Laparoscopic surgery works inside a gas-filled cavity created by insufflating the peritoneal cavity with CO2. This 2D version plots the same control loop directly: a live pressure-volume (P-V) loop against the abdominal wall's compliance curve, and a scrolling strip chart of pressure and venous return over time — the two views a real insufflator log never shows side by side.
Elastance: P(V) = P_min + k · (V / V0)^n (wall gets stiffer as it stretches)
Gas balance: dV/dt = Q_in(t) − Q_leak(V) − Q_absorbed
Controller: Q_in = Q_set · clamp((P_target − P) / 2 + 0.05, 0, 1)
Venous ret.: VR(%) = 100 − c · max(0, P − 12 mmHg)^1.4 (IVC compression above ~12–15 mmHg)
- CO2 flow rate — the insufflator's maximum delivery rate; higher flow reaches target pressure faster and steepens the P-V loop's rising edge.
- Target pressure — the surgeon's set-point; the controller throttles flow as pressure approaches it, then trickles just enough to offset leak.
- Trocar leak — continuous gas loss around ports; the controller must keep pumping just to hold pressure once leak exceeds the trickle rate.
- Patient abdominal compliance — a floppier wall (higher compliance) needs far more volume for the same pressure; a stiff wall (low compliance) reaches dangerous pressure on very little gas — watch the P-V curve reshape as you drag it.
- Instrument exchange — briefly opens a port to ambient air, spiking the leak rate; the P-V loop dips and the controller has to re-climb the curve.
- Above roughly 12–15 mmHg, rising intra-abdominal pressure compresses the inferior vena cava and reduces venous return to the heart — the readout mirrors this real hemodynamic effect and turns amber, then red, exactly when the strip chart's two traces cross.
Real-world relevance: this pressure/flow control loop is exactly what runs inside every clinical laparoscopic insufflator (Storz, Olympus, Stryker), and IAP-driven venous return impairment is the reason anesthesiologists watch pressure trends during long laparoscopic and robotic-assisted cases.