In a manikin study of CPR, there was a decrease in mean depth of chest compressions when the height of the bed was over 20cm above the knee height of the nurse doing the compressions.
The study has several limitations, but serves as a helpful reminder that adjusting the height of the bed to suit the rescuer is an option not to be forgotten. At least for those areas where manual CPR is still performed.
Effects of bed height on the performance of chest compressions
Emerg Med J. 2009 Nov;26(11):807-10