Anesthesia Equipment, Monitoring, and Safety
Equipment, monitors and safety systems
The Anesthesia Equipment, Monitoring, and Safety domain tests the anesthesia machine, breathing circuits, vaporizers, gas supply, scavenging and monitor interpretation. Safety questions often ask what happens when oxygen supply fails or an alarm sounds.
- Oxygen fail-safe: if oxygen pressure falls, the machine reduces or cuts nitrous oxide and alarms. It does not guarantee oxygen flow; check the backup cylinder.
- Vaporizer interlock prevents two volatile agents from being delivered. Agent-specific filling reduces misfilling; desflurane vaporizers are heated and pressurized.
- Breathing circuit leak test: close the adjustable pressure-limiting valve, occlude the Y-piece, pressurize to about 30 cm H2O, and confirm a stable pressure. A falling pressure means a leak.
- Soda lime exhaustion: rising inspired CO2, color change (not reliable alone), and increased heat. Replace absorbent.
- Capnography is mandatory for intubation confirmation and continuous ventilation monitoring. A normal waveform has inspiratory, expiratory upstroke, alveolar plateau and inspiratory downstroke.
- Pulse oximetry lags behind arterial saturation and is unreliable with poor perfusion, motion, methemoglobin and carboxyhemoglobin.
- Scavenging removes waste anesthetic gas; check connections and flow.
Worked example
During a leak test, pressure reaches 30 cm H2O but falls to 10 cm H2O within 10 seconds. The reasoning: a stable pressure is required; a rapid fall indicates a leak in the circuit, Y-piece, CO2 absorber or machine. Do not anesthetize until the leak is found and corrected or a self-inflating bag is immediately available.
Traps that cost marks
Silencing an alarm without assessing the patient is a classic error. Do not confuse end-tidal CO2 with arterial CO2 in low-perfusion states. Do not assume the oxygen analyzer is optional; it detects hypoxic mixtures.