15/02/2026
🚨 “One wrong cylinder. One fatal mistake.”
This image behind me?
It’s not just a picture.
It’s a classic viva trap — and a real-life safety checkpoint in the OT.
I’m Dr. Azam, Senior Consultant Anaesthesiologist and Critical Care Specialist, and Academic Head at Bhagwan Mahaveer Jain Hospital. I’ve seen this question asked again and again — in theory exams, viva voce, and machine checks — and yet many students freeze.
Let’s break it down simply 👇
This is the Pin Index Safety System.
🔹 Introduced by Dr. Philip Woodbridge in 1952
🔹 Used for small cylinders (A–E)
🔹 Prevents the wrong gas cylinder from being connected to the anaesthesia machine
📌 High-yield exam pearls:
• Memorise the pin positions (2–5 = Oxygen, 3–5 = Nitrous Oxide)
• Know the special combinations for O₂ + CO₂, O₂ + Helium
• Be ready to answer: What are the fallacies of the pin index system?
Why does this matter?
Because patient safety starts before induction — and examiners love testing systems that save lives.
👉 Save this post
👉 Revise it before exams
👉 Learn anaesthesia the way it’s tested and practiced
📚 More such exam-focused concepts at barcdoctorazam.com
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