Pulse Lab by Myocognia

The complete guide to Pulse Lab

Everything Pulse Lab can do, and how to use it: every view, button, control, scenario, challenge and tool.

What Pulse Lab is

Pulse Lab is a free, interactive cardiovascular simulator that runs in your web browser. A real-time physiology model calculates the heart and circulation 10,000 times per second. You can change the heart, vessels, valves, lungs, drugs and support devices, and watch every beat respond.

• Free, no account, no download. Works on laptops, tablets and phones, and keeps working offline.
• Built for medical students, residents, fellows, nurses, perfusionists and educators.
• Every number is measured beat by beat from the simulated waveforms, not looked up in a table.

Educational use only. Pulse Lab is a teaching model. It is not a medical device and must never be used to make decisions about real patients.

Quick start (2 minutes)

1. Open Pulse Lab. You start on the Heart view with a healthy adult, and the heart beats in real time.
2. Press 📌 Snapshot (or S) to freeze this normal heart as a reference.
3. Open the Heart tab (left panel) and drag LV contractility (Ees) down to about 1.0. The left ventricle weakens and dilates, and pressure falls.
4. Press ⏩ Steady (or F) to jump to the new steady state. Every number on the right now shows its change (Δ) against your snapshot. The 💡 What changed, and why panel explains it in plain language.
5. Switch to Loops to see your new pressure–volume loop next to the normal one. Then try a Case challenge or Predict & Test (right panel).

The screen

Top bar

Panels

• Left: the Scenario picker and the control tabs.
• Centre: the views (pick one in the bar above the plots). Every plot has a ⤓ button to download it as an image. ⤢ Fit rescales the axes. Ea line adds the arterial-elastance line to the LV loop.
• Right: alarms, challenges, Predict & Test, the 💡 explanation panel, and all outputs in collapsible groups.

The 8 views

1 · Heart new

An animated four-chamber heart, and every movement comes from the simulation:

• Chamber size follows the real volume, so you see the ventricles fill and empty.
• Walls thicken as a chamber empties (wall mass is conserved) and glow with electrical activation. The atria flicker in atrial fibrillation.
• Valves open and close with the real flow. A leak shows as a yellow-to-teal jet, like colour Doppler.
• A conduction wave runs from the SA node across the atria, then from the AV node down the septum. In complete heart block you can see them come apart.
• Blood colour = oxygen saturation (purple venous, red arterial). Moving marks in the vessels follow flow.
• A pericardial effusion appears as a fluid layer. Devices appear in place: axial pump across the aortic valve, LVAD at the apex, ECMO cannulas, and the balloon pump inflating in the descending aorta.
• The label shows SYSTOLE / DIASTOLE, rhythm, heart rate and EF.

2 · Loops

Pressure–volume loops of the left and right ventricles, with the end-systolic line (ESPVR, its slope = contractility, Ees) and the end-diastolic curve (EDPVR, stiffness). The current beat is solid and the previous beat faded. Snapshots overlay in colour. Tick Ea line to draw arterial elastance and read Ea/Ees coupling.

Reading a loop: bottom edge = filling · right edge = isovolumic contraction · top = ejection · left edge = isovolumic relaxation. Width = stroke volume.

3 · Waveforms

Left heart pressures (LV, aorta, LA), right heart pressures (RV, PA, RA), and flows (aortic and mitral valve, pump/LVAD, ECMO) over the last 5 seconds.

4 · Monitor

A bedside monitor: ECG, arterial line, PA catheter, CVP and (when breathing) pleural pressure, with large numbers. The footer shows SpO₂, SvO₂, cardiac output and index, LA pressure and lactate.

5 · Echo

Spectral Doppler built from the simulated valve flows. Mitral inflow (E and A waves, E/A, deceleration time, diastolic pattern: normal, grade I–III, fusion, no A wave) and aortic outflow (Vmax, VTI, mean gradient, LVOT VTI). Regurgitant jets appear in the opposite direction.

6 · Circulation

A live map of the whole circulation (lungs, heart, body). Chamber size follows volume, colour follows oxygen saturation, and moving dashes follow flow. Devices and shunts are drawn in. It is paired with the hemodynamic profile: cardiac index against wedge pressure, with the warm/cold and wet/dry quadrants and a trail showing where the patient has been.

7 · Trends

The last 10 minutes of pressure (MAP, LAP, RAP), flow (total and native) and lactate/SvO₂. Every intervention you make is marked with a dashed line and label, so you see cause and effect over time.

