Exam 6: Mechanics of Ventilation

Question 1

Describe V_T

Answer 1

Tidal volume
The volume that moves in and out of the lungs
10-15 ml/kg for 1 tidal volume

Question 2

Describe FRC

Answer 2

Functional residual capacity

2 volumes play a role in gas exchange, expiratory reserve volume and residual volume

Question 3

Describe IC

Answer 3

Inspiratory capacity

At least 2 volumes, inspiratory reserve volume and tidal volume

Question 4

Describe IRV

Answer 4

Inspiratory reserve volume
Single unit because it is a volume
IC without tidal volume

Question 5

Describe TLC

Answer 5

Total lung capacity
The maximum amount of volume that your lungs can take
All of the volume together equal this

Question 6

Describe VC

Answer 6

Vital capacity
All of the volumes together except for residual volume: Inspiratory reserve volume, tidal volume, and expiratory reserve volume

Question 7

What is expired minute ventilation? How can it be calculated?

Answer 7

A volume of lung gas per minute; breaths per minute

V ̇_E= VT x frequency

Question 8

Define compliance

Answer 8

Compliance = change in volume/change in pressure
C = ΔV / ΔP
The ability to stretch and return to original shape, like a balloon
It is vital to proper respiratory function and work of breathing

Question 9

What are the determinants of compliance behavior of the lung? Which one is the most important?

Answer 9

Elastic forces caused by surface tension (most important)

Elastic forces caused by the lung

Question 10

What is hysteresis?

Answer 10

The difference between the inflation and deflation curves of the lung

Question 11

What are the major components of surfactant?

Answer 11

Primarily primarily dipalmitoyl phosphatidylcholine (a phospholipid)
Ca++
Proteins

Question 12

What is a pneumothorax?

Answer 12

A punctured chest cavity

Question 13

Describe what happens to the lung and chest wall when a pneumothorax is induced

Answer 13

There will no longer be negative pressure there and lungs will collapse (also due to the recoil pressure)
Chest wall tends to expand

Question 14

What is static compliance?

Answer 14

The elastic properties of chest wall, elastic properties of lung, surface tension and the compliance of each

Question 15

What is a majority of static compliance determined by?

Answer 15

Surface tension

Question 16

What is dynamic complinace?

Answer 16

The compliance of components working together which will define the work of breathing

Question 17

What are the components of dynamic compliance?

Answer 17

Elastic properties of chest wall, elastic properties of lung, surface tension (these 3 are also static compliance), airway resistance, tissue resistance, and inertia

Question 18

What factors determine airway resistance?

Answer 18

Lung volume
Airway smooth muscle tone
Mucus production
RN=ρVd/n
The alveoli tend to stretch the airways as they fill

Question 19

How does dynamic compliance limit expiratory flow?

Answer 19

Resistance of the airway and tissues, as well as inertia

Question 20

Where does turbulent flow occur in the normal tracheobronchial tree?

Answer 20

Trachea

Question 21

What does interdependence of structure mean (i.e., mechanical tethering)?

Answer 21

The lungs are attached to the rib cage via negative pressure between the 2 pleural layers, known as mechanical tethering

Question 22

Use Bohr’s equation to determine physiologic dead space in a dog with a PaCO2=40 mmHg and PECO2=30 mmHg.

Answer 22

VD/VT = (PaCO2 – PECO2) / PaCO2
=(40-30)/40
=0.25