CPR Chest Compression Biomechanics Simulator

Compression Mode

Rescuer & Patient Parameters

Target depth 5.5 cm

Compression rate 110 /min

Patient chest wall

Live Readouts

Press Start or hold to compress

Compression depth

0.0 cm

Achieved rate

— /min

Full recoil

— %

Push force

0.0 N

How it works

The sternum is modelled as a point mass on a nonlinear spring-damper — the same rigid-body-plus-force-feedback approach used in real mannequin trainers. Newton's second law drives the motion every frame:

m·a = F_hand(t) − k(x)·x − c·v
k(x) = k0 + k1·x²   (rib cage stiffens as it compresses)
x = compression depth (m), v = ẋ, a = ẍ

In Auto mode the push amplitude is not fixed — a proportional feedback controller (the same PID family named in the source article) adjusts it every cycle:

F_amp ← F_amp + Kp·(x_target − x_peak,last)

so the simulated rescuer converges on the requested target depth regardless of the chosen chest stiffness, exactly like a real force-feedback trainer correcting a learner's technique in a closed loop.

Auto Compressions — drives repeated half-sine pushes at the chosen rate; the controller above tunes their strength to hit the target depth.
Hold to Compress — apply your own downward force directly (mouse/touch/space); release to watch the spring recoil the sternum, exactly as an unclamped elastic system does.
Full recoil reads how close the sternum returns to 0 cm between compressions — leaning on the chest (incomplete recoil) is a real, guideline-flagged CPR error.
AHA/ERC guidelines target 5–6 cm depth at 100–120 compressions/min with full recoil between pushes — the guideline box turns green when both are met.

Click/hold the chest to compress manually

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