Pulmonary Function Testing

Question 1

Indications for pulmonary function testing

Answer 1

Evaluate signs/symptoms of lung disease

Assess progression of lung disease

Monitor effectiveness of therapy

Evaluate pre-op patients in selected situations

Screen those at risk of pulmonary disease (smokers, occupational exposures)

Monitor for potentially toxic effects of certain drugs or chemicals (e.g., amiodarone, beryllium)

Question 2

Contraindications to pulmonary function testing

Answer 2

Not generally indicated in pts without symptoms

May be confusing when non-pulmonary diseases that affect pulmonary system are active (e.g., CHF)

Question 3

Component of pulmonary function testing that results in measurement of air movement into and out of the lungs using respiratory maneuvers, determining how much air can be inhaled and exhaled, and how fast

Answer 3

Spirometry

Question 4

3 most important measures of spirometry

Answer 4

Forced vital capacity (FVC)

Forced expiratory volume in 1 second (FEV1)

FEV1/FVC ratio

Question 5

Describe respiratory maneuvers used for spirometry

Answer 5

Pt inhales as deeply as possible, then exhales as long and as forcefully as possible — the amount exhaled is the FVC. The amount of air exhaled during the first second of the FVC maneuver is the FEV1

Question 6

What effect might asthma or emphysema have on the FEV1?

Answer 6

Decrease it (these are obstructive diseases)

Question 7

Why might spirometry be repeated?

Answer 7

To check for reproducibility (usually performed 3x)

After giving bronchodilator to check for significant response

Question 8

Diffusing capacity is another component of PFTs. It is the measure of the ability of the lungs to transfer gas and is most efficient when surface area for gas transfer is high and blood is readily available to accept gas being transferred. What compound is typically used to measure diffusing capacity?

Answer 8

Carbon monoxide, because it is more soluble in blood than lung tissue, and the amount entering the blood is limited by the lungs ability to transfer it (i.e., it binds avidly to Hb)

Question 9

In what conditions might diffusing capacity be decreased?

Answer 9

Conditions that minimize ability of blood to accept and bind diffusing gas (e.g., anemia)

Conditions that decrease the surface area of alveolar-capillary membrane (e.g., emphysema, PE)

Conditions that alter membrane’s permeability or increase its thickness (e.g., pulmonary fibrosis)

Question 10

What 2 measurements in pulmonary function testing cannot be determined by spirometry?

Answer 10

Residual volume (RV)
Total lung capacity (TLC)

Question 11

What are 2 ways in which to measure RV and thus TLC? [TLC = RV + FVC]

Answer 11

Pt breathes in inert gas like helium, then concentration of helium is measured in expired air. This measurement is used to calculate RV

Pt sits in airtight booth in which pressure is measured as pt breathes

Question 12

RV and TLC measurements can be used to add information gained from spirometry. How are these measurements useful in obstructive vs. restrictive disease?

Answer 12

Obstructive: measurement of RV and TLC can demonstrate air trapping and hyperinflation

Restrictive: the TLC is needed to confirm true restriction and better quantitate the degree of restriction

Question 13

Describe changes (or lack thereof) in FVC, FEV1, FEV1/FVC ratio, and TLC in pt with obstructive disease

Answer 13

FVC decreased or normal

FEV1 decreased

FEV1/FVC decreased

TLC normal or increased

[note that diffusing capacity is typically decreased d/t decreased surface area needed for gas exchange]

Question 14

To quantify the degree of obstruction, the clinician needs to note the pt’s _____ as a percentage of predicted value

Answer 14

FEV1

Question 15

Describe changes (or lack thereof) in FVC, FEV1, FEV1/FVC ratio, and TLC in pt with restrictive disease

Answer 15

FVC decreased

FEV1 decreased or normal

FEV1/FVC normal

TLC decreased

[note that diffusing capacity is often decreased d/t altered membrane permeability]

Question 16

To quantify degree of restriction, one should note either the pt’s _____ or ____ as a percentage of the respective predicted value

Answer 16

FVC; TLC

Question 17

Once you have identified that a pt has an obstructive pattern on PFTs, if you note that they also have a low FVC, 2 possibilities exist — what are they?

Answer 17

1. Mixed pattern with both obstructive and restrictive components (this is the case if TLC is also decreased)
2. Obstruction is very severe and has lead to significant air trapping (this is the case if TLC is normal or increased, and RV is increased)

Question 18

Restrictive patterns seen on PFT may be due to causes inside or outside the lung parenchyma. What is an example of a pulmonary parenchymal cause of a restrictive pattern?

Answer 18

Pulmonary fibrosis

Question 19

Restrictive patterns seen on PFT may be due to causes inside or outside the lung parenchyma. What are some extraparenchymal causes of a restrictive pattern?

Answer 19

Obesity
Neuromuscular diseases
Chest wall deformities
Large pleural effusions

Question 20

Restrictive patterns seen on PFT may be due to causes inside or outside the lung parenchyma. How can you distinguish between pulmonary parenchymal causes and extraparenchymal causes?

Answer 20

Distinguish based on diffusing capacity of the lung (DLCO)

If DLCO is still below normal after being adjusted for lung volume, Hb level, or both, then parenchymal disease is likely.

If DLCO is normal after adjustment, it suggests that the cause is extraparenchymal

Question 21

Bronchoconstricting agent that is administered to confirm the diagnosis of suspected asthma when PFTs have failed to establish diagnosis

Answer 21

Methacholine

[i.e., methacholine challenge test; also usefuly in evaluating occupational asthma]

Question 22

Is hypersensitivity pneumonitis typically characterized as an obstructive or restrictive pattern on PFTs?

Answer 22

Restrictive

Question 23

Is alpha 1 antitrypsin deficiency typically characterized as an obstructive or restrictive pattern on PFTs?

Answer 23

Obstructive

Question 24

In a patient with alpha-1 antitrypsin deficiency, why would you expect their DLCO to be markedly decreased on PFTs?

Answer 24

Neutrophil elastase is an enzyme that breaks down tissue/alveoli in the lung, when unopposed due to deficiency in alpha-1 antitrypsin, there is excessive destruction resulting in decreased surface area for gas exchange

[DLCO = diffusing capacity of the lung]

Question 25

A patient presents c/o dyspnea on exertion. Pulmonary function testing reveals that the FVC, FEV1/FVC ratio, and total lung capacity are all normal. However, the DLVA (DLCO adjusted for volume) is significantly reduced. What conditions might present this way?

Answer 25

Anemia
Pulmonary HTN
Chronic thromboembolic disease