Ch. 3 Flashcards
What is TLC?
volume of gas that remains in the lungs after maximal inspiration
What is TLC used for?
To diagnose restriction, air trapping, and hyperinflation
What is RV?
The amount of gas that remains in the lungs at the end of maximal expiration
What is FRC?
Volume of gas remaining in the lungs after maximal breath
What’s the formula for FRC?
FRC = ERV+RV
What is the RV/TLC fraction? What must it be expressed as?
Amount of TLC that cannot be exhaled; a percentage
What does an inc. in the RV/TLC fraction indicate?
Hyperinflation or air trapping
The RV cannot be measured _______?
Directly
What are the 3 methods used for RV?
• helium dilution
• nitrogen washout
• body box
What is the He dilution method?
• Closed circuit system
• Measures 10% of helium
• Source of O2
• Volume based spirometer
• He analyzer (must be calibrated)
• CO2 & H2O absorber
What does He dilution measure?
FRC and estimates lung volumes
The helium is _______ until _______ is reached?
Diluted; equilibrium
Helium ______Vt & TLC
Underestimates
What is the nitrogen washout?
• open circuit system
• Pneumotachometer
• nitrogen analyzers & 100% O2
• pt is given 100% O2
• pt continues to rebreathe 100% O2
What does an inc in N2 mean?
You have leak
What does the N2 washout measure?
Flow rate of gases during breathing
How long must you wait before you can retest for N2 washout?
15 min
How long does the test take in healthy lungs?
3-4 (up to 7-8) mins
What does the body box measure?
• FRC & thoracic gas volume
• Gas in thorax
What is the body box based on?
Boyle’s law
What is Boyle’s law?
A volume of gas varies inversely w/pressure when temp is constant
What are the 2 types of body boxes?
• flow based
• constant volume (pressure type)
Changes in _______ pressure is measured at the _____ when shutter is closed?
Alveolar; mouth
Test must be _____ & ______ .
Acceptable; replicable
What are some examples of drift or artifact?
Cough or leaks
How do you know if calibration is done correctly?
Tracing will go off
What is the frequency for acceptable tests?
0.5-1
How many test do you need within acceptable parameters?
3
FRC must be within _____ %
15
What is the most accurate test for measuring lung volumes?
Body box
____ can also be monitored?
Raw
Body box shows what?
Instant changes throughout testing
Measurements are not affected by _____ effort?
Pt
Comparing the FRC is optimal for assessing ______ _______ ?
Air trapping
Single breath He dilution is?
• closed circuit
• calculated as part of DLCO
What does Single breath He dilution measure?
TLC
Single breath N2 washout is?
An open circuit
What are the 4 phases of volume for N2 washout?
• lung volumes
• closing capacity
• closing volumes
• anatomic dead space (gas that does not participate in gas exchange).
How many phases are there of the N2 washout curve?
Phase 1
Phase 2
Phase 3
Phase 4
What is phase 1 of the N2 washout curve?
Upper airway gas from the anatomic dead space (V danat) consisting of 100% O2
What is phase 2 of N2 washout?
Mixed dead space gas in which the relative concentration of O2 and N2 change abruptly as the V danat volume is expired
What is phase 3 of N2 washout?
A plateau caused by the exhalation of alveolar gas in which relative O2 and N2 concentrations change slowly and evenly.
What is phase 4 of the N2 washout?
An abrupt increase in the concentration of N2 that continues until RV is reached
An increase in the stage of phase 3 indicates what?
Uneven distribution
Deceased TLC =
Suspected restriction
Increased TLC =
Suspected obstruction
Increased FRC =
Suspected hyperinflation or air trapping
Increased RV w/ normal TLC =
Air trapping
Increased RV w/ inc.TLC =
Hyperinflation
Inc. RV w/normal TLC & Inc RV w/ inc. TLC are indicators of what?
Obstruction
⬇️ FRC, RV, & TLC are all indicators of what?
Restriction
What makes up IC?
IC=IRV+Vt
What make up VC?
VC=IRV+Vt+ERV
What is the TLC made up of?
TLC = IRC+VC+Vt+FRC+ERV+RV+IC
Everything
Label this pic
- IRV
- VC
- Vt
- FRC
- ERV
- RV
- IC
- VC
- ERV
- RV
- FRC
- Vt
- IRV
- TLC
