Scavenging Systems Flashcards
What is the NIOSH recommended limit for anesthetic alone?
2ppm
What is the NIOSH recommended limit for Nitrous Oxide?
25ppm
What is the NIOSH recommended limit for nitrous oxide and anesthetic together?
0.5ppm
What are the five basic components of the scavenging system?
- Gas collecting assembly
- Transfer means
- Scavenging interface
- Gas disposal tubing
- Gas disposal assembly
What is the diameter of tubing on the gas collecting assembly?
30mm so that it doesn’t connect to other components
Between what pressures does the scavenging interface limit pressures?
between - 0.5 and 5 cmH20
What is the average difference between Pa CO2 and ETCO2?
PaCO2 is usually 2-5 mmHg higher than ETCO2.
What are the components of soda lime?
80% calcium hydroxide 15% H2O 4% sodium hydroxide 1% potassium hydroxide 0.2% silica
What is the CO2 capacity of soda lime?
26 L/ 100g of absorbant
What are the components of calcium hydroxide lime?
80% calcium hydroxide
16% water
4 % calcium chloride
What is the CO2 capacity of calcium hydroxide?
10 L of CO2/ 100 g of absorbant
What color does Ethyl violet turn when it is exhausted?
purple
What dangerous product can be made when sevoflurane comes in contact with soda lime?
Compound A
What product can dry soda lime cause?
CO
What is the function of the scavenging interface?
To prevent pressure increases or decreases in the scavenging system from being transmitted to the breathing system. The interface limits pressures immediately downstream of the gas-collecting assembly to between -0.5cmH20 to 5 cm H2O
What are the 3 basic elements of the scavenging interface?
Positive pressure relief, negative pressure relief, reservoir capacity-matches the intermittent gas flow from gas collecting to the continuous flow of disposal system
Describe the open scavenging interface.
No valves, open to the atmosphere via holes, requires a vacuum that must be set in excess of the gas flow rate to prevent OR pollution
What are some advantages/disadvantages of a passive disposal system?
Advantages: inexpensive to set up, simple to operate.
Disadvantages: may be impractical in some buildings
What are some advantages/disadvantages of an active disposal system?
Advantages: convenient in large hospitals where many machines are in use in different location. Disadvantages: vacuum system and pipework is a major expense, needle valve may need continual adjustment.
Describe how to do the check of the scavenging system.
Ensure proper connections between the APL valve and scavenging system as well as between the ventilator relief valve and the scavenging system. Fully open the APL valve and occlude the Y-piece. With minimum O2 flow make sure the scavenger reservoir bag collapses completely and the pressure gauge reads zero. With O2 flush fully activated allow the scavenger bag to distend fully and make sure the pressure gauge reads less than 10cm H20.
Why do we use capnography? What are the contraindications?
Gold standard to confirm ETT placement, to determine if the patient is being ventilated, to guide ventilator settings, to detect abnormalities (pulmonary embolism, disconnect, malignant hyperthermia, obstructive airway). There are no contraindications
What are two methods of measuring CO2 of expired gases?
colorimetric and infrared absorption spectrophotometry
What is the difference between mainstream and sidestream capnography?
Mainstream uses a heated infrared device that is placed in the circuit, there is less time delay, potential for burns, sensor window must be clear of mucous.
Sidestream- a fixed amount of gas is aspirated and transported to sampling cell via tubing, there is a time delay and it is a potential disconnect source
What conditions would cause a slow rise in phase 2 of the CO2 waveform with little or no phase 3?
Obstuctive lung disease like COPD, asthma, bronchoconstriction or acute obstruction
What are some causes of CO2 rebreathing?
Equipment dead space, exhausted CO2 absorber, inadequate fresh gas flows
What are some causes of rising CO2 with unchanged ventilation?
Malignant hyperthermia, release of tourniquet, release of aortic/major vessel clamp, IV bicard administration, insufflation of CO2 into peritoneal cavity, equipment deffects
What are some causes of decreased ETCO2?
Gradual decrease- hyperventilation. Rapid decrease- PE, V/Q mismatch, cardiac arrest, sampling error-disconnects.
What are the end products of the CO2 absorber?
water, a carbonate and heat
What are the common absorbants?
soda lime, amsorb plus (calcium hydroxide lime) and litholyme (lithium hydroxide)
When should you replace absorbant?
When there is 50-70% color change
What harmful products can soda lime degrade to?
carbon monoxide if dry, can degrade sevflourane to compound A a nephrotoxic compound
