Cpr device with manual activation of active decompression and force measurement of active decompression

A mechanical cardiopulmonary resuscitation (“CPR”) device comprising:

• a piston comprising:
• a piston rod,
• a piston sleeve concentric to the piston rod and configured to slide relative to the piston rod in a first direction, and
• a spring configured to resist movement of the piston sleeve in the first direction, the spring having a first spring rate from a pretensioned position to a first deflection distance, the spring having a second spring rate from the first deflection distance to a second deflection distance, the second deflection distance being greater than the first deflection distance, the second spring rate being greater than the first spring rate;
• and
• a driver coupled to the piston and configured to extend the piston toward a chest of a patient and retract the piston away from the chest of the patient.

A mechanical cardiopulmonary resuscitation (“CPR”) device comprising:

• a piston comprising:
• a piston rod,
• a piston sleeve concentric to the piston rod and configured to slide relative to the piston rod in a first direction, and
• a spring device configured to resist movement of the piston sleeve in the first direction, the spring device having a first spring rate from a zero deflection distance to a first deflection distance, the spring device having a second spring rate from the first deflection distance to a second deflection distance, the second deflection distance being greater than the first deflection distance, the second spring rate being greater than the first spring rate;
• and
• a driver coupled to the piston and configured to extend the piston toward a chest of a patient and retract the piston away from the chest of the patient.