Dry suits and skin Bends

About an hour after I completed a single drysuit dive on air, I noticed odd bruise-like lines on both shoulders and behind both knees, but no other  symptoms. The uneventful dive was to 65 feet for 24 minutes in a lake with a water temperate of 50°F. The drysuit was tight, however, around the shoulders, armpits and knees. How would I know if this is skin bends or suit squeeze?

When differentiating between drysuit squeeze and the many causes of diving-related skin conditions, we can quickly eliminate most types of marine life injuries simply because the skin is completely covered by the suit. Cutaneous decompression sickness (DCS), or skin bends, is a mild form of DCS. Drysuit squeeze is a type of barotrauma or pressure injury to the skin that is caused by a failure to add air to your drysuit during descent.

While descending, the volume of the air spaces is reduced and trapped in the folds of the suit. The skin tends to be sucked into these folds. Divers will often recall the suit being tight or ill-fitting. The diver may find linear marks or bruises, usually beneath the drysuit's valves and seams. This condition is usually painless and clears within a few days. To avoid suit squeeze, divers should add just enough gas to the suit during descent and make sure to vent excess gas when ascending.

Cutaneous DCS typically presents as a blotchy, bruise-like rash generally appearing in areas of the body with the most adipose tissue (body fat), such as the abdomen, thighs, buttocks and breasts. The condition usually responds well to surface-level oxygen therapy. DAN has observed, however, that at least 20 percent of divers with suspected skin bends may also experience visual disturbances, weakness, confusion or other neurological symptoms that require recompression treatments. It is important that divers do not overlook these symptoms. DAN always recommends a thorough medical evaluation and appropriate treatment of divers with suspected skin bends.
— Travis Ward, EMT-P