Notes on Anesthesia Machines

Introduction

• Speaker: Dr. Hasan Kaur, Senior Resident at Mawlana Medical College, under Dr. Ram Navin Prasad.
• Topic: Anesthesia Machines, discussed in two parts:
  • Boyle Separators
  • Modern Anesthesia Machine

Definition of Anesthesia Machine

• Delivers a fixed proportion of life-sustaining gases (e.g., oxygen) and anesthetic gases (e.g., isoflurane, sevoflurane, desflurane).
• First designed in 1970 by Edmund Gaskin Boyle, known as "Goethe".
• Modern machines referred to as "workstations".

Anesthesia Machine Components

Pressure Systems

• High Pressure System: Contains oxygen at 2000 psig and nitrous oxide at 760 psi.
• Intermediate Pressure System: Reduces pressure from high to low (45-50 psig).
• Low Pressure System: Operates at 5-8 psig above ambient pressure.

High Pressure System Components

1. Hanger Yoke Assembly: For fitting cylinders.
2. Pressure Reducing Valve: Reduces gas pressure (for oxygen and nitrous oxide).
3. Gauges: Indicate cylinder pressure.

Low Pressure System Components

1. APL Valve: Pressure limiting valve.
2. Vaporizers: Mounted on a back bar.
3. Flow Control Knobs: Adjust gas flow.
4. Common Gas Outlet: Where gases exit to the patient.
5. Flow meters: Measure gas flow rates, include nitrous and oxygen.

Intermediate Pressure System Components

• Contains pipeline inlet connections.

Modern Anesthesia Machine Features

• Circle System: Involves inspiratory and expiratory valves, soda lime canisters.
• Oxygen Flush Valve: Delivers high flow (35-75 L/min) for emergencies.
• Nitro-log System: Ensures nitrous oxide flow is contingent on oxygen pressure.
• Safety Features:
  • Color Coding of Cylinders: Prevents mixing of gases (e.g., black and white for oxygen, blue for nitrous oxide).
  • Pin Index Safety System: Prevents incorrect cylinder attachment.
  • Richter Whistle: Alarm for low oxygen levels.

Soda Lime Canister

• Absorbs carbon dioxide using sodium hydroxide.
• Enhances efficiency in gas absorption due to increased surface area from granules.

Electrical Modifications in Modern Machines

• Includes a master switch with UPS for power backup.
• Color-coded pipelines for easy identification.
• Common gas outlets and auxiliary oxygen supply.

Operational Features

• Machines display flow rates and concentrations of gases.
• Parameters such as tidal volume, respiratory rate, and end-tidal CO2 are monitored.
• Low flow anesthesia techniques used for better scavenging and reduced pollution.

Conclusion

• The lecture discussed basic components and safety features of anesthesia machines.
• Future classes will delve deeper into each component and function.