Anesthesia machine 3

Question 1

In the context of Thorpe tube flow dynamics, a low fresh gas flow will favor a ________ flow pattern

Answer 1

laminar

Question 2

At a higher fresh gas flow, the annular space acts like an orifice, creating a _________ flow pattern

Answer 2

turbulent

Question 3

Laminar flow is dependent on

Answer 3

gas viscosity (Poiseuille equation)

Question 4

Turbulent flow is dependent on

Answer 4

gas density (graham’s law)

Question 5

You are administering air 1 L/min and oxygen 3 L/min. Calculate the fraction of inspired oxygen.

Answer 5

80%

Question 6

Describe how to calculate the FiO2 when using a flowmeter.

Answer 6

FiO2= (air flow rate x 21) + (oxygen flow rate x 100)/ total flow rate

Question 7

Describe how to calculate fIo2 when using a nasal cannula.

Answer 7

add 4% FiO2 for every liter of O2 administered (up to a max of 44% FiO2 at 6 L/min)

Question 8

You are using an anesthesia machine that couples fresh gas flow to tidal volume and fully compensates for circuit compliance. Calculate the total tidal volume delivered to the patient.
oxygen= 3 L/min.
air = 1 L/min.
I:E= 1:2
bellows= 500 mL
RR= 10 bpm

Answer 8

632 mL

Question 9

What is the tidal volume delivered to the patient equation?

Answer 9

Vt set on ventilator + FGF during inspiration- volume lost to circuit compliance

Question 10

In flow-coupled anesthesia machines, changes in _________________ impacts the total tidal volume delivered to the patient.

Answer 10

respiratory rate, I:E ratio, FGF, and the height of the bellows

Question 11

If an anesthesia machine does not couple FGF to tidal volume, then

Answer 11

what’s set on the ventilator is what’s delivered to the patient

Question 12

Older anesthesia machines couple FGF to the tidal volume set on the ventilator which

Answer 12

may lead to errors in predicted Vt and minute ventilation

Question 13

Vent changes that increase delivered tidal volume include

Answer 13

decreased RR
increased I:E ratio (from 1:2 to 1:1)
increased FGF
increased bellows height

Question 14

Vent changes that decrease delivered tidal volume include

Answer 14

increased RR
decreased I:E ratio
Decreased FGF
decreased bellows height

Question 15

Increasing the FGF will increase

Answer 15

tidal volume
minute ventilation
and peak inspiratory pressure
should see EtCo2 decrease

Question 16

Decreasing the FGF will decrease

Answer 16

tidal volume
minute ventilation
peak inspiratory pressure
should see EtCo2 increase

Question 17

A ventilator is programmed to deliver a tidal volume of 600 mL. If the breathing circuit compliance is 5 mL/cm H2O and the peak pressure is 25 cmH2O, what is the total tidal volume delivered to the patient?
a. 425 mL
b. 450 mL
c. 475 mL
d. 500 mL

Answer 17

c. 475 mL

Question 18

Define compliance.

Answer 18

compliance is a change in volume for a given change in pressure- it’s a measure of distensibility

Question 19

What is the compliance equation?

Answer 19

compliance= volume/pressure

Question 20

Many modern ventilators ________________ for fresh gas lost to circuit compliance.

Answer 20

automatically compensate

Question 21

When the ventilator produces pressure inside the breathing circuit, some of this gas causes the circuit to expand. Since this doesn’t reach the patient,

Answer 21

it doesn’t contribute to the tidal volume that the patient receives

Question 22

Compliance is a measure of

Answer 22

distensibility

Question 23

The isoflurane dial is set to 2%. What percent of fresh gas exiting the vaporizing chamber is saturated with isoflurane?

Answer 23

100%

Question 24

When you consider the variable bypass vaporizer, think

Answer 24

variable bypass, flow-over, temperature compensated, out-of-circuit, and agent-specific

Question 25

Describe what out of circuit means.

Answer 25

the variable bypass vaporizer is positioned outside of the breathing circuit

Question 26

Describe what is meant by variable bypass.

Answer 26

when fresh gas enters the vaporizer, some of it encounters the liquid anesthetic while the rest bypasses the liquid anesthetic.

Question 27

With a variable bypass vaporizer, by setting the concentration on the dial, you determine

Answer 27

the splitting ratio (i.e. how much fresh gas contacts the liquid anesthetic)

Question 28

Describe what is meant by flow-over.

Answer 28

As the fresh gas enters the vaporizing chamber (liquid anesthetic is here), it flows over a series of baffles and wicks.

Question 29

Baffles and wicks increase _________ & _______________

Answer 29

surface area and turbulence

Question 30

Baffles and wicks ensure that fresh gas inside the vaporizing chamber becomes

Answer 30

100% saturated with the anesthetic agent

Question 31

Variable bypass vaporizers _______________ at changes in elevation

Answer 31

automatically compensate vaporizer output

Question 32

Describe agent-specific.

Answer 32

Each vaporizer is calibrated to one anesthetic agent- filling a vaporizer with the incorrect anesthetic can lead to catastrophic errors in output

Question 33

Describe temperature-compensated.

Answer 33

The temperature compensating valve adjusts the ratio of vaporizing chamber flow to bypass flow and guarantees a constant vaporizer output over a wide range of temperatures

Question 34

Setting a higher concentration directs more fresh gas towards _____________

Answer 34

the liquid anesthetic

Question 35

Setting a lower concentration directs

Answer 35

less fresh gas towards the liquid anesthetic

Question 36

Flows less than _________ or greater than __________ can lead to reduced vaporizer output

Answer 36

200 mL/min or greater than 15 L/min.

Question 37

If the vaporizer is tipped over some of the liquid anesthetic may enter

Answer 37

the bypass chamber leading to increased vaporizer output

Question 38

1 mL of liquid anesthetic produces _________ of anesthetic vapor

Answer 38

200 mL

Question 39

If the vaporizer is tipped, then you should run a high FGF through it for

Answer 39

20-30 minutes before it can be used for a patient

Question 40

The pumping effect can

Answer 40

increase vaporizer output

Question 41

Anything that causes gas that has already left the vaporizer to re-enter the vaporizing chamber can cause

Answer 41

the pumping effect

Question 42

The pumping effect is enhanced by

Answer 42

low fresh gas flows, low concentration dial setting, low levels of liquid anesthetic in the vaporizing chamber, positive pressure ventilation, and the use of the oxygen flush valve

Question 43

The pumping effect is minimized by

Answer 43

modern vaporizer design

Question 44

The most common cause of a vaporizer leak is

Answer 44

a loose filler cap

Question 45

The most common location for a leak to occur in the low-pressure system is

Answer 45

an internal leak in the vaporizer

Question 46

A leak can only be detected when

Answer 46

the vaporizer is turned off

Question 47

What is the equation to calculate how much liquid anesthetic is used?

Answer 47

mL of liquid anesthetic used per hour= Vol% x FGF (L/min) x3

Question 48

Setting the vaporizer to __________ eliminates the worry of tipping the vaporizer during transport or removal

Answer 48

transport mode (T)