Scavenging System Flashcards
Scavenging definition
collection and removal
- collection of excess gas from the machine delivering anesthesia gases or exhaled by the patient
- removal of these gases out of the working environment
NIOSH recommended levels of Anesthesia gas in OR
anesthetic alone = 2ppm
N20 = 25ppm
anesthetic & N20 = 0.5pmm
5 components of scavenging system
- gas collecting assembly
- transfer means (tubing)
- scavenging interface
- gas disposal tubing
- gas disposal assembly
gas collecting assembly
- collects excess gas at site of emission
- delivers it to the transfer means tubing
*outlet connection should. be 30mm (male fitting)
so it doesn’t fit with any other part of breathing. circuit
transfer means
aka exhaust tubing
- brings excess gas from gas collection assembly to interface
- tubing is short and wide to increase the flow of gas without having to increase pressure
- tubing is kink resistant and color coded (yellow) and stiffer than breathing circuit tubing
- tubing usually has female fitting connector on both ends
scavenging interface
aka balance valve
-prevents delivery of pressures (increased of decreased) from scavenging system to breathing circuit
- limits pressure immediately downstream of the gas collecting assembly to
- 0.5 – +3.5 cm H20
- 30 mm male connector inlet
- should be as close to gas collection assembly as possible
3 basic elements of scavenging interface
- positive pressure relief
- negative pressure relief
- reservoir capacity
Positive pressure relief
in scavenging interface
-protects patient and equipment from occlusion of system
Negative pressure relief
- limits sub atmospheric pressure (negative pressure
Reservoir capacity
capacity matches the intermittent gas floe from gas assembly with the continuous flow of disposal system
-scavenging system is continuously pulling air all the time, reservoir evens out the emptying occurring from the continuous vacuum
2 types of scavenging interfaces
- open (open interface)
- closed (closed 2 types)
- positive pressure relief only
- positive pressure and negative pressure relief
Open interface
No valved -opened to the atmosphere by a relief port
-prevents build up of positive and negative pressure
-vacuum required
*can be adjusted
must have level > excess gas flow rate to prevent pollution to OR
-reservoir (canister ) required
size should be allow for high waste gas flows
-gas enters system at top of canister and flows through a narrow tube to the bottom
Closed
Positive Pressure relief only
-single positive pressure relief valve opens wen max pressure is reached
- *passive disposal
- *no reservoir bag
- no vacuum
-used in remote area and can vent out the window
Closed
Positive Pressure and Negative pressure releif
-positive pressure relief valve
- negative pressure relief valve (2)
- has a backup native pressure relief valve incase first gets occluded
- reservoir bag
- vacuum
- used with active disposal systems, vacuum control valve is adjusted to make sure reservoir bag is not over inflated or completely collapsed
- gas is vented when pressure exceed + 0.5 cmH20
- room air is entrained when pressure is less than - 0.5 cm H20
-backup negative pressure relief valve is open @ -1.8 cmH20
(this should only happen if the primary negative pressure relief valve gets occluded)
gas disposal tubing
- tubing that connects scavenging interface to disposal assembly
- passive system so tubing must be short and wide (increases flow rate)
- tubing must be different size and color than other breathing circuit tubing
- ideal if tubing is running overhead to prevent accidental kinks and obstructions
- DISS connector must be used if connected to an active gas disposal system
