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CPFT/RPFT Review > Lung Testing > Flashcards

Lung Testing Flashcards

(92 cards)

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1
Q

Typical TLC

A

6L

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2
Q

Typical RV

A

1.2L

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3
Q

Typical FRC

A

2.4L

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4
Q

Typical TGV

A

2.4L

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5
Q

Typical RV/TLC

A

20%

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6
Q

Methods for measuring static lung volumes

A

Helium dilution
Nitrogen washout
Body plethysmography
Radiological exam

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7
Q

Define: Helium dilution

A

Uses helium in a closed system to measure FRC

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8
Q

Procedure for Helium dilution test

A

-Patient rebreathes 10% helium and air at FRC
-The He is distributed throughout the lungs until equilibrium is achieved
-Oxygen is slowly added to maintain baseline volume
-Initial and final He concentrations are measured and used to measure FRC

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9
Q

He dilution- causes for unusually high results

A

Leak, ruptured eardrum, improper switch in, or analyzer failure

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10
Q

Nitrogen washout times

A

Normal= 3 min or less
Obstructive= 3-7+ min

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11
Q

Max He dilution or N2 washout time

A

7 minutes

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12
Q

Explain Nitrogen washout test

A

-Uses 100% O2 in an open circuit and does not require a CO2 scrubber
-Pt breathes 100% O2 at FRC until the exhaled N2 concentration is <1.5%
-Collected N2 is used to calculate FRC

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13
Q

Troubleshooting N2 washout

A

Random spike = analyzer failure due to N2 in exhaled moisture
Increase in N2 or failure to decrease = leak

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14
Q

Body box pressure graph

A

Vertical axis = mouth pressure
Horizontal axis = box pressure
Vertical only = no box pressure signal
Horizontal only = no mouth pressure signal

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15
Q

Hysteresis with plethysmography

A

Panting loops are too open due to breathing too hard or fast

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16
Q

Lung volumes via CXR

A

AP & lateral CXR taken and divided into zones
Geometric formulas are used to measure TLC
Very accurate but rarely used

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17
Q

Medication withholding times for bronchoprovocation testing

A

SABA= 6 hours
SAMA= 12 hours
LABA= 24 hours

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18
Q

Purpose of Exercise Challenge Testing

A

Assess airway hyperreactivity when heat and moisture are lost from airways during exercise

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19
Q

Purpose of Eucapnic Voluntary Hyperventilation Test (EVH)

A

Assess airway hyperreactivity by having the patient breathe at a high rate of ventilation to remove heat and moisture from the airways

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20
Q

Explain the purpose of the Mannitol Challenge Test (MCT, Aridol)

A

Mannitol indirectly stimulates the release of mediators that act on bronchial smooth muscle

MCT is very sensitive for asthma and may be used to monitor disease activity and anti-inflammatory therapy

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21
Q

Define: Airway Resistance

A

The difference in pressure between the mouth and alveoli, related to gas flow at the mouth