8 · All

Everything on one page. Best on a large screen or projector.

Numbers & alarms

The right panel groups every measurement. Hover a name for its definition. Red = dangerous, amber = abnormal. With a snapshot visible, each value shows Δ vs the snapshot.

Alarms include hypotension, no effective circulation, low cardiac index, high left or right atrial pressure, myocardial ischemia, lactate, low SvO₂, low or differential saturation, tamponade physiology, pulsus paradoxus, pump/LVAD/ECMO suction, ECMO or LVAD backflow, a stopped pump, and the aortic valve not opening on ECMO.

The 7 control tabs

Drag a slider or type an exact value and press Enter. A • marks a value that differs from a normal adult. ↺ resets it.

Heart

• Heart rate; LV and RV contractility (Ees); LV V0 (shifts the end-systolic line, e.g. a dilated heart); LV and RV diastolic stiffness and scale; LV relaxation time τ; LA and RA contractility (the atrial kick).
• Coronary circulation: coronary flow limitation (%), Ischemia feedback (if O₂ supply stays below demand, contractility slowly falls) and 🩺 Revascularize (PCI).
• Rhythm: Sinus, AF or complete heart block; AV delay; escape rate.
• Baroreflex: when on, the body defends blood pressure (rate, vessel tone, contractility, venous tone) over about 10 s.

Vessels

Systemic vascular resistance (SVR), pulmonary vascular resistance (PVR), arterial and PA compliance, venous unstressed volume (venous tone) and venous compliance.

Valves

For each valve (aortic, mitral, tricuspid, pulmonary): the opening area (smaller = stenosis) and the regurgitant orifice (bigger = leak). Values act immediately, with no hidden switches. Also ASD and VSD size, pericardial effusion, pericardial stiffness (constriction) and Drain effusion (pericardiocentesis).

Lungs

Breathing: Off (steady loops), Spontaneous, or Ventilator. Also respiratory rate, pleural pressure swing (breath size or effort), PEEP and native lung SaO₂. A live box shows PPV, SVV and pulsus paradoxus.

Devices

• Catheter axial pump (LV → aorta): size small/medium/large, level P0–P9. Suction alarm if the LV empties. At P0 it leaks backward.
• Durable LVAD (LV apex → aorta): speed 3,000–9,000 rpm. Narrows the pulse. Suction if too fast and dry, backflow if too slow.
• ECMO: VA (supports the circulation, raises LV afterload) or VV (oxygen only), with pump speed in rpm. Includes Atrial septostomy to vent the left atrium.
• Intra-aortic balloon pump: ratio 1:1, 1:2 or 1:3 and balloon volume. Timing follows the rhythm automatically.

Drugs (12)

Dobutamine, milrinone, norepinephrine, epinephrine, vasopressin, dopamine, isoproterenol, phenylephrine, nitroprusside, nitroglycerin, nicardipine, esmolol. Each acts on contractility, heart rate, resistance, venous tone and relaxation through realistic, saturating dose–response curves. They combine, with caps at physiological limits. Stop all infusions clears them.

Bedside

Give fluid or remove blood (±250, 500, 1,000 mL over 10 s), bedside maneuvers (see below), haemoglobin, whole-body VO₂ and body surface area.

29 patient scenarios

Pick one from the Scenario menu (top left). Each loads at steady state, with a one-line explanation.

Bedside maneuvers (Bedside tab)

• 🫀 IVC occlusion: briefly blocks venous return for about 7 s. The LV loops walk down and to the left, and Pulse Lab fits the end-systolic line through the loop corners (Ees, V0, r²), exactly like a cath-lab measurement. The family of loops stays on the Loops view until you clear it.
• Passive leg raise: moves about 300 mL of venous blood toward the heart. A rise in output of 10% or more means fluid responsive. The result updates live.
• 💧 Fluid challenge 250 mL: gives 250 mL and reports the change in output after 40 s.
• 😤 Valsalva (15 s): strains, then releases. With the baroreflex on you see all four phases: rise, fall with reflex tachycardia, dip, then overshoot with reflex slowing.

Snapshots & the "What changed, and why" panel

Press 📌 Snapshot (up to 6, coloured A–F). Snapshots overlay on the loops and appear on the hemodynamic profile. Click a snapshot's letter to hide or show it, and × to delete it. Every output then shows Δ against the first visible snapshot.

