A devastating 9.0-magnitude earthquake has rocked Japan killing thousands of people. Many more are missing. How long can the average person survive under rubble?
For a young, healthy person who started the ordeal well-hydrated and well-nourished, the chances of surviving are fair if they are rescued within about four days. The time period goes down considerably under different conditions.
Someone who is injured, particularly if they have lost blood, has a very poor chance of surviving for more than 24 hours. In fact, even if someone is not injured, experts agree that the person's chances of survival drop once 48 hours have passed.
No food or water
What happens to the body without food and water over an extended period?
The lack of food is of less importance than the lack of water. The body can call on fat stores and eventually the protein in muscle for fuel, but it cannot draw water from anything other than external sources.
Kidneys are the organs most severely affected by lack of water. Their chief function is to maintain both the volume and the concentration of body water.
Without water, the body gradually dehydrates because water intake no longer replaces water lost through sweating, breathing, passing urine and absorption in the gut.
With increasing dehydration, the blood becomes thicker, which causes the kidneys to retain water and concentrate the urine they do produce.
This causes the blood pressure to fall, resulting in less blood passing through the kidneys. Thus yet more water is retained and urine becomes even more concentrated. Eventually, no urine is produced at all.
Once this happens the person is in danger of kidney failure.
As dehydration increases, so does thirst, and tiredness. Eventually, when the kidneys have stopped producing urine, the person may become confused and even lapse into a coma as the kidneys start to fail.
Drop in blood pressure
Obviously, in a traumatic situation such as an earthquake many other factors might complicate this process. Shock results in decreased blood pressure, which speeds up the inevitable course of kidney failure.
Other injuries may cause blood loss on top of a lower blood pressure. Any chest injury can lead to breathing difficulties.
Not enough air
Some people die because they are trapped under rubble in a small space with limited quantities of air.
The human body is very vulnerable yet also amazingly resilient, and miracles do happen: Ismael Cimen, a Turkish four-year-old boy, was rescued after spending 140 hours under the rubble in the 1999 earthquake.
(Health24, updated 2011)