1. PFT

2. Pulmonary Diagnostics
Performed by RT’s:
Pulmonary Function Tests
Arterial Blood Gases
Other:
V/Q scan
Radiological studies

3. Pulmonary Function Tests:
These are the four basic:
Lung Volumes & Capacities
Spirometry
FRC Determination
Diffusion Capacity

4. Lung Volumes & Capacities

5. Lung Volumes & Capacities
IRV: Inspiratory Reserve Volume
VT (VT): Tidal Volume
FRC: Expiratory Reserve Volume
RV: Residual Volume, can never be blown out!

6. Lung Volumes & Capacities
Lung Capacities:
IC: Inspiratory Capacity, Often done therapeutically
VC: Vital Capacity, the useable amount of air in the lungs
FRC: Functional Residual Capacity, the amount of air left in the lungs after a normal exhalation.
TLC: Total lung capacity.

7. Terms to know: BTPS ATPS ATPD
Q: What happens to air from BTPS to ATPS?
A: It cools from body temp to room air. The effects volume (Charles’ Law).

8. CL= Volume/pressure Vital Capacity
VC is decreased in restrictive component of disease.
Restrictive (among other things) is a disease of low compliance.
CL= Volume/pressure

9. Compliance Examples: 1000 ml / 20 cmH2O = 50 ml/cmH2O
Okay Compliance
800 ml /40 cmH2O = 20 ml/cmH2O
Bad compliance

10. Spirometry

11. Spirometry Definition
Spirometry is a Forced Expiratory Vital Capacity
Maximum effort in the first second is important.
The FVC is timed and graphed.
The values of importance in the test are…. (next slide)

12. Spirometry
FVC
To meet “ATS standards” one must blow out for 6 seconds or obvious plateau
No coughs or starts-and-stops
Good “start of test” (computer “back extrapolates” volume to tell)
Three efforts with at least two efforts being 200 ml apart.
Predicted value calculated from age, height, sex, race, weight.

13. GO!
Start
Normal Tidal breathing
Back to Normal breathing
FVC Tracing

14. FVC Tracing
FVC
FEV1
Volume (ml)
1 sec
Time (Sec)

15. FEV1 First major timing mark:
Measured in milliliters, (like FVC) represents the amount of air blown out in the first second of the FVC maneuver.
By itself, is non-specific since it is low in both obstructive and restrictive categories.

16. FEV1/FVC
The FEV1 divided by FVC is one of the most useful values in this diagnostic test.
This value compares the amount blown out in one second to the total FVC and expresses this as a percentage.
Generally, high percentages are good and low percentages are bad.

17. Example
FVC = 4.0 L
FEV1 = 3.8 L
3.8
= 95%
4.0
Is this good or bad?

18. FEF25-75% This value indicates flow in the small airways.
Is derived by taking the slope of the line created by plotting 25% and 75% of actual FVC.
This is the most sensitive indicator of mild or early obstructive component.

19. { { { { { FEF 25-75% 100% 75% 50% 25% Slope = Y2-Y1 X2-X1 75% FVC
We will not calculate this, or do this measurement manually, but it is nice to know how this value is derived.
50% {
25% FVC
25%

20. Peak Expiratory Flow Rate
PEFR roughly indicates flow in the large airways.
Easy to perform, and therefore a common diagnostic test to indicate airway obstruction.
Calculated (or derived) much like the FEF25-75%

21. Others
FEF
FEV2
FEV3

22. Classification of spirometry based on disease process

23. Classification Normal
Early small airways disease (obstructive component)
Obstructive
Restrictive
Combined

24. Obstructive Diseases Chronic Bronchitis Asthma Emphysema
Combined Obstructive/Restrictive:
Cystic Fibrosis (combined)
Bronchiectasis (combined)

25. Restrictive (Wide category!)
Acute Restrictive component
Infectious diseases such as pneumonia
Non-infectious disease processes such as pulmonary edema
Chronic Restrictive component
Infectious diseases such as fungal diseases
Environmental diseases such as Asbestosis

26. Obstructive Spirometric classification
Normal volumes
FVC
Reduced flows
FEV1/FVC
FEF25-75%
FVC = 3.7
1.2 / 3.7 = 32%
FEV1 = 1.2
1 sec

27. Percent of Predicted Actual / Predicted = % of Predicted Example:
Based on my age, height, sex, race, and weight, I am predicted to have a Forced Vital Capacity of 4.7 Liters. I performed the test and only scored 3.6 L. What is my “percent of predicted”, and is this normal?

28. Percent of Predicted
Although most people perform more than 82% of predicted, we call an FVC percent of predicted “abnormal” when it falls below 75%

29. Obstructive Spirometric classification
Normal volumes
FVC
Reduced flows
FEV1/FVC
FEF25-75%
FEF25-75%= 3.5 L/s
FEF25-75%= 1.0 L/s
75% = 2.8
Notice the difference in slope for the obstructive (black) vs. the normal (green)
25% = .93
1 sec

30. Restrictive Spirometric classification
Low Volumes
Normal “flows”
FEV1/FVC
FEF25-75%
1.9 / 2.0 = 95%
FVC = 2.0
FEV1 = 1.9

31. Also….
FEV1
FEF25-75%
PEFR
Can be compared to predicted normals and scored as “percent of predicted”

32. Flow Volume Loop

33. Flow volume loop
We have been graphing spirometric data on Volume / Time scale, but you can also graph the data on Flow / Volume scale…

35. Discussion What is the difference between SVC and FVC
Why does obstructive disease manifest itself as low flows on the expiratory curve.
Why doesn’t restrictive disease affect flows?

36. Next time….
Diffusion Capacity
FRC Determination