Ventilation

Question 1

Anatomic Dead Space

Answer 1

Space in conducting system up to terminal bronchioles, which doesn’t facilitate gas exchange. About 150 mL/lb

Question 2

Why Pressure in Venous Blood (706) < Arterial Blood (755)

Answer 2

pO2 decreases from 95 to 40 cause we remove it, and we add less CO2 (and CO2 can be transported as other compounds)

Question 3

Tidal Volume (TV)

Answer 3

Volume fluctuation during normal resting breathing, about 500 mL

Question 4

Functional Residual Capacity (FRC)

Answer 4

Volume of gas in lungs at end of resting expiration, = ERV + RV

Question 5

Expiratory Reserve Volume (ERV)

Answer 5

Maximum expiration from resting expiratory level to maximum expiratory level (about 1 L)

Question 6

Inspiratory Reserve Volume (IRV)

Answer 6

Maximum inspiration from top of tidal volume to maximum inspiratory level (about 3L)

Question 7

Inspiratory Capacity

Answer 7

Volume b/w resting expiratory level and maximum inspiratory level ( = TV + IRV)

Question 8

Vital Capacity

Answer 8

Maximum inspiratory volume to maximum expiratory level (= IRV + TV + ERV)

Question 9

Residual Volume

Answer 9

Fixed amount of gas that can’t be expired, about 1.2 L

Question 10

How to Estimate RV

Answer 10

Use helium bc insoluble in blood, put in known conc in known volume of spirometer and let person breath to equilibrate. Then you can just calculate w/:
C(HeSp) x Vsp = C(He Equil) x ( Vsp + RV)

Question 11

Dynamic Lung Volumes (explanation and normal/2 pathological conditions)

Answer 11

Measure Forced Expired Volume in 1 sec (FEV1) and Forced Vital Capacity (FVC)
In normal pt, FEV1/FVC ~ 0.8
In asthmatic, obstructive block so FEV1/FVC < 0.8
In fibrotic (restrictive) pt, FEV1/FVC >= 0.8 (bc FVC isn’t much itself)

Question 12

Peak Expiratory Flow and Effort Dependence

Answer 12

On expiration, increasing part of curve is effort dependent but decreasing is independent because P collapses airways. This doesn’t happen in inspiration because airways stay open

Question 13

PEF and Diseases

Answer 13

Decreased in both obstructive disease and restrictive disease, but lung volume is much larger than normal in obstructive (bc of compensation measures, huge RV though) and smaller in restrictive

Question 14

Minute Volume

Answer 14

Amount of expired gas/minute = Respiratory rate x TV

Question 15

Alveolar Ventilation

Answer 15

(tidal volume - dead space) x respiratory rate

Question 16

2 Primary Muscles of Inspiration

Answer 16

Diaphragm (main) and external intercostals bc lift ribcage up, increase front-back diameter

Question 17

2 Accessory Muscles of Inspiration

Answer 17

Sternocleidomastoids and scalenes

Question 18

2 Muscles in Expiration

Answer 18

Internal intercostals (bc lower ribcage) and abdominal muscles

Question 19

Transpulmonary Pressure =

Answer 19

Alveolar pressure (about 1 atm) - intrapleural pressure

Question 20

Hysteresis

Answer 20

Difference in pressure required for certain amount of inflation and deflation: it is a property of surfactant that it is more difficult to stretch than to maintain stretch

Question 21

Atelectasis

Answer 21

Collapse of alveoli

Question 22

Compliance of Lung

Answer 22

Change in V/Change in P, about 0.2 L/cm H2O

Question 23

Laplace Surface Tension Eq

Answer 23

Pressure = 4xTension/Radius (or 2xTension/Radius if only one surface is involved

Question 24

Problem w/ no Surfactant

Answer 24

Smaller alveoli would have higher pressure, so air would leave them and continually inflate larger alveoli

Question 25

3 Functions of Surfactant

Answer 25

1. Reduces surface tension, increasing compliance and decreasing force needed to inflate lungs
2. Stabilizes alveoli bc as SA decreases (smaller alveoli), surfactant conc is higher so surface tension decreases and low pressure causes air to travel from larger alveoli to smaller
3. Keeps alveoli dry bc reduced surface tension decreases effect of drawing water out of capillaries

Question 26

Alveolar Interdependence

Answer 26

Neighboring alveoli keep each other open

Question 27

Lung and Chest Wall Natural Tensions

Answer 27

Each require about 5 cm H2O (in opposite directions) just to keep at Resting Expiratory Level, so P is about 0 there. However together lung-chest wall system has shallower slope than either lung or chest wall alone bc in series

Question 28

Compliance in Series

Answer 28

1/C = 1/C1 + 1/C2 (like lung and chest wall, so takes more effort to move the two together)

Question 29

Compliance in Parallel

Answer 29

C = C1 + C2 + … (like two lungs and alveoli, so if you remove 1 or part of 1 harder to breathe bc decreased compliance)

Question 30

Pneumothorax

Answer 30

With hole in chest wall, chest wall is able to expand and lung able to collapse like they want. All pressures equalize to 0

Question 31

Resistance to flow =

Answer 31

K/Radius^4

Question 32

Rate of Flow =

Answer 32

Pressure difference/resistance

Question 33

Lung Volume and Resistance

Answer 33

Greater lung volume = less resistance, because elastic tissue actually pulls in every direction on airways keeping them open

Question 34

Check Valve Mechanism

Answer 34

Transairway pressure is negative bc pressure outside airway is larger than P inside airway, so airway can collapse