CPR involves repeated chest compressions about five centimetres (two inches) deep, but doesn’t always cause broken bones. About 30 per cent of patients undergoing CPR will end up with a fractured rib or, in four per cent of cases, a broken sternum. Some patients are more vulnerable than others – eg those with osteoporosis. The person performing the CPR also makes a difference: one study showed that laypeople are more likely to break ribs than doctors. In any case, fractured ribs are a small price to pay if the CPR saves a life.
Answered by Alex Cheung.