That pressure can make it difficult to breathe even when the victim's airway is unobstructed; it increases with every inhalation, making it more critical to secure breathing space for a victim in that situation. It has been likened to concrete, cement or quicksand; and described as making it impossible to even wiggle toes inside a shoe or boot; one survivor said he felt as if an " semi truck had parked on [his] chest." The compression also makes it hard for blood to circulate, reducing the oxygen that gets to cells and increasing the amount of toxins in the system.
