Lecture 30 - Pulmonary Function Test

Question 1

What is flow rate?

Answer 1

Volume of air moved over time

Question 2

What is a forced exhalation test?

Answer 2

Measure of flow rate during a maximal expiration

Question 3

What is the forced expiratory volume? Notation? What kind of measure is this?

Answer 3

Volume of air exhaled in the first second of maximal expiration maneuver = FEV1

Measure of flow

Question 4

What is the forced vital capacity? Notation?

Answer 4

Total volume of air exhaled during a forced expiration = FVC

Question 5

What % of the FVC does the FEV1 comprise in a normal healthy individual? What will affect this normal number?

Answer 5

FEV1/FVC = 75-80% (or within 10% of the normal expected number)

Factors affecting this number: age, height, race, and gender

Question 6

What does it mean if the FEV1/FVC ratio is lower than within 10% of the standard value for a particular patient?

Answer 6

Airway obstruction, like with asthma and COPD

Question 7

FEV1/FVC ratio in restrictive respiratory diseases?

Answer 7

May reach 100% because they have a smaller volume to exhale due to bad compliance

Question 8

Is the FEV1/FVC ratio used to gage obstructive or restrictive lung diseases?

Answer 8

Obstructive ones

Question 9

Once obstruction is diagnosed through a forced exhalation test, how is severity determined?

Answer 9

Based on absolute FEV1 ONLY and its % of predicted normal:

Physiological variant > mild > moderate > moderate severe > severe > very severe

Question 10

What is going on if the FEV1/FVC ratio is less than 10% of predicted normal, but the FEV1 alone is normal?

Answer 10

Physiologic variant: the FVC is much larger than normal (usually in great athletes)

Question 11

What is representative of a restrictive lung disease?

Answer 11

TLC < 80% of predicted normal through a full pulmonary test

Question 12

Once an obstructive lung disease has been diagnosed with a forced exhalation test, how can asthma and COPD be distinguished? What to note?

Answer 12

If issue with diffusion: emphysema (COPD)

If not issue then it’s either asthma or chronic bronchitis:

Asthma will show reversibility with an improvement of the FEV1 OR FVC by 12% (at least 200 cc*) with the use of bronchodilators

*this stipulation is necessary because in patients with emphysema have very very low FVCs so could have a 12% improvement that accounts for less than 200 cc

Question 13

What does a full pulmonary test involve?

Answer 13

1. Spirometry + tests for RV
2. Forced exhalation test
3. DLCO (diffusion capacity of the lungs for CO)

Question 14

What can be said about the DLCO?

Answer 14

Sensitive test, but not specific

Question 15

If there is decreased diffusion measured through the DLCO, what are potential causes?

Answer 15

1. Decrease in surface area:
   - Emphysema
   - Pulmonary embolism
   - Lung resection
2. Increased thickness of alveolar membrane:
   - Interstitial lung disease (group of diseases that includes sarcoidosis)
   - Pulmonary fibrosis
   - Pulmonary hypertension
   - Pneumonia
3. Anemia

Question 16

What is the lung parenchyma?

Answer 16

Respiratory zone

Question 17

Can you get patients with both COPD (emphysema + chronic bronchitis) AND asthma?

Answer 17

YUP

Question 18

Since asthma is not a chronic disease, it may be missed on a forced exhalation test on a good day. What can be done to fix this? What patients is this done on?

Answer 18

Done on patients in which asthma is suspected but with normal pulmonary function tests

Bronchoprovocation: induced bronchoconstriction using methacholine inhalation, cold air, or exercise => start with a tiny bit until the FEV1 starts declining or until top dose

If the FEV1 declines by 20% => positive test for asthma, if not 95% sure they do not have asthma

Question 19

What is the PC20? What does it mean?

Answer 19

Provocative challenge 20 = dose of methacholine causing a decline in FEV1 by 20% in asthma patients during a bronchoprovocation

• High: controlled mild asthma
• Low: severe asthma

Question 20

What does a normal PFT look like?

Answer 20

1. Top: age, race, height, gender to compare all normals on the sheet
2. Forced expiratory test with FEV1 + FVC + FEV1/FVC ratio + peak expiratory flow
3. Spirometry with 4 capacities + 4 volumes
4. Diffusion measures: DLCO
5. Back-page: flow-volume loop

Question 21

What is a peak flow meter? Normal peak flow measured?

Answer 21

Plastic flow meter that patients can take home that records peak flow

Normal: 300-500 mL/min

Question 22

Unit of peak flow on PFT?

Answer 22

mL/s

Question 23

On a PFT, what is indicated next to the FRC measure?

Answer 23

PL, N2, or He for the test used to determine RV

Question 24

On which patients should nitrogen washout and helium dilution should NOT be used to measure RV?

Answer 24

Obstructive lung disease patients because reading will not be accurate

Question 25

What are pack years of smoking?

Answer 25

Packs of cigarettes they smoke a day x years they have been doing it

Question 26

Measure on PFT that gives you an idea of how much air is being trapped inside the lungs in an obstructive lung disease?

Answer 26

RV/TLC

Question 27

If an obstructive lung disease is diagnosed but diffusion is normal, what is going on?

Answer 27

Chronic bronchitis OR asthma

Question 28

Other symptoms of sarcoidosis other than inflammation of interstitium?

Answer 28

1. Hyperpigmented raised rash plaques | 2. Dyspnea upon exertion

Question 29

Classic PFT signs of sarcoidosis?

Answer 29

1. TLC < 80% of normal predicted | 2. DLCO below normal predicted

Question 30

Do race, age, gender, and height affect all PFT expected normal values or only FEV1?

Answer 30

ALL PFT expected normal values