Summary of "ANAESTHETIC SCAVENGING SYSTEM- PHYSICS SERIES"
Summary of "ANAESTHETIC SCAVENGING SYSTEM - PHYSICS SERIES"
This video, presented by Dr. Phil, discusses the Anesthetic Scavenging System, focusing on its purpose, sources of pollution, exposure limits, methods to minimize pollution, quality control, and classification of scavenging systems. The video explains the physics and practical aspects of collecting and safely disposing of waste anesthetic gases in operating theaters to protect healthcare workers and the environment.
Main Ideas and Concepts
1. Purpose of Scavenging
- Required by law to control substances hazardous to health.
- Protects the local environment by venting pollutant gases unchanged into the atmosphere.
- Waste anesthetic gases are potent greenhouse gases and may pose health hazards.
- No strong evidence links trace exposure in operating theaters to adverse health effects, though some weak associations (e.g., spontaneous abortion, hematological malignancies) have been suggested.
2. Sources of Pollution by Anesthetic Gases
- Incomplete scavenging from ventilators or APL valves.
- Leaks from equipment: facemasks, endotracheal tubes, Soda-Lime Canisters, cardiopulmonary bypass circuits.
- Failure to turn off vaporizers or fresh gas flow post-anesthesia.
- Spillage during vaporizer filling.
- Exhaled gases in operating theaters, corridors, and recovery rooms.
3. Maximum Permitted Exposure Levels
Expressed as an 8-hour time-weighted average. Exposure limits vary between countries (UK vs. US) due to lack of robust data.
- Nitrous oxide: UK 100 ppm, US 25 ppm
- Halogenated agents (e.g., isoflurane, sevoflurane): UK 50 ppm, US 2 ppm
- Combined agents + nitrous oxide (US): 0.5 ppm
4. Methods to Minimize Operating Theater Pollution
- Maintain 15-20 air changes per hour with ventilation and air conditioning.
- Use non-recirculating ventilation systems (recirculating systems increase contamination).
- Use Circle Breathing Systems with low or ultra-low fresh gas flows to recycle exhaled gases.
- Employ alternative anesthesia methods (total intravenous anesthesia or regional anesthesia).
- Avoid spillage during vaporizer filling (use fume cupboards or agent-specific connectors).
- Scavenging systems collect and safely dispose of waste gases without affecting patient ventilation.
5. Quality Control and Monitoring
- Annual or quarterly sampling of anesthetic gas concentrations in air.
- Leak tests of equipment and air sampling in operating rooms and personnel breathing zones.
- Preventive maintenance of ventilation and scavenging systems at least yearly.
- Testing includes gas supply, flow meters, and ventilation systems.
6. Classification of Scavenging Systems
Passive Systems
- Simple, no running cost.
- Components: collection system (connected to APL Valve), transfer tubing, receiving system (reservoir bag with pressure relief valves), disposal system (vent to atmosphere).
- Safety features protect against excessive positive/negative pressures.
- Risks include rebreathing if reservoir collapses and contamination if hoses are compressed or occluded.
- Charcoal Canisters (Cardiff Alda's) are passive systems absorbing halogenated agents but not nitrous oxide; require regular replacement.
Semi-Active Systems
- Waste gases conducted to air conditioning extraction points.
- Air conditioning system creates slight negative pressure to assist disposal.
- Variable performance and efficacy.
Active Systems
- Similar collection and transfer components as passive systems.
- Receiving system includes reservoir bag, spring-loaded safety valves, bacterial filter, and visual flow indicators.
- Disposal system uses a fan or pump to create vacuum (30-130 L/min flow rates).
- Mechanisms (motorized fans, pumps, venturi systems) maintain uniform gas flow despite changes in demand.
- Safety features prevent excessive pressures; reservoir bag collapses under excessive negative pressure (risk of rebreathing), and positive pressure may cause barotrauma.
- Vacuum Pump must be dedicated solely to scavenging.
Detailed Methodology / Instructions
Ventilation Requirements
- Ensure 15-20 air changes per hour in operating theaters.
- Use non-recirculating ventilation systems.
- Labor rooms should have at least 5 air changes per hour.
Breathing Systems
- Use Circle Breathing Systems with soda-lime to absorb CO₂.
- Employ low or ultra-low fresh gas flows to reduce anesthetic use and pollution.
Filling Vaporizers
- Fill vaporizers in fume cupboards or use agent-specific connectors to reduce spillage.
Scavenging System Setup
- Connect collection system to APL Valve or ventilator exhaust.
- Use transfer tubing with correct connectors to prevent misconnection.
- Include receiving system
Category
Educational
