Scavenging Systems Flashcards
Why is scavenging necessary?
reduce exposure to anesthetic gases, oxygen rich environment has risks
If you can smell anesthetic on pt’s breath after extubation how many ppm is the anesthetic on their breath?
30 ppm
What organization sets standards for scavenging?
National Institute for Occupational Safety
What are the recommended time weighted average (TWA) maximum concentrations of the following medical gases? a) halogenated anesthetic alone b) N2O c) halogenated w/ N2O
a) 2 ppm b) 25 ppm c) 0.5 ppm
What is time weighted average?
sampling of exposure to OR gases that evaluated the average concentration of anesthetic gas over prolonged time (1-8 hrs)
What 4 things determine how much exposure you have to anesthetic gas?
OR ventilation, functionality of anesthesia equipment (machine check), effective scavenger system, anesthetic technique
What are some aspects of anesthetic technique that affect exposure to OR gases? (6)
failure to turn off gas flow, poorly fitting mask, flushing circuit when not connected to pt, filling the vaporizers, uncuffed ETT, breathing circuits
What 3 interventions can you implement to avoid risks of exposure to volatile gases?
no N2O, TIVA, regional anesthesia
What are 5 basic components of scavenger system?
gas collecting assembly, transfer tubing, scavenging interface (open vs closed), gas disposal tubing, gas disposal assembly (active vs passive)
What is the purpose of the gas collecting assembly?
collects gases from breathing circuit and delivers them to the transfer tubing
Where is the gas collecting assembly in spont vent? What about in mech vent?
Spont: at APL valve Mech vent: at ventilator spill valve or pressure relief valve
What is purpose of the APL valve and ventilator spill valve?
controls how much gas left in circuit and how much released to scavenger
Why is the size of the connections in the gas collection assembly important and what is the size?
to prevent misconnections, 30 mm (19 mm in older machines) male
Whats the function of the transfer tubing?
It beings gas from collecting assembly to scavenging interface.
What are some features of transfer tubing? (4)
30 mm female connections (both ends), short length and large diameter (reduces resistance, carries high flow of gas w/ increase in pressure), kink resistant, different in appearance from breathing tubes
What is the purpose of the scavenging interface (AKA balancing valve/balancing device)?
prevents increase or decreases in pressure in the scavenging system from transferring to the breathing system
What is the most critical component of the scavenging interface?
scavenging interface
What would happen if scavenging system removes too much gas? Too little?
negative pressure. barotrauma/positive pressure
What pressures do the scavenging interface limit downstream of the gas collecting assembly?
- 0.5 - 3.5 cmH2O
What are the features of the scavenger interface? (5)
inlet 30 mm male connector, close to gas collecting assembly, positive press relief (in case of occlusion), negative press relief (in case of subatmospheric pressure), reservoir capacity (matches intermittent flow of gas collecting assembly to continuous flow of disposal of gases)
What two types of scavenger interface are there?
open or closed
What are the features of open scavenger interface? (4)
no need for positive/negative pressure relief valves, open to atmosphere via relief ports in reservoir (avoids build up of pressure +/-), has a reservoir, has adjustable vacuum
On an open scavenger interface what must be the level of vacuum suction be set to? Why?
> than excess gas flow rate, to prevent OR pollution
What happens if suction is too high on scavenger interface? Too low?
high: entrains room air into scavenger low: vents scavenged gas into OR
How many types of closed scavenger interface are there? What are their names?
2: positive press/negative press relief and positive press relief only
What are some features of closed scavenger positive and negative pressure relief interface?
positive pressure relief valve, negative pressure relief valve, reservoir bag, vacuum (active)
What are the pressure limits in a closed scavenger system that has a positive and negative pressure relief interface?
-0.5 cmH2O (back up relief valve -1.8 cmH2O) and +0.5 cmH2O
What are some features of a positive pressure relief only scavenger interface?
single valve (positive pressure), passive disposal (no vacuum), no reservoir bag (absence of vacuum and reservoir eliminates need for negative pressure relief)
What is the difference between a closed and open scavenger interface?
open: communication w/ OR closed: no communication w/ OR
What is the purpose of the gas disposal tubing?
Connects scavenging interface to disposal assembly
What are some features of gas disposal system?
tubing different size and color from breathing system, hose short/wide (prevents obstruction/kinking), DISS connector (gas disposal system)
How many types of gas disposal assemblies are there? What are they?
2 types. Active (acts on negative pressure), Passive (needs positive pressure, above atmospheric)
Describe how a passive gas disposal assembly work?
waste gases are directed out of building through a pipe passing through wall, extractor fan vented to outside air.
What are the advantages of a passive gas disposal assembly? Disadvantages?
inexpensive to set up and simple to operate. impractical in some settings.
Describe how an active gas disposal assembly works?
system is connected to exhaust of breathing system to the hospital vacuum system and controlled via needle valve
What are the advantages of an active gas disposal assembly? Disadvantages?
convenient in large hospitals w/ many machines in use in many different locations. majorly expensive. needle valve may need continual adjustment.
What type of facility is an active gas disposal assembly most common?
hospitals
