A size E oxygen cylinder is being attached to the yoke of a portable anaesthesia machine. The pin index safety system is designed to prevent wrong cylinder attachment. Which pair of pin positions is unique to an oxygen cylinder?
- A Pins 2 and 5 ✓
- B Pins 1 and 6
- C Pins 3 and 5
- D Pins 4 and 6
Correct answer: A. Pins 2 and 5
Explanation
The pin index system uses pins on the yoke that align with holes drilled in the cylinder valve face. Oxygen is assigned holes at positions 2 and 5. Carbon dioxide uses 1 and 6, nitrous oxide uses 3 and 5, and entonox uses 4 and 6. This mechanical coding makes it impossible to connect a cylinder to the wrong yoke unless the pins are deliberately damaged or removed.
Reference: Morgan and Mikhail's Clinical Anesthesiology, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.