Pulmonary Function Tests

Question 1

Volume vs. capacity

Answer 1

• volume is the smallest subunit

- capacity has at least two volumes (ex: all volumes and capacities together make up total lung capacity TLC)

Question 2

Tidal Volume (TV)

Answer 2

the amount of air inspired during normal, relaxed breathing

Question 3

Inspiratory reserve volume (IRV)

Answer 3

additional air that can be forcibly inhaled after the inspiration of a normal tidal volume.

Question 4

expiratory reserve volume (ERV)

Answer 4

additional air that can be forcibly exhaled after the expiration of a normal tidal volume.

Question 5

Residual volume (RV)

Answer 5

volume of air still remaining in the lungs after the expiratory reserve volume is exhaled.

Question 6

total lung capacity (TLC)

Answer 6

maximum amount of air that can fill the lungs (TLC = TV + IRV + ERV + RV).

Question 7

vital capacity (VC)

Answer 7

total amount of air that can be expired after fully inhaling (VC = TV + IRV + ERV)

Question 8

inspiratory capacity (IC)

Answer 8

maximum amount of air that can be inspired (IC = TV + IRV).

Question 9

functional residual capacity (FRC)

Answer 9

amount of air remaining in the lungs after a normal expiration (FRC = RV + ERV)

Question 10

Why FRC is so frequently used in pulmonary testing

Answer 10

• most reproducible of all lung volumes and capacities

- tends to be the most accurate

Question 11

Two opposing forces that determine changes in FRC

Answer 11

• two opposing elastic recoils are:
• the chest wall pulling out and the lung pulling in
• when these two forces equalize you stop at that volume

Question 12

Diseases like emphysema that reduce lung elastic recoil results in a ____ in the FRC

Answer 12

-rise (FRC increases)

Question 13

In diseases that increase the lung elastic recoil (interstitial lung diseases) the FRC will

Answer 13

-Fall

Question 14

In emphysema, which force is predominant–the lung or the chest wall? Consequences for FRC?

Answer 14

-Because elastic recoil is lost in emphysema and there is no change in chest wall recoil, the forces of the chest wall outweigh the lung forces and “pull” the FRC higher into the lung volume

Question 15

In infiltrative diseases which force is predominant?

Answer 15

-since elastic recoil increases, FRC “falls”

Question 16

Volume-pressure curve–x and y axis

Answer 16

• x axis: Translung pressure (cm H2O)

- y axis: Vital capacity (L)

Question 17

When lungs go from a normal size to a smaller size (bucket to cup) it is called obstructive or restrictive lung disease?

Answer 17

-Restrictive

Question 18

When lungs go from a bucket to a bottle, it is called?

Answer 18

-Obstructive

Question 19

Main problem in obstructive lung diseases

Answer 19

• Volume is NOT the issue

- it is the ability to empty the lung–determined by the degree of obstruction as measured by flow

Question 20

Hallmarks of obstructive and restrictive lung diseases

Answer 20

• Obstructive: reduced FLOW

- Restrictive: reduced VOLUME

Question 21

Examples of obstructive diseases vs restrictive lung diseases

Answer 21

Obstructive: COPD, Asthma, Bronchiectasis
Restrictive: Everything else (interstitial lung disease, pleural disease like effusions or pneumothorax, neuromuscular diseases and chest wall deformities, central brain problems, etc)

Question 22

More use of PFTs for obstructive or restrictive disease?

Answer 22

Obstructive

Question 23

How to measure whether there is obstruction or restriction?

Answer 23

• Spirometry–ask pt to blow as hard and as fast and as long as they can into a spirometer–measures how much air can be forcibly exhaled.
• called Forced Vital Capacity (FVC)
• Another calculation made of how much of the FVC is able to be exhaled in first second–called FEV in 1 sec

Question 24

Obstructive vs. restrictive disease in spirometry

Answer 24

• Obstructive–low FEV1 aka low FEV1/FVC ratio

- Restrictive–looks like a normal one but with less volume (shorter curve)

Question 25

How to approach spirogram

Answer 25

• First determine if obstruction is present
• Look at the FEV1/FVC ratio first–if that is normal, then there is no obstruction. If it is low, there is restriction
• If FEV1/FVC is low, there is obstruction

Question 26

Mixed disorders

Answer 26

• If FVC is normal, it is what? IF FVC is low as well, it is a pure obstruction
• If FVC is low as well, it is possible to have a mixed disorder but can’t tell it on spirometry alone
• Path of many obstructive lung diseases have low FCV as well

Question 27

A low FEV1/FVC will ALWAYS mean

Answer 27

• obstruction and will NEVER mean MIXED

- Mixed is ALWAYS wrong answer on the test!!

Question 28

Flow-volume loop–x and y axis; what does the flow volume loop measure?

Answer 28

• x-axis: vital capacity (volume in L)
• y-axis: speed (Flow)
• measures how fast air is moving when it passes that point of vital capacity
• line below the x axis is inspiration and the line above x axis is exhalation

Question 29

extra-thoracic obstruction

Answer 29

• pressure below the obstruction during exhalation is greater than atmospheric pressure above the obstruction so airflow during exhalation is unimpeded and normal
• BUT during inspiration, since the diaphragm descends, it creates intrathoracic pressure LESS than atmospheric pressure so the atmospheric pressure narrowing of the obstruction during inhalation

Question 30

Intra-thoracic airway obstruction

Answer 30

• Intraluminal pressure in the trachea in the thorax (confines of the pleural reflection) is greater above the intra-thoracic obstruction then below so now airflow is normal during inhalation
• BUT during exhalation, the intra-thoracic pressure becomes greater than intraluminal pressure and narrows the obstruction further limiting flow

Question 31

Dynamic hyperinflation

Answer 31

-In emphysema, the decreased expiratory time (bc of increased respiratory rate during exercise) results in more air-trapping and increases the FRC shifting the tidal-flow loop curve to the LEFT

Question 32

Tidal breathing at rest in pt with COPD

Answer 32

• intersects with patients maximal effort and the flow rates are LOWER than even for normal tidal volume breathing
• From energy standpoint, COPD pt uses maximal effort

Question 33

Diffusion Capacity (DLCO) measures

Answer 33

• effective alveolar-capillary blood volume
• interaction bw oxygen and hemoglobin occurs at alveolar-capillary level–large combined surface area
• Anything that reduces that area results in lower DLCO so it measures more than just simple diffusion of gas across membrane

Question 34

THE DLCO MEASURES WHAT??

WHAT ARE THE THREE MOST COMMON THINGS THAT CAN DECREASE DLCO??!

Answer 34

• DLCO measures the effective alveolar-capillary blood volume
• 1) emphysema, 2) pulmonary fibrosis/interstitial lung disease and 3) pulmonary vascular disease can reduce DLCO