The 💡 panel lists what you changed, why it matters (the physiology behind each change), the biggest effects, and what is happening right now, such as "Ea/Ees is 3.2: the ventricle and arteries are uncoupled" or "PPV 23%: likely fluid responsive".

9 case challenges

Right panel → pick a challenge → Start challenge. Reach all the goals and hold them for 8–15 simulated seconds. Your best time and number of interventions are saved on your device.

Predict & Test (19 questions)

Right panel → Start Predict & Test. Each question loads a patient and describes one change (for example "Start VA-ECMO" or "Open a severe mitral leak"). Predict whether each number will rise ▲, fall ▼ or stay about the same ↔, then press Run it. The simulator makes the change, grades your predictions, explains the physiology, and keeps a Before snapshot so you can compare the loops. Your running score is saved.

The Lab (🧪)

Experiments on a copy of the current patient. Your live simulation is never disturbed.

Parameter sweep

Vary any input (or blood volume) across a range, and plot up to 4 steady-state outputs against it, or against another output. Presets: Frank–Starling curve (output vs wedge as volume rises), afterload, heart rate, contractility, axial pump speed. Download the results as CSV or the chart as PNG.

Sensitivity

Choose an output (for example MAP or cardiac output). Pulse Lab moves 14 key inputs up and down by 5, 10 or 20% and ranks which ones matter most in a tornado chart.

Digital twin

Type in measured numbers from a case: heart rate, BP, CVP, PA systolic/diastolic, wedge, cardiac output, and optionally EF and EDV. Pulse Lab adjusts contractility, resistances, compliances, stiffness, the RV and blood volume using a Levenberg–Marquardt optimiser until the model matches, and shows a target-vs-model table with errors. Load twin into the simulator to test treatments on that copy. Use the built-in examples to try it.

Share, save, export, print

• 🔗 Share: a link that reproduces the exact patient (settings, volumes, lactate). No account needed.
• Deep links: add #scenario=cs, #challenge=c1, #predict=5 or #view=heart to the address, or combine them: #scenario=tamp&view=monitor.
• ☰ More → Save / load: keep up to 30 states in this browser, or export and import them as files.
• CSV exports: waveforms (pressures, volumes, flows, velocities), beat-by-beat data (40+ measures), and trends with your event log.
• 🖨 Printable report: plots, key values, settings, interpretation and timeline on one page.
• ⛶ Focus on plots: hides the side panels for teaching or projecting. ◐ Theme: light or dark.

Keyboard shortcuts

Space pause/run · S snapshot · F steady state · L Lab · 1 Heart · 2 Loops · 3 Waveforms · 4 Monitor · 5 Echo · 6 Circulation · 7 Trends · 8 All

Phones, install & offline

Pulse Lab adapts to phones and tablets. After your first visit it works offline. To install it like an app: Chrome/Edge → menu → Install app; iPhone/iPad → Share → Add to Home Screen.

Teaching with Pulse Lab

1. Project the Heart view, snapshot the normal heart, and ask the room to predict what one change will do. Then make it, and press Steady.
2. Send students a share link or deep link (for example #challenge=c2) and run a timed challenge.
3. Use Predict & Test as a warm-up quiz, and the 💡 panel to debrief.
4. Finish with the printable report or CSV export for homework.

How the model works

Each chamber is a time-varying elastance: pressure moves between its end-diastolic curve and end-systolic line as the muscle activates and relaxes (time constant τ). The chambers connect to a proximal aorta, systemic arteries and veins, pulmonary arteries and veins. Valves have separate forward and backward orifices with Bernoulli losses. A pericardium couples all four chambers. Breathing changes pleural and abdominal pressure. Coronary O₂ supply comes from diastolic perfusion pressure and diastolic time, and demand from the pressure–volume area. Lactate follows oxygen extraction and perfusion pressure. Devices use pump pressure–flow curves, and drugs act through saturating dose–response curves. The model integrates at 10 kHz, conserves blood volume exactly, and was stress-tested with hundreds of randomized extreme patients.

Limits & disclaimer

• It is a lumped teaching model. Real patients vary, and numbers are approximations designed to teach direction and mechanism.
• Not modelled (yet): HOCM/LVOT obstruction, PDA, programmed pacing, PA catheter balloon, heart sounds, named commercial device models.

Pulse Lab is an educational model built by Myocognia. It is not a medical device, is not validated for clinical decisions, and must not be used to diagnose or treat patients. In an emergency, call your local emergency number.