Pulmonary function tests

Question 1

What is pulmonary mechanics?

Answer 1

Effort dependent results related to spirometry.

Question 2

What values are associated with pulmonary mechanics?

Answer 2

FEV1, VC, FEV1/FVC ratio, and MVV (maximal voluntary ventilation).

Question 3

What is pulmonary function?

Answer 3

Results from spirometry, lung volume, and gas exchange assessment.

Question 4

What values are associated with pulmonary function?

Answer 4

RV, TLC, and DLCO (all of these cannot be obtained with spirometry).

Question 5

What values are associated with muscle forces?

Answer 5

MIP/MEPs (maximal inspiratory and expiratory pressures).

Question 6

What is characteristic of obstructive lung defects?

Answer 6

Expiratory flow is below normal (FEV1/FVC, FEV1).

Question 7

What is characteristic of restrictive lung defects?

Answer 7

Lung volumes are reduced (TLC).

Question 8

What is slow vital capacity (SVC)?

Answer 8

Measure of volume during slow expiration (as opposed to FVC which is fast). It presents with less opportunity for dynamic collapse of airways than FVC.

Question 9

What does a SVC>FVC suggest?

Answer 9

It could suggest air trapping (gas left behind in the lungs due to dynamic collapse of the airways during forced expiration, as can be seen in emphysema).

Question 10

What is maximum voluntary volume (MVV)?

Answer 10

When the patient breathes as fast and deep as possible for 12-15 seconds.

Question 11

What does maximum voluntary ventilation (MVV) assess?

Answer 11

It assesses respiratory stamina. It is decreased in obstructive disorders, with the decline in percentage predicted paralleling the FEV1/FVC ratio.

Question 12

What is FEV3?

Answer 12

Evaluates flow three seconds into expiration. It reflects airflow in the smaller airways.

Question 13

What airways permit flow?

Answer 13

Large airways.

Question 14

What airways distribute flow?

Answer 14

Small airways.

Question 15

What does FEV1 express?

Answer 15

The maximal volume exhaled in one second. It assesses the flow characteristics of the larger airways.

Question 16

What does an MVV less than the FEV1 suggest?

Answer 16

It could indicate neuromuscular weakness or deconditioning.

Question 17

What is the peak expiratory flow rate (PEFR)?

Answer 17

The maximum flow rate achieved during an FVC. It is equivalent to the “peak flow meter” used by asthmatics.

Question 18

What is the time constant?

Answer 18

The time it takes to drain 63% of a space (such as the lungs)

Question 19

What determines the time constant?

Answer 19

Time constant = resistance X capacitance (compliance of the alveoli). Increased resistance or increased compliance will increase the time constant.

Question 20

What change will occur on the flow volume loop in obstructive diseases?

Answer 20

Obstructive diseases will typically have a concave F/V loop.

Question 21

What change will occur on the flow volume loop in extrathoracic compressions (outside the lung)?

Answer 21

Inspiration is decreased.

Question 22

What change will occur on the flow volume loop in intrathoracic compressions (inside the lung)?

Answer 22

Expiration is decreased.

Question 23

What change will occur on the flow volume loop in fixed compressions (all along the respiratory tract)?

Answer 23

Both expiration and inspiration are decreased.

Question 24

How is effort independent flow effected at higher volumes?

Answer 24

At higher volumes, it takes higher effort and higher flow to reach effort independent flow.

Question 25

How is effort independent flow effected at lower volumes?

Answer 25

At lower volumes, it takes lower effort and lower flow to reach effort independent flow (i.e. at lower volumes effort independent flow is reached sooner and takes up a longer portion of forced expiration).