Scavenging Systems

Question 1

What is the NIOSH recommended limit for anesthetic alone?

Answer 1

2ppm

Question 2

What is the NIOSH recommended limit for Nitrous Oxide?

Answer 2

25ppm

Question 3

What is the NIOSH recommended limit for nitrous oxide and anesthetic together?

Answer 3

0.5ppm

Question 4

What are the five basic components of the scavenging system?

Answer 4

1. Gas collecting assembly
2. Transfer means
3. Scavenging interface
4. Gas disposal tubing
5. Gas disposal assembly

Question 5

What is the diameter of tubing on the gas collecting assembly?

Answer 5

30mm so that it doesn’t connect to other components

Question 6

Between what pressures does the scavenging interface limit pressures?

Answer 6

between - 0.5 and 5 cmH20

Question 7

What is the average difference between Pa CO2 and ETCO2?

Answer 7

PaCO2 is usually 2-5 mmHg higher than ETCO2.

Question 8

What are the components of soda lime?

Answer 8

80% calcium hydroxide
15% H2O
4% sodium hydroxide
1% potassium hydroxide
0.2% silica

Question 9

What is the CO2 capacity of soda lime?

Answer 9

26 L/ 100g of absorbant

Question 10

What are the components of calcium hydroxide lime?

Answer 10

80% calcium hydroxide
16% water
4 % calcium chloride

Question 11

What is the CO2 capacity of calcium hydroxide?

Answer 11

10 L of CO2/ 100 g of absorbant

Question 12

What color does Ethyl violet turn when it is exhausted?

Answer 12

purple

Question 13

What dangerous product can be made when sevoflurane comes in contact with soda lime?

Answer 13

Compound A

Question 14

What product can dry soda lime cause?

Answer 14

CO

Question 15

What is the function of the scavenging interface?

Answer 15

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

Question 16

What are the 3 basic elements of the scavenging interface?

Answer 16

Positive pressure relief, negative pressure relief, reservoir capacity-matches the intermittent gas flow from gas collecting to the continuous flow of disposal system

Question 17

Describe the open scavenging interface.

Answer 17

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

Question 18

What are some advantages/disadvantages of a passive disposal system?

Answer 18

Advantages: inexpensive to set up, simple to operate.
Disadvantages: may be impractical in some buildings

Question 19

What are some advantages/disadvantages of an active disposal system?

Answer 19

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.

Question 20

Describe how to do the check of the scavenging system.

Answer 20

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.

Question 21

Why do we use capnography? What are the contraindications?

Answer 21

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

Question 22

What are two methods of measuring CO2 of expired gases?

Answer 22

colorimetric and infrared absorption spectrophotometry

Question 23

What is the difference between mainstream and sidestream capnography?

Answer 23

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

Question 24

What conditions would cause a slow rise in phase 2 of the CO2 waveform with little or no phase 3?

Answer 24

Obstuctive lung disease like COPD, asthma, bronchoconstriction or acute obstruction

Question 25

What are some causes of CO2 rebreathing?

Answer 25

Equipment dead space, exhausted CO2 absorber, inadequate fresh gas flows

Question 26

What are some causes of rising CO2 with unchanged ventilation?

Answer 26

Malignant hyperthermia, release of tourniquet, release of aortic/major vessel clamp, IV bicard administration, insufflation of CO2 into peritoneal cavity, equipment deffects

Question 27

What are some causes of decreased ETCO2?

Answer 27

Gradual decrease- hyperventilation. Rapid decrease- PE, V/Q mismatch, cardiac arrest, sampling error-disconnects.

Question 28

What are the end products of the CO2 absorber?

Answer 28

water, a carbonate and heat

Question 29

What are the common absorbants?

Answer 29

soda lime, amsorb plus (calcium hydroxide lime) and litholyme (lithium hydroxide)

Question 30

When should you replace absorbant?

Answer 30

When there is 50-70% color change

Question 31

What harmful products can soda lime degrade to?

Answer 31

carbon monoxide if dry, can degrade sevflourane to compound A a nephrotoxic compound