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I&M Final > Respiratory Gas Analysis > Flashcards

Respiratory Gas Analysis Flashcards

1
Q

*Datex Capnomac Ultima and GE Compact Airway Module

A

Infrared analysis of CO2, N2O, and anesthetic agents

Paramagnetic analysis of O2

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2
Q

Why monitor respiratory gases?

A 
Capnography 
Breathing circuit problems 
End Tidal AA – estimate alveolar concentration
Adequacy of pre-oxygenation
Anesthesia machine failures/malfunctions
Physiologic events – bronchospasm, etc.
Gas supply problems
Gas uptake and production
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3
Q

*Gas Sampling Techniques

A

Side stream and main stream

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4
Q

*Side Stream

A

A diverting analyzer that withdrawals samples

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5
Q

*Side Stream sampling flow and response time

A

50-250 ml/min

300 ms

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6
Q

Main Stream

A

Infrared light beam passed through the airway

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7
Q

T/F Water trap should be emptied periodically to prevent water from entering the monitor

A

True

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8
Q

*T/F In non diverting systems there is a cuvette with a window through which the infrared light passes

A

True

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9
Q

What becomes a concern if the water trap is located beneath the vaporizer?

A

That liquid anesthetic agent will damage the plastic that makes up the trap

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10
Q

Placing the sample line on the patient side of the HME vs. the breathing system side

A

Patient side: More accurate CO2 reading, but can accumulate more water and/or become contaminated
Breathing system side: CO2 value is much lower

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11
Q

T/F Loosely fitting oxygen masks and nasal cannula are not a useful method of measuring carbon dioxide

A

False

They are not accurate, however they are still a useful method of assuring that the patient is breathing

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12
Q

*T/F Gas sampling lines located near the convergence of the inspiratory and expiratory limbs can show an inaccurately high CO2 reading

A

False

It would show an inaccurately low reading due to dilution via the inspiratory gas

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13
Q

Automatic vs. manual select agent identification

A

Automatic: Display multiple agents simultaneously and detect contaminated vaporizers
Select Agent: Cannot display multiple agents, but much less expensive

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14
Q

*Techniques used to analyze oxygen and their response times

A

Polarographic: 3-15 seconds
*Fuel Cell: 5-35 seconds (Lifespan 200,000 % hours/~15 months in room air)
*Paramagnetic: 150 msec
Mass Spectrometry: 40-50 msec

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15
Q

What the heck are % hours?

A

Percent hours mean that the larger the concentration of oxygen being analyzed, the shorter the life of the sensor

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16
Q

*Polarographic: Clark Electrode

A

The amount of current gener­ated as oxygen is reduced is proportional to the amount of oxygen present in the gas mixture
Require applied voltage or *galvanic cell (most common)

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17
Q

Oxygen Fuel Cell

A

Contains a temperature compensating thermistor and a variable resistor

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18
Q

CO2 Electrode (Severinghaus)

A

Utilizes a CO2-sensitive glass electrode in a surrounding film of bicarbonate solution covered by a thin plastic carbon dioxide permeable membrane, but impermeable to water and electrolytic solutes. The carbon dioxide pressure of a sample gas or liquid equilibrates through the membrane and the glass electrode measures the resulting pH of the bicarbonate solution.

19
Q

Paramagnetic Oxygen Analyzer

A

Utilizes the strong magnetic property of oxygen (200 times greater than other anesthetic gases)

20
Q

Paramagnetic Oxygen Analyzer: Two techniques

A

Dumbbell (magnetodynamic) (Linus Pauling) (Direct Reading, Null Deflection)
Differential Pressure

21
Q

Null Deflection

A

A dumbbell with two nitrogen-containing spheres is suspended in a magnetic field. The dumbbell experiences torque proportional to the oxygen concentration within the analyzer. The restoring force needed to counteract the torque is used to calculate the PO2

22
Q

Direct Reading

A

Like null deflection, except that the movement of the dumbbell is used to give the oxygen concentration directly

23
Q

*Differential Pressure (magnetpneumatic)

A

A reference gas and the unknown gas a pumped through the analyzer and converge into a tube at the outlet. The gases are separated by the differential pressure analyzer. A magnet is turned on and off rapidly, causing the pressure in the paths of the gasses to differ. The resulting pressure difference is then detected by the analyzer.

24
Q

*Transcutaneous Oxygen Measurement: Heating

A

*If the skin is heated locally to 43-44 deg. C, then the peripheral vessels dilate, the O2 consumption in the skin is negligible, and the skin and capillary tensions become a reasonable estimation of arterial tension

25
Q

*Transcutaneous Oxygen Measurement: The complete system

A

Polarographic electrode

26
Q

*Transcutaneous Oxygen Measurement: Burns

A

Skin temperatures above 45 deg. C

27
Q

*Transcutaneous Oxygen Measurement: Changing position

A

Every 3-6 hours to avoid burns

28
Q

*Why are the oxygen inspired and expired values different from the calculated FiO2?

A

They are displaying PaO2

29
Q

Laser Doppler Blood Perfusion Monitoring and tcpO2/tcpCO2

A

Permits multiple channels of pressure monitoring and laser Doppler with site temperature control and heat provocation

30
Q

Infrared Spectroscopy

A

Absorption of infrared radiation results in excitation of vibrational, rotational and bending modes (molecule remains in electronic ground state)

31
Q

What type of molecules can be measured using infrared spectroscopy?

A

Asymmetric Polyatomic Molecules

32
Q

Which gases can be measured using infrared spectroscopy?

A

Carbon Dioxide, Nitrous Oxide, Halothane, Enflurane, Isoflurane, Desflurane, Sevoflurane, Nitric Oxide, Water Vapor

33
Q

Water absorbed what wavelengths?

A

~300 and 625

34
Q

T/F Water vapor can effect the accuracy of many gas analyzers

A

True

35
Q

Volumes Percent

A

Partial Pressure (mmHg) / Total Pressure (mmHg) * 100

36
Q

T/F Infrared analyzers measure the partial pressure of a gas

A

True

37
Q

IR (NDIR) Measuring Bench IR beam is interrupted electronically rather than mechanically by what?

A

Chopper wheel

38
Q

*Balance Gas

A

The sum of the analyzed gases subtracted from the ambient pressure
Essentially, the partial pressure of the unmeasured gas
Often nitrogen

39
Q

Mass Spectrometry

A

Fragmentation of the molecule by an electron beam

40
Q

How does Mass Spectrometry work?

A

Produces a positive ion whose path is determined by the mass to charge ratio (m/e)
Positive ion lands on a collector creating an electrical current (Fixed magnetic sector, Quadrapole)

41
Q

*In Mass Spectrometry, the positive ion’s path is determined by what?

A

The mass to charge ratio (m/e)

42
Q

Mass Spectrometry can measure which gases?

A

Oxygen, Nitrogen, Carbon Dioxide, Helium(?), Nitrous, Oxide, Halothane , Enflurane, Isoflurane, Desflurane, Sevoflurane, Nitric Oxide, Xenon
(Practical implementation limits the number of gases that can be measured to 8-10)

43
Q

*Magnetic Sector

A

Detection planes positioned for molecular species

Can simultaneously report multiple gases

44
Q

*Quadrapole

A

Four cylindrical rods
Ions are separated in a quadrupole based on the stability of their trajectories in the oscillating electric fields that are applied to the rods

I&M Final (5 decks)

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