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RTH 217 > MVV - Maximum Voluntary Ventilation > Flashcards

MVV - Maximum Voluntary Ventilation Flashcards

1
Q

What is the definition of MVV?

A

the largest tidal volume and rate that can be breathed per minute by voluntary effort

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2
Q

How is a MVV test performed?

A
  • patient is told to breathe in and out as fast as possible until told to stop
  • performed for 12-15 seconds
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3
Q

What does MVV measure?

A

the muscular mechanics of breathing

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4
Q

What does it mean if a patient has a decreased MVV?

A
  • obstructive disease (increased Raw)
  • muscle weakness
  • decreased compliance
  • poor patient effort
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5
Q

What does predicated normal values mean?

A

all values are compared with the predicted normal values for that individual

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6
Q

How are predicted normal values expressed?

A

as percents. actual value / predicted value = % of predicted

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7
Q

What are predicted normal values primarily based on?

A
  • age
  • height
  • sex
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8
Q

What is the predicted percent range for a normal PFT?

A

80-100

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9
Q

What is the predicted percent range for a mild disorder PFT?

A

60-79

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10
Q

What is the predicted percent range for a moderate disorder PFT?

A

40-59

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11
Q

What is the predicted percent range for a severe disorder PFT?

A

<40

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12
Q

What does it mean if a patient has a volume measurement (FVC) that is decreased (i.e. 65% of predicted)?

A

there is a mild restrictive problem

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13
Q

What does it mean if a patient has a flow measurement that is 83% of predicted?

A

there is no obstructive problem

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14
Q

What does it mean if a patient has a volume measurement that 80+% of predicted?

A

there is no restrictive problem

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15
Q

What does it mean if a patient has a flow measurement that is 44% of predicted?

A

there is a moderate obstructive problem

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16
Q

What He dilution?

A
  • closed method

- initially no He in patient’s lungs. give patient a known % of He dilution. change in He% is used to determine FRC

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17
Q

How long should a Helium dilution procedure last for both healthy and small patients?

A

~2-5 minutes

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18
Q

Helium concentration on system stabilizes and does not fluctuate more than ___ during a ___ period

A

.02; 30 seconds

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19
Q

What criteria would cause you to stop a helium dilution procedure if it is not yet finished?

A
  • system leak

- patient unable to continue

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20
Q

What is nitrogen washout?

A
  • open method
  • the FRC is washed our of the lung by having patient inspire 100% O2
  • the FRC goes into a collecting spirometer and is measured to calculate it
21
Q

How long should a nitrogen washout take in normal lungs?

A

~2-5 minutes

22
Q

What does a nitrogen washout time of 7 minutes indicate?

A

poor distribution

23
Q

What should you make sure you do before performing a nitrogen washout?

A

discontinue supplemental O2

24
Q

How does a leak affect the FRC in both helium and nitrogen tests?

A
  • FRC is artificially raised

- equilibration may not occur

25
Q

What is the plethysmopgraph/body box?

A
  • aka thoracic gas volume (TGV) or BP

- uses boyle’s law to determine TGV (P1V1 = P2V2)

26
Q

What does the plethysmopgraph/body box do?

A

measures gases trapped and otherwise excluded from the FRC with the other procedures

27
Q

In healthy subjects, TGV ___ FRC

A

equals

28
Q

How is a BP test performed?

A
  • patient performs open-glottis panting 1-2 breaths per second
  • shutter is suddenly closed at end-expiration
  • panting continues against a closed shutter
  • airflow is not possible against a closed shutter
29
Q

Airflow is not possible against a closed shutter, thus mouth airway pressure ___ alveolar pressure

A

equals

30
Q

How is airway resistance measured?

A

measure the changes in pressure vs flow in the body box

31
Q

What is normal airway resistance?

A

0.6-2.8 cmH2O/L/sec

32
Q

How is compliance determined?

A

by volume change per unit pressure change (60-100 ml/cmH2O)

33
Q

What two primary parameters are used for calibration of the body box?

A
  • pressure verified with a mercury or water manometer

- flows verified with a rotameter

34
Q

What are the advantages of the body box?

A
  • TGV not affected by lung ventilation
  • quicker test
  • easily repeatable
35
Q

What are the disadvantages of the body box?

A
  • patient may be unable to enter box due to physical limitations
  • claustraphobia prohibits patient from entering box
  • patient may be unable to pant acceptably
36
Q

What must specific things are calibrated during your calibration of the BP?

A
  • mouth pressure transducer
  • flow transducer
  • cabinet pressure transducer
37
Q

What is the purpose of a gas analyzer?

A
  • determine FRC

- measures DLCO

38
Q

What are the methods of calibration?

A
  • utilize known gas value
  • mechanical lung analog
  • test known subjects
39
Q

What is the known gas values calibration method?

A
  • utilizes different precise gas values
  • high concentration of gas source
  • high concentration diluted with room air (accuracy, linearity)
40
Q

What is the mechanical lung analog method?

A

calibrated syringe with known constant and known variable lung volumes

41
Q

What is biological testing?

A
  • calibration by using a person who gets similar lung volumes each time
  • pretty common component of quality control
42
Q

What are the two names of oxygen analyzers?

A
  • galvanic (fuel cell)

- polarographic (clark electrode)

43
Q

What is the name of the helium analyzer?

A

wheatstone bridge (thermal conductivity)

44
Q

What is the name of the nitrogen analyzer?

A

geisler tube ionizer

45
Q

What is a mass spectrometer used for and what does it measure?

A
  • stress testing

- He, N2, O2, CO2

46
Q

What is chromatograph or infrared absorption use for and what does it measure?

A
  • DLCO testing

- Ne, O2, N2, CO

47
Q

How are gas analyzers calibrated to “zero?”

A

by running a gas through it that is free of that particular gas (i.e. 100% O2 would read 0% on an He or N2 analyzer)

48
Q

What is a known concentration of a gas used to do during calibration?

A

set the second or third point of calibration

RTH 217 (6 decks)

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