Vaporizers

Question 1

Pressure exerted by the molecules of vapor is the

Answer 1

saturated vapor pressure

Question 2

As temperature increases

Answer 2

vapor pressure increased

Question 3

atmospheric pressure

Answer 3

is the boiling point

Question 4

Isoflurane boiling point

Answer 4

48.5C (119.3F)
VP 238

Question 5

Sevoflurane boiling point

Answer 5

58.5C (137.3)
VP 170

Question 6

Desflurane boiling point

Answer 6

22.8C (73.04F)
VP 669

Question 7

temperature-compensated

Answer 7

vaporizer that is equipped to self-adjust to maintain a constant output over a wide range of operating temperatures

Question 8

Factors that influence vaporizer output

Answer 8

Flow rates less than 250 ml per minute or greater than 15 LPM

Temperature – modern vaporizer construction minimizes the effect of temperature changes

Intermittent back pressure – older vaporizer models may be sensitive to use of the flush valve, high respiratory rates or high peak inspiratory pressures

Carrier gas composition – suddenly adding high concentration of N2O may cause transient reduction in vaporizer output because nitrous is more soluble in the volatile agents than O2

Question 9

Essential parts of the vaporizer

Answer 9

Concentration control dial
Bypass chamber (handles > 80% of the flow)
Vaporizing chamber (handles < 20% of the flow)
Filler port and cap
Fill level gauge
Drain

Question 10

Modern Vaporizers

Answer 10

1. variable bypass
2. flow-over
3. temperature-compensated
4. agent-specific
5. out of breathing circuit

Question 11

Vaporizer Hazards (Older Equipment)

Answer 11

Misfilling (wrong agent) – esp. older equipment

Contamination – fouled agent

Tipping (rare problem)

Overfilling – esp. older equipment

Under filling or dry vaporizer

Simultaneous inhaled anesthetic administration (older equipment without vapor-interlock system)

Leaks – environmental contamination

Question 12

Desflurane Vaporizer characteristics

Answer 12

Tech 6

High vapor pressure – boils at 22.8° C (73°)
“highly volatile”

Desflurane easier to control if the agent is heated to 39° C which pressurizes it to almost 2 atmospheres (~ 1300 mmHg)

Tec-6 is described as a dual-gas blender rather than a variable bypass vaporizer

only one that has alarms for filling or not working.

require electricity

Question 13

Altitude impact on vaporizers

Answer 13

Concentration output almost doubles (97%) but PP output only increases by 29%

Ambient pressure changes affect vaporizer output in terms of concentration output

With variable bypass vaporizers, partial pressure ratios change only a small amount over a range of altitudes

does not apply to desflurane and the dual gas blender vaporizer which does not provide a consistent partial pressure at varying altitudes