompression and then decompress in such a way as to evoke clinically significant oxygen bubbles, the partial pressure of oxygen in the blood will rapidly decrease after surfacing. An analogy would be our hyperbaric oxygen patients; we can produce arterial pO2s in excess of 2000 mmHg on 100% O2 at 60 feet (normal reading on room air at sea level is 85-100). The arterial pO2 returns to baseline within 15 minutes of surfacing the chamber. In our theoretical discussion, this would also be a significant driver of bubble resolution.

Best regards,
DDM