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22
Q

Typical airway resistance values

A

0.6 - 2.4 CWP/L/sec

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23
Q

Specific Airway Resistance

A

Airway resistance measured at a known volume
Measured in CWP/L

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24
Q

Normal airway resistance divisions

A

Nose, mouth and upper airway= 50%
Trachea and bronchi= 30%
Small airways= 20%

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25
Airway resistance changes in mild obstructive disease
Very little change because disease is mostly in small airways
26
Airway resistance loops - hysteresis is caused by…
Panting frequency too low or volume too high
27
Define: Airway Conductance (Gaw)
Flow per unit of pressure change Reported in L/sec/CWP
28
Normal airway conductance
0.4 - 1.7 L/sec/CWP
29
Define: Airway Compliance
Volume change per unit of pressure change Clt = compliance of the lungs and thorax Cl = compliance of the lungs Ct= compliance of the thorax
30
Purpose of Esophageal Balloon Technique
Used to measure static lung compliance alone
31
Define: maximum elastic recoil pressure
The greatest negative pressure attained at TLC
32
Normal esophageal balloon pressure at FRC
-5cwp
33
Calculating static compliance
Cst = change in volume / change in static pressure (L/cwp)
34
Define: Coefficient of Retraction
The max static recoil pressure of the lung relative to TLC
35
Normal static compliance
Lung = 0.2 L/cwp Thorax = 0.2 L/cwp Lung + thorax = 0.1 L/cwp
36
Normal coefficient of retraction
4 - 8 cwp/L
37
Normal max static recoil pressure
25 - 35cwp
38
Typical MIP
-60cwp
39
Typical MEP
80-100cwp
40
Normal DLCO
25 mL/min/mmHg STPD
41
STPD
Standard temperature and pressure dry Standard temp= 0 Celsius Standard pressure= 760mmHg
42
What happens to DLCO measured at BTPS and corrected to STPD
Value should decrease
43
Factors that affect DLCO
Hb PACO2 COHb Pulmonary capillary blood volume Body position Altitude BHT Washout volume Alveolar sample size
44
Effect of exercise on DLCO
DLCO will increase 2-3x during exercise
45
Effect of mouth leak on DLCO
Increased DLCO due to loss of CO gas
46
Normal DLCO gas mixtures
0.3% CO, 10% He or 0.3% CH4, 21% O2, balance N2
47
Normal CO concentration in room air
0.03%
48
Explain: DLCO steady state
Patient breaths 0.1-0.2% CO mixed with air for 5-6 minutes until steady state is reached DLCO SS1 (Filey method) can be used for exercise testing Requires an ABG (ETCO2 and PACO2 are required)
49
DLCO rebreathing (DLCO RB) requires a…
CO2 scrubber
50
DLCO intrabreath
DLCO IB Patient inhales DLCO gas mixture (CO, CH4, O2, air) to TLC DLCO is measured rapidly during a slow and complete exhalation from TLC to RV Can be used for exercise testing
51
Define: Membrane Diffusion Coefficient Factor (Dm)
Calculation of the resistance caused by the A/C membrane
52
Equipment required for He dilution test
CO2 scrubber, desiccant and He analyzer
53
If He dilution test is continued after equilibrium…
The He volume will begin to increase as O2 and CO2 are consumed
54
End of He dilution test
He concentration changes <0.02% over 30 seconds
55
He dilution- failure to reach equilibrium
Leak
56
He dilution- unusually slow equilibrium time
Check blower speed
57
He dilution- Increasing RR or Vt
CO2 scrubber exhausted
58
He dilution- dizziness or visual changes
Hypoxemia
59
During He dilution test, saturated expired air passing through desiccant will result in volume loss of approximately…
5%
60
Exercise challenge test procedure
Exercise to increase HR to 80-90% of predicted max for 6-8 minutes FVC immediately after and every 5 minutes until FEV1 drops then begins to return to normal
61
Positive ECT, EVH or mannitol challenge test
Drop in FEV1 > 15% from baseline
62
Calculation for airway resistance
(Mouth pressure - alveolar pressure) / Flow
63
Airway resistance changes in large airway obstructions
Significantly increased Raw and increased WOB
64
Airway resistance changes in acute asthma attack
Raw may increase up to 3x
65
Airway resistance changes in advanced COPD
Raw may increase because large airways are involved
66
Airway resistance loops - small
Panting frequency too high or volume too low
67
Airway resistance loops - top of loop widens
High inspiratory resistance
68
Airway resistance loops - bottom of loop widens
High expiratory resistance
69
Airway resistance loops - loops turn more vertical
High inspiratory and expiratory resistance
70
Airway resistance loops - normal loops but wide
Overall increased resistance (i.e. asthma)
71
Benefit of measuring airway conductance
Determine effectiveness of bronchodilator therapy in uncooperative patients May be more sensitive than Raw detecting small airway disease
72
Relationship of Raw to Gaw
Gaw is the reciprocal of Raw (Raw of 2 becomes Gaw of 1/2)
73
Optimal placement for esophageal balloon
Tip 35-45cm from the nose
74
Measuring static lung compliance from esophageal balloon technique
Lung compliance is the slope of the pressure-volume curve from FRC to FRC+0.5L
75
Esophageal balloon technique procedure
1. A catheter (marked at 50cm) with a small balloon is inserted into the esophagus 2. Balloon deflated then reinflated with exactly 0.5mL air before each measurement 3. Patient inspires to TLC to standardize the lung volume 4. Patient inspires again and pressure and volume are measured at several points with zero flow
76
Calculation for coefficient of retraction
Static pressure at TLC divided by volume
77
Effect of PACO2 on DLCO
Increased PACO2 will increase DLCO due to reduced PAO2 and reduced competition for binding with Hb
78
Effect of COHb on DLCO
Increased COHb will decrease DLCO due to back pressure
79
Effect of supine body position on DLCO
Supine position will increase DLCO due to increased blood flow
80
Effect of increased altitude on DLCO
Increased altitude will increase DLCO due to decreased PAO2
81
Effect of restrictive lung disease on DLCO
DLCO will decrease in patients with RLD and reduced lung volume
82
Effect of COPD on DLCO
DLCO will decrease with COPD due to loss of surface area, V/Q mismatch and increased distance from the terminal bronchioles to the A/C membrane
83
Effect of air dilution in DLCO sample volume
If air dilutes the exhaled gas from DLCO SB, both the calculated DLCO and VA values with be erroneously high
84
Effect of polycythemia on DLCO
Polycythemia may increase DLCO above 100% predicted value
85
Membrane diffusion coefficient factor procedure
DLCO SB is performed at two different levels of O2 to determine the Hb reaction rate Back extrapolation to 0% O2 will reveal the resistance of the A/C membrane
86
Calculation for FRC from He dilution
(He 1 - He 2)/He 2 x Initial vol
87
Reporting He dilution results
Report the average of 3 acceptable efforts
88
Reporting N2 washout results…
Report the average of 2 efforts that agree within 10%
89
Positive methacholine test via Sgaw
Drop 35% from baseline
90
Mixing methacholine
Add 6.25mL NS to starting concentration, then… -For 5 doses, add 3mL progressively -For 10 doses, add 9mL progressively
91
Normal static lung pressure at FRC
-5cwp
92
Normal static lung pressure at TLC
-30cwp

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