This is the 2D companion to the 3D blood-circulation simulator, built on the same closed-loop pump-and-pipes idea but driven by the actual cardiac-output equations instead of a fixed heart rate: the right heart sends deoxygenated blood to the lungs (pulmonary circuit) to pick up O₂ and dump CO₂, and the left heart sends the freshly oxygenated blood out to the body (systemic circuit), which returns it deoxygenated to start again.
Cardiac output: CO (L/min) = HR (bpm) × SV (mL) / 1000
Mean pressure: MAP (mmHg) = CVP + CO × TPR (CVP ≈ 3 mmHg central venous pressure)
Pulse pressure: PP (mmHg) = SV / Ca (Ca ≈ 1.75 mL/mmHg arterial compliance)
Systolic/diast.: SBP = MAP + (2/3)·PP, DBP = MAP − (1/3)·PP
Transit time: t (s) = (total blood volume 5 L / CO) × 60
- Heart rate — beats per minute; raising it directly raises cardiac output (and animation speed) and shortens the time for blood to complete one full circuit.
- Stroke volume — blood ejected per beat; also drives cardiac output, and independently widens or narrows the systolic/diastolic split (pulse pressure) via arterial compliance.
- Vascular resistance — total peripheral resistance (TPR) the vessels present to flow; for a fixed cardiac output, higher resistance means higher blood pressure — the same output has to push harder against tighter pipes.
- Dot colour flips from blue (deoxygenated) to red (oxygenated) exactly at the lung capillary bed, and back to blue at the tissue capillary bed, matching real gas exchange.
Real-world relevance: MAP = CO × TPR (plus venous pressure) is the core equation clinicians use to reason about blood pressure — a drop in cardiac output (e.g. heart failure) or a rise in resistance (e.g. vasoconstriction) both raise or lower pressure predictably, which is exactly why blood-pressure medications target one side or the other of this equation.