Physics, Monitoring, and Anesthesia Delivery Devices Flashcards

1
Q

How do you calculate vaporizer output?

A

vaporizer output = carrier gas flow x SVP

Patm - SVP

**SVP: saturated vapor pressure of anesthetic gas**

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2
Q

What are the components of Poiseuilles’s equation for laminar flow through a tube?

A

flow = πr4 x deltaP

8 x viscosity x L

L: length of tube

deltaP: driving pressure

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3
Q

What is the pressure and volume in a full oxygen cylinder?

A

2200 psi
700 L

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4
Q

What is the pressure and volume in a full nitrous oxide cylinder?

A

750 psi
1600 L

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5
Q

What is the pressure from the wall source of oxygen or nitrous oxide?

A

50 psi

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6
Q

What does the first stage pressure regulator bring the pressure from the O2 and nitrous oxide tanks down to?

A

45 psi

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7
Q

When does the pressure in a nitrous oxide tank start to fall?

A

When it is 75% depleted (i.e., 400 L)

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8
Q

How do you convert g of nitrous oxide to L?

A

44 g = 22.4 L

** Avogadro’s hypothesis: 1 mole takes up 22.4 L **

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9
Q

What is the SVP (saturated vapor pressure) of the common anesthetic gases?

A

sevoflurane: 160 mmHg
enflurane: 172 mmHg
isoflurane: 240 mmHg
halothane: 243 mmHg
desflurane: 680 mmHg

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10
Q

How is radiation risk related to distance from the source?

A

radiation risk is inversely proportional to (distance from the source)2

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11
Q

What is the Reynold’s number the distinguishes laminar and turbulent flow?

A

< 2000 is laminar

>2000 is turbulent

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12
Q

Which type of flow is most dependent on gas/fluid viscosity? Density?

A
  • Turbulent flow depends on density
  • Laminar flow depends on viscosity
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13
Q

How is flow different at the top and the bottom of the flowmeter?

A
  • Upper part of the flowmeter has turbulent flow
  • Lower part of the flowmeter has laminar flow
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14
Q

What color are gas cylinders in the US?

A

oxygen - green

nitrous oxide - blue

air - yellow

carbon dioxide - gray

nitrogen - black

helium - brown

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15
Q

What are the causes of rebreathing in the circle system?

A
  • exhausted CO2 absorbent
  • incompetent expiratory valve (more common)
  • incompetent inspiratory valve (less common)
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16
Q

How should you manage a failure in the pipeline oxygen supply?

A

Turn off the ventilator and manually ventilate with low flows as the ventilator is oxygen-powered and will drain your supply faster.

17
Q

How do you first detect an expiratory limb disconnection during spontaneous ventilation?

A

inspired oxygen concnetration will fall

(etCO2 will remain normal for a while)

18
Q

What problems occur with soda lime particles that are too large?

A

rebreathing due to inadequate contact surface area with expired gases and channeling

19
Q

What problems occur with soda lime particles that are too small?

A

increased resistance to breathing

20
Q

Which Mapleson circuit is best for spontaneous ventilation?

A

Mapleson A

21
Q

Which Mapleson circuit is the best for controlled ventilation?

A

Mapleson D

22
Q

What does the saturated vapor pressure of a substance depend on?

A

physical characteristics of the liquid

temperature

** NOT barometric pressure **

23
Q

How do you adjust the dial setting for desflurane at high altitude?

A

dial settingDenver = dial settingsea level x 760

Patm

24
Q

What does the negative pressure relief mechanism do?

A

Prevent an active scavenging system from removing too much gas from the breathing circuit and creating negative pressure.

25
Q

What causes a negative pressure alarm?

A
  • spontaneous respiration with a circuit obstruction
  • excessive flow through an active scavenger system
  • application of a suction catheter to the ETT
26
Q

What can be measured with an infrared analyzer?

A

CO2, N2O, and volatile anesthetics

** not O2 as at least 2 dissimilar atoms are required **

27
Q

What analyzers are used in an ABG?

A

pH - Sanz electrode

PaCO2 - Severinghaus electrode

PaO2 - Clark (polarographic) electrode

28
Q

What can be used to meaure oxygen in a mixture of gases?

A

fuel cell

paramagnetic analyzer

29
Q

How do cmH2O convert to mmHg?

A

10 cmH2O = 7.5 mmHg

30
Q

How does a pressure transducer convert mechanical energy into electrical energy?

A

a strain gauge and a Wheatstone bridge circuit

31
Q

What does the line isolation monitor (LIM) do?

A

monitors the integrity of ungrounded power sources in the OR, preventing macroshock (NOT microshock)

32
Q

What should be done if the line isolation monitor alarms?

A

before a procedure has begun: postpone or move procedure

after a procedure has begun: unplug devices, starting with most recently plugged in

33
Q

What is the critical temperature?

A

the temperature above which a gas cannot be converted to a liquid by any amount of pressure

(** critical pressure is the pressure at critical temperature **)

34
Q

What is the difference between absolute and relative humidity?

A

absolute humidity - amount of water vapor present at a given temperature (gm %)

relative humidity - amount of water vapor present / amount of water vapor needed for full saturation (at a given temperature)

35
Q

At what minimum fresh gas flow rate is CO2 absorbent not needed to prevent CO2 rebreathing?

A

5 L/min

36
Q

What is the amperage difference between macroshock and microshock?

A

macroshock: > 100 mAmps
microshock: 10-100 mAmps

37
Q

What is the classic scenario for microshock?

A

A shock traveling through monitoring equipment with a short circuit to a PA catheter, CVP line, pacemaker, or external pacing wire leading to an inadvertent shock applied to the heart