Each scenario breaks exactly one part of the machine, the circuit, or the patient interface. Nothing tells you which. Watch the waveforms and the measured numbers, decide what is broken, then read the explanation. Every explanation is written for someone on their first week of residency.
How hard a case feels depends on the screen-detail level set on the machine tab. On Beginner you get two tracings, six numbers and a choice of four parts; on Intermediate, four tracings, the gas pathway map and twelve parts; on Everything, the full console and all 55 parts. The same case is worth doing again at a higher level.
Things the simulator cannot show you by moving a dial: gas physics, absorber chemistry, scavenging, cylinder maths, safety interlocks and the checkout. One answer each, with the reasoning spelled out.
If something here didn't answer your question — or the machine did something the simulator doesn't reproduce — write it down. It goes straight to Dr. Bronshteyn.
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An anesthesia machine does two separate jobs. First, it mixes fresh gas — oxygen, air or nitrous oxide, plus anaesthetic vapour — and pours it into the breathing circuit. Second, a ventilator pushes gas from that circuit into the lungs and lets it come back out. Almost every machine fault is a fault in one of those two jobs, and the two jobs have different fingerprints: fresh-gas problems change the concentrations you measure (O₂, CO₂, agent), and ventilator/circuit problems change the waveforms and volumes.
This is how hard the machine is pushing, measured in centimetres of water. In volume control it climbs in a straight ramp during inspiration, reaches a peak, then — if you dial in an inspiratory pause — drops to a flat plateau and holds there before falling back to PEEP.
Peak pressure is the pressure needed to overcome the tubes plus the lungs. Plateau pressure is the pressure needed to hold the lungs open once gas has stopped moving. So:
How fast gas is moving, in litres per minute. Above the line is gas going in, below the line is gas coming out. In volume control the inspiratory part is a flat-topped square; in pressure control it is a tall spike that decays. The expiratory part is always a passive downward spike that decays back to zero.
Two things to look for: does the expiratory flow return all the way to zero before the next breath starts (if not, gas is being trapped), and is the expiratory spike blunted and long (obstruction)?
Volume in the lungs during the breath. It should rise to your set tidal volume and come back to the same baseline it started from. If the curve comes down but never reaches the baseline, gas that went in is not coming back out — that is a leak in the circuit, around the tube cuff, or into a chest drain.
The single most informative tracing on the machine. A normal one is a rectangle with a slightly tilted top: a flat baseline at zero, a steep upstroke, a nearly flat plateau, the highest point of which is end-tidal CO₂, then a steep fall back to zero as fresh gas washes the sensor.
The left panel is what you asked for. The right panel is what the machine actually sensed. A well-behaved machine makes them agree. Every scenario in this app is a version of one question: which single part could make these two panels disagree in exactly this way?
When something goes wrong and you do not yet know what: hand-ventilate with 100% oxygen from a source you trust. Switch to the bag, turn the O₂ flush on, feel the compliance in your own hand, look at the chest, look at the capnogram. Squeezing the bag yourself instantly separates "the machine is broken" from "the patient is broken", and it buys you the time to work out which part it was.
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© 2026 Yuriy Bronshteyn, MD, FASE
Pick one. You can also click the part directly on the gas-pathway diagram.