Pulmonary Function Tests

Question 1

What is the difference between capacities and volumes?

Answer 1

Volumes can be directly measured or at least estimated

Capacities are a sum of at least 2 volumes

Question 2

What are the 3 patterns of disease you can see on PFT?

Answer 2

Obstructive
Restrictive
Mixed

Question 3

How is residual volume measured?

Answer 3

It’s not, it has to be estimated based on previous measures of other dead people

Question 4

What makes up functional residual capacity?

Answer 4

ERV and RV

Question 5

What is the significance of the functional residual capacity!? TEST QUESTION

Answer 5

it is when the system is at equilibrium. It is the volume at which elastic recoil of the lung is balanced by desire of the chest wall

Question 6

What comprises the functional residual capacity?

Answer 6

Sum of ERV and RV

this requires effort

Question 7

What comprises the total lung capacity?

Answer 7

RV, ERV, TV, IRV
requires effort
requires estimation of RV

Question 8

What is a normal airflow spirometry test?

Answer 8

6 second expiratory time
curved plateau for at least 1 second
you have to reproduce the test 3 times and do the maneuvers within 200 mL

Question 9

What is a normal FEV1/FVC?

Answer 9

0.8

Question 10

what is the hallmark of obstructive lung disease?

Answer 10

Reduced FEV1/FVC

Question 11

How do you diagnose restrictive disease on spirometry?

Answer 11

You can’t diagnose restrictive diseases solely by spirometry. You must have lung volumes to accompany them. This is because FEV1/FVC can either be elevated or preserved

Question 12

What portion of expiration is “effort independent” and how does this show up on a flow volume loop?

Answer 12

The latter 2/3rd of expiration are effort independent meaning that the rate of expiration will not increase with effort. This shows up as a linear decline in flow on the flow volume loop. This portion of the curve is solely determined by the elastic recoil of the lung and airway resistance

Question 13

Which limb of the flow volume loop is typically symmetric?

Answer 13

inspiration side

Question 14

How will obstructive disease show up on a flow volume loop?

Answer 14

Left shift with “caving”

Question 15

how will restrictive disease show up on a flow volume loop?

Answer 15

supranormal airflow with right shift

Question 16

What are the characteristics of a variable extrathoracic obstruction? What changes on the flow volume loop?

Answer 16

The obstruction is open during expiration and closed during inspiration.
Flow volume loop shows flattening of the inspiration curve

Question 17

What are the characteristics of a variable intrathoracic obstruction? What changes on the flow volume loop?

Answer 17

The obstruction is closed during expiration and open during inspiration.
Flow volume loop shows flattening of expiration

Question 18

What is a shortcut to figure out what type of variable obstruction is present from a flow volume loop?

Answer 18

draw a line from the flattest part to the pointiest part of the curve and which way the arrow points will point either up (extra thoracic) or down (intrathoracic)

Question 19

what method of obtaining lung volumes is the most accurate and which formula does it use?

Answer 19

plethysomography (does not require diffusion of gas) and it uses Boyles Law (P1V1=P2V2)

Question 20

What will be elevated in lung volumes if air trapping is present?

Answer 20

RV

Question 21

What will be elevated in lung volumes with hyperinflation?

Answer 21

TLF or FRC >120% predicted and RV >140%

Question 22

What are the characteristics of lung volumes that are restricted?

Answer 22

decreased TLC or FRC

Question 23

What are the 4 things that determine DLCO?

Answer 23

Surface area
Membrane thickness
Diffusion gradient of gas
Presence of hemoglobin

Question 24

how is DLCO measured?

Answer 24

CO breathhold for 10 seconds

you breathe in a known amount of CO and the amount of CO returned in INVERSELY PROPORTIONAL to alveolar function

Question 25

What is the DLCO in emphysema and why?

Answer 25

decreased

because there is decreased surface area

Question 26

What is the DLCO in interstitial lung disease and why?

Answer 26

decreased

because there is increased membrane thickness

Question 27

What is the DLCO in pulmonary edema or pneumonia and why?

Answer 27

decreased

because there is alveolar filling

Question 28

What is the DLCO in pulmonary vascular disease and why

Answer 28

decreased

because there is decreased pulmonary blood flow

Question 29

what is the DLCO with alveolar hemorrhage?

Answer 29

increased

Question 30

Why is it important to correct for lung volume in DLCO?

Answer 30

if the patient has a chest wall/pleural disease (obesity) or resection of the lung. You can still have normal alveolar function

Question 31

Where is asthma on a PV curve?

Answer 31

at a higher volume but has the same slope as normal

Question 32

where is emphysema on a PV curve?

Answer 32

increased volume and steeper slope

Question 33

where is obesity on a PV curve?

Answer 33

decreased volume with same slope as normal

Question 34

Where is pulmonary fibrosis on a PV curve?

Answer 34

lower volume with less steep curve

Question 35

When is a bronchodilator challenge with albuterol positive?

Answer 35

> or equal to 12% change in FEV1 and/or FVC

AND 200 cc increase in volume

Question 36

What are the 3 major factors that determine DLCO?

Answer 36

1. surface area
2. membrane thickness
3. pulmonary blood flow