They're pretty simple once you break the functions down. Some multiplace chambers run directly from a compressor/volume tank, and some (like the ones at Duke) are supplied from HP flasks that are charged as needed. There's typically a primary air supply and exhaust valve for each lock, and also a secondary air supply for each. Oxygen for the BIBS (built-in breathing system) masks or oxygen head tents is supplied through separate plumbing. The one in the photo that
@JamesBon92007 looks like a twin-lock deck decompression chamber like you'd find on a commercial diving station. Locks are really chambers within the chamber. If you looked in the hatch at the end you'd see another hatch about 1/4-1/3 of the way back; that's the inner lock hatch. Chambers like that are typically operated with the inner lock at pressure and the outer lock on the surface so that supplies and personnel can be locked in if necessary. Many chambers have a medical lock (basically a small air lock) for sending in supplies.
The chamber simulates the pressure of diving. The function of diving gear is to deliver gas at a pressure that allows the diver to inflate his or her lungs against the ambient water pressure, so the pressure of the gas the diver is breathing is essentially the same as the ambient water pressure. A person in a chamber that's pressurized to a depth equivalent of 60 feet of sea water (2.82 atmospheres of pressure, or 26.7 psi gauge) is breathing gas at the same pressure that a diver at 60 feet would be breathing.
Chamber treatment for DCS does a couple of things. First, the increased pressure in the chamber will cause any remaining bubbles in the diver's body to shrink, which will improve circulation to the affected area. The diver breathes oxygen for most of the treatment, which dissolves oxygen into the plasma by the same principle that causes inert gas to dissolve in the body: Henry's Law. Oxygen that's dissolved in the plasma is carried to tissues when the plasma leaks out of the capillaries (this is physiologically normal, it's what your lymphatic system is for). Since there's so much more oxygen in the plasma, it penetrates deeper into the tissues.
Hyperbaric oxygen has other physiologic effects: the reactive oxygen species ("free radicals") produced in hyperbaric hyperoxia will basically scavenge nitric oxide, which is an endogenous vasodilator - this produces net vasoconstriction, which can help with inflammation. It also interrupts the inflammatory cascade by interfering with beta-2 integrin, which is a protein that helps white blood cells bind to the walls of the blood vessels in areas of inflammation. In people with chronically poor circulation (diabetes, radiation tissue damage), the burst of oxygen activates the body's own system for growing new capillaries.
Hope this helps!
Best regards,
DDM