When the skin is burned and depending on the severity of the burn, tissue will die, this dead tissue is called an eschar which is inelastic and can’t expand.
When the burn is a circumferential (burned all the way around) second and third degree burn, eschar will form and with the edema (fluid leak from injured vessels) formed; the pressure will increase in the burned area. If this happens in arms and legs, this will lead to compression of the underlying veins arteries and nerves acting like a tourniquet. If the circumferential burn happens in the neck or chest, the pressure will prevent chest expansion leading to breathing problems. In these situations escharatomy is often needed.
Escharotomy is a surgical procedure done by making an incision through the eschar to relieve the underlying pressure, measuring the pressure in the compartment (closed space of nerves, muscle tissue and blood vessels) distal (furthest) to the affected area is one of the parameters used to determine the timing of escharatomy. Another way to determine the timing of the escharotomy is clinically by assessing the perfusion (the flow of blood) distal to the area affected.