3. Purpose of
Scavenging
Legal requirement
• Control of substance, hazardous to
health (COSHH).
• Only local environment is protected
• The pollutant gases are vented
uncharged to atmosphere
• Most are potent green house gases
4. Possible
Health Hazard
• Some studies have Identified weak
association with exposure to trace amount
of waste anesthetic vapours such as
• Spontaneous abortion.
• Male anesthetists were more likely to
become a father of a daughter than son.
• Hematological malignancies
• Other studies have not replicated these
data
5. Sources of
pollution by
anesthetic
gases and
vapours
• Incomplete scavenging of gases from
• APL Valve
• Ventilator
• Leaks from equipment’s
• Poorly fitting face mask
• T Piece
• Uncuffed trachea
• O rings
• Soda lime canister
• Cryosurgery unit
• Cardiopulmonary bypass circuit
• APL Valve
• Discharge of anesthetic gases from ventilators/vaporizer
• Failure to turn off fresh gas flow/vaporizer at the end
of anesthesia
• Spilling during filling of vaporizer
6. CONT.
• Gas exhaled by patient after
anesthesia
• OR/OT
• Corridors
• Recovery room
7. Maximum
Permitted
Exposure
levels
Expressed as an 8 hours time weighted
average
Different country suggest different data
Values are below the level at which any
significant adverse effects occurred to animal
No evidence or data available to suggest
human health will be adversely affected
8. Maximum
Permitted
Exposure
levels
N2O
• UK 100ppm
• US 25ppm
Enflurane
• UK 50ppm
• US 2ppm
Isoflurane
• UK 50ppm
• US 2ppm
Halothane
• UK 10ppm
• US 2ppm
Sevoflurane
• UK 20ppm
• US 2ppm
Desflurane
• UK 50ppm
• US 2ppm
Halogenated Anesthetic Agents +N20 Us 0.5
9. Method to
minimize OR
pollution
Theater air changes at least 15-20 times per hours
with ventilation and air conditioning
Non recirculating ventilation system usually used
Recirculating system is not recommended.
Non Ventilating OT are 4x are contaminated with
anesthetic gases and vapours compared to those
with adequate ventilation.
10. Cont.
• Use of circle breathing systems
• These low and ultra low flow breathing systems recycle
exhaled anesthetic vapours (rebreathing system).
• There is a mean to absorb exhaled Co2 (soda lime).
• Low fresh gas flow reduces the amount of inhalational
agents used.
• Alternative anesthetic methods to avoid inhalational
anesthetic agents
• Regional anesthesia
• TIVA
11. CONT.
• Avoid spillage of volatile anesthetic agents
when filling vaporizers
• In some country vaporizers are filled with only in
a portable fume cupboard
• Agents' specific connector reduces spillages
• Scavenging
• Collect waste anesthetic gases from the
breathing system and discarding them safely.
• Should not affect ventilation/oxygenation of
the patients
• Should not affect dynamics of the breathing
system
12. CONT.
• Quality Control Procedure
• Sampling to assess waste anesthetic vapor concentration in the air for N2O and
halogenated agents done.
• In UK yearly
• In US quarterly
• Location
• Wherever anesthesia is administered
• Includes
• Leak test of equipment's
• Sampling air in the operation theater personal breathing zone.
• Planned preventive militance programs
• General ventilation system and scavenging equipment should be tested at
least yearly
• Involve anesthetic equipment's gas scavenging gas supply flowmeter and
ventilation system
15. Passive system
Advantages
• Simple to construct
• Zero running cost
Components
Collecting systems
• Should connect to respiratory valve/ expiratory valve
• 30mm connector
• Connect to the transfer tubing
• Prevent accidental misconnection to other ports (safety
features)
Transfer system
• Comprises a wide bore tubing to remove gases.
16. CONT. Receiving system
• Transfer tubing leads to the receiving system
• A reservoir system (reservoir bag)
• A two-spring loaded pressure relieving valves
• Protect against excessive Positive pressure (1kpa)
• In case of obstruction distal to receiving system
• Barotrauma can occur from excessive positive
pressures
• Protect against negative pressure (50 Pa)
• Incase of increasing demand in scavenging system
• Prevent the application of negative pressure to the
patients lungs
• Rebreathing Can occur from collapse of the
reservoir bag due to negative pressure.
Disposal system
• Wide bore copper pipe which lead to atmosphere
17. Mechanism
of action
• Patient spontaneous respiratory efforts
• Mechanical ventilation
Gases are vented to the atmosphere by
• Mounted on the anesthesia machine
• This minimize the length of the transfer tubing and
thus decrease the resistance to gas flow
Receiving system
18.
19. Safety Issues
• If the scavenging system is connected to the exit grille of the theater
ventilation
• Excessive positive or negative pressure at the outlet (by wind at the outlet) will result
in rebreathing and recirculation.
• Reversal of flow (due to wind at the outlet) will result in rebreathing and
recirculation.
• Protect against insects
• By covering the outlet with a wire mesh
• Prevention of compression of the passive hose
• Using non compressible materials
• Not placing the hose on the floor
• Compression/occlusion of the passive hose leads to escape of gases into the theater
20.
21. Semi active system
• The scavenging system may be regarded as semi active if the waste
gases are conducted to the extraction side of the theater air
conditioning.
• The small negative pressure generated by the air conditioning system
assists with disposal of gases from the scavenging tubing.
• These systems have variable performance and efficiency.
23. Components
• Collection system and Transfer system
• The collecting and transfer system
which is similar to that of the passive
system
• Receiving system
• Disposal system
24. Receiving
system
The receiving system is usually a valveless, open-
ended reservoir positioned between the receiving
and disposal components. A bacterial filter
situated between the receiving and disposal
systems can be used. A reservoir bag with two
spring loaded safety valves can also be used as a
receiving system. down stream and a visual flow
indicator positioned
The active disposal system consists of a fan, or a
pump used to generate a vacuum
25. Mechanism
of action
1. The vacuum drives the gases through the system. Active
scavenging systems are able to deal with a wide range of
expiratory flow rates (30–130 L/min).
2. A motorized fan, a pump or a Venturi system is used to
generate the vacuum or negative pressure that is transmitted
through the pipes.
3. The receiving system is capable of coping with changes in gas
flow rates. Increased demands (or excessive negative pressure)
allow ambient air to be entrained so maintaining the pressure.
The opposite occurs during excessive positive pressure. As a
result, a uniform gas flow is passed to the disposal system
26. Problems in practice and
safety features
1. The reservoir is designed to prevent
excessive negative or positive pressures
being applied to the patient. Excessive
negative pressure leads to the collapse of
the reservoir bag of the breathing system
and the risk of rebreathing. Excessive
positive pressure increases the risk of
barotrauma should there be an obstruction
beyond the receiving system.
2. An independent vacuum pump should
be used for scavenging purposes.
27.
28. References
• Al sheikh B et al. essential of anesthetic
equipment's 4th edition
• Alan R atikenhead et al.
• Stephen Boumphery
• Simon Bricker
• Daniel Aston et al.
• Mendonca C et al.
