PFT - Definitions

Question 1

Inspiratory Reserve Volume (IRV)

Define. How is it obtained?

Answer 1

How much volume can be inhaled beyond normal breathing; A subdivision of vital capacity.

Measured from a slow, non-forced, non rapid effort. Value from Inhale peak of Vt minus Inhale peak of max inhaled breath.

Question 2

Tidal Volume (VT)
Define. How is it obtained?

Answer 2

The volume of gas moved in and out of lung with each breath

Measured from peak inspiration to peak exhalation with normal breathing

Question 3

Expiratory Reserve Volume (ERV)

Define. How is it obtained?

Answer 3

Largest volume of gas that can be expired from the resting end-expiratory level; a subdivision of volume capacity

Measured from peak of expired Vt to exhale peak of max exhaled breath

Question 4

Residual Volume (RV)
Define. How is it obtained?

Answer 4

The volume of gas remaining in the lungs at the end of a maximal expiration. Dead space.

Is a calculated value: ?

Question 5

Vital Capacity (VC)
Define. How is it obtained?

Answer 5

The largest amount of air that can be forced from the lungs after maximum inhalation

Measured from peak max inspiration to peak max exhalation.
VC = IRV+VT+ERV

Question 6

Total Lung Capacity (TLC)

Define. How is it obtained?

Answer 6

The volume of gas contained in the lungs after maximal inspiration

Is a calculated value:
TLC = VC+RV

Question 7

Inspiratory Capacity (IC)
Define. How is it obtained?

Answer 7

The largest volume of gas that can be inspired from the resting expiratory level; a subdivision of volume capacity

Measured from normal (Vt) exhaled peak to maximal inhaled peak

IC = IRV+VT

Question 8

Functional Residual Capacity (FRC)

Define. How is it obtained?

Answer 8

The volume of gas remaining in the lungs at the end of a quiet breath

Is a calculated value:
FRC = ERV + RV

Question 9

Obstructed lung

What happens to volumes and capacities compared to normal lung?

Answer 9

Decrease in IRV, VC, IC, ERV
Increase in VT, TLC, RV, FRC

More difficult to move gas out when obstructed because airways shorten and narrow on exhalation. This means more gas will be trapped in the lungs, increasing the RV. If RV increases then less volume can be moved in on the next breath, therefore, IRV (proportional to VC, IC) decreases. ERV also decreases because less air to move out.

Increase WOB is required therefore VT (proportional to TLC and FRC) increase.

Question 10

Restricted Lung

What happens to volumes and capacities compared to normal lung?

Answer 10

IRV, VT, VC, IC, TLC, ERV, RV,FRC all decrease.

WHY????

Question 11

ATPS

Answer 11

Ambient Temperature and Pressure Saturated
T = 20C
Pbar = 760mmHg
Water saturation at 20C = 17mmHg

Question 12

BRPS

Answer 12

Body Temperature and Pressure Saturated
T = 37C
Pbar = 760mmHg
Wather saturation at 37C = 47mmHg

Question 13

STPD

Answer 13

Standard Temperature and Pressure Dry
T = 0C
Pbar = 760mmHg
Dry (not water saturation)

Question 14

When would STPD be used in PFT?

Answer 14

1) Diffusion capacity testing

2) Values representing cellular metabolism (exercise testing)

Question 15

What would happen to the volume recorded by the spirometer during spirometry if the value was not converted to BTPS?

Answer 15

Values would be recorded in ATPS and would appear to be lower than they actually are in BTPS.

Question 16

What factors should be considered in predicted values? Why do we need to enter these values before testing?

Answer 16

Height
Age
Sex
Ethnicity

These factors must be entered so the correct predicted values are displayed. Failure to do so may result in false abnormalities.

Question 17

What is the purpose of the nose clip? Why is it important to remember the nose clip if inspiratory portion is measured.

Answer 17

Prevents air from escaping though the nose, ensuring accurate measurements are being recorded.

Important during the inpiratory portion because…

Question 18

Why do we prefer sitting over standing during testing? Will the measured volumes differ?

Answer 18

Pt is more stable seated. If they become light headed or faint they are less likely to injury themselves. The measured volumes are comparable, therefore either method is acceptable.