This site spends pages and pages talking about nerve damage... and this is the lone little page on reduced circulation. That's because nerve damage is more of a safety issue for most bondage. However, reduced circulation can have risks and does not tend to increase sexy bondage fun times (and can complicate detection of nerve damage), so it’s better to avoid it.There is a tendency to conflate decreased circulation and nerve damage, or to think that decreased circulation causes nerve damage, which is not directly the case.Let's first define what we mean by "reduced circulation," as there are two major subtypes:
Impaired venous return: This is by far the most common circulation issue you will see in bondage. This refers to situations where blood flow leaving the limb in the veins is obstructed (or partially obstructed), but blood flow into the limb via the arteries is unaffected. Because arteries are deeper and have tougher walls than veins, veins are almost always affected first. Signs that venous return is compromised includes the limb changing color and becoming purple- or red-ish, as well as generalized numbness. Over the long run (hours, not minutes), blocked venous return can be dangerous, but it is incredibly common in bondage and not an emergency situation (although it can complicate detection of nerve damage). Often this can be addressed by "re-dressing" wraps to slightly change their position.
Impaired arterial flow: This is quite uncommon in bondage as it is rather difficult to achieve. This refers to a situation where you have blocked off arterial flow into a limb. Signs of this include the limb turning white and diffuse numbness in the limb. This is obviously much more urgent than impaired venous return and should be addressed by releasing the effected limb from bondage.
The next question, of course, is how do you avoid causing reduced circulation?
Select an appropriate bondage material. Very stretchy materials (bungee cords, tights, rubber bands, surgical tubing, etc) have a lot of potential to act as a "tourniquet" around a limb, because by the time they are tight enough that the restrained person can't just wiggle out, they are very tight indeed and are likely keeping blood from getting out (or in!) as well. There are ways to use stretchy material in bondage, but it's important to be aware of the potential for problems. Many people prefer to use something that has some softness and minimal stretch—scarves can work well, or of course rope (hemp/nylon/etc)!
The amount of the bondage material that will be against the skin is key (with rope, this translates as the thickness + number of wrapping turns), especially if the bondage will be load bearing or the restrained person will be struggling. Even small increases in the amount of contact against the skin can make bondage significantly more comfortable (and safer)—consider that a 100 lb person in high heels exerts 15 times more pounds per square inch than a 6,000 lb elephant. Generally an inch of coverage (for 1/4 inch diameter rope, about 4 strands, which means going around twice with doubled-up rope) is a good place to start for something like basic limb bondage. Larger bodied folks often need more wrapping turns to be comfortable, although when you get beyond 6 strands you reach the point of diminished returns, and maintaining consistent tension becomes more difficult.
Rope placement is also important. If possible, stick to areas with more padding—avoid placing rope around joints (elbows, knees, arpits, groin) where blood vessels are close to the surface with little padding.
Many bondage experts recommend a “two finger rule” (being able to slide at least two fingers under the rope) for bondage tightness.
Keep in mind that bondage will shift as the scene progresses, especially if the restrained person is struggling/squirming.
Signs of decreased circulation include cold, color change, and numbness. These signs and symptoms generally occur SLOWLY. Some color and temperature change in a bound limb is to be expected and is certainly not a bondage emergency. Establish a baseline by assessing the limbs before you start, so that you can tell if there are changes. You can also check capillary refill—if it is prolonged, you know circulation is decreased. Again, this is not a bondage emergency, but might prompt you to adjust your bondage and certainly should prompt you to monitor and communicate with your partner. Mild color/temperature change is quite a different thing from a limb that is white, cold, and has no pulse—use common sense here. Every person is different.There are a few areas of the body where circulation does really matter. The head, for one—rope around the neck is high risk for oh so many reasons. The cock and balls are another area where circulation matters—if they're turning colors or having temperature changes, it's past time to take the bondage off.
Next: After a Rope Scene