PULMONARY 03: LUNG MECHANICS 2

Question 1

What are the four primary non overlapping lung volumes?

Answer 1

RV, V(total), IRV, ERV
Residual volume
Tidal volume
Inspiratory reserve volume
Expiratory reserve volume

Question 2

What is a lung capacity? How does it differ from a lung volume?

Answer 2

A lung capacity is comprised of 2+ lung volumes

meaning a lung volume is a basic unit of lung potential, and a capacity is a summation of two+ of those

Question 3

How do you measure residual volume?

Answer 3

Helium or plethysmography (you cannot use a spirometer)

Question 4

What is compliance?

Answer 4

A measure of the elastic properties of something (in this case, the lung)

Question 5

Surfactant does what to compliance?

Answer 5

Surfactant increases lung compliance

Question 6

What is going on at point 1 of the lung PV loop

Answer 6

Volume is low (we are at the residual volume)

From here, as we inspire and approach point two, pressure around the lung decreases

Question 7

What is going on at point 2 of the lung PV loop?

Answer 7

Pressure has dropped during inspiration. As pleural pressure decreases (becomes more negative), volume slowly increases, but this is low compliance. This is until a critical opening pressure is achieved (at point 2). At this point, we have achieved the pressure required to open and recruit closed pathways and alveoli.

Question 8

What is going on at point 3 of the lung PV loop?

Answer 8

Volume is going to rapidly flood into the lungs at this point (high compliance point, system is able to distend and collapse with smaller changes in pressure)

Question 9

What is going on to get to point 4 on the lung PV loop?

Answer 9

There is a decrease in compliance as TLC is reached; then, as we expire, “pleural pressure” increases because we are no longer contracting external intercostals and diaphragm. The lung volume returns toward residual volume

Question 10

What is point 5 on the lung PV loop referring to?

Answer 10

Point 5 is referring to hysteresis

Question 11

What is hysteresis?

Answer 11

Non-recoverable work required to inflate the lungs

Question 12

What is hysteresis proportional to?

Answer 12

DeltaP between inflation and deflation

Question 13

What is the impact of surfactant on the PV loop?

Answer 13

Surfactant deceases pressure necessary to open. If you do not have surfactant (blue loop) it takes WAY more pressure to open airways and you lose way more energy (hysteresis)

Question 14

What is elastic recoil of the lungs attributable to?

Answer 14

Its elastic properties and surfactant

Question 15

What does fibrosis lead to?

Answer 15

A loss of compliance (tissue is tougher)

this would cause high elastance

Question 16

What does emphysema lead to?

Answer 16

A gain of compliance (lungs become more stretchy, too stretchy)

Question 17

Air flow is (turbulant/laminar) in the large airways, and (turbulant/laminar) in the small airways of conducting zone?

Answer 17

Turbulent; laminar (and transitional)

Question 18

AWR (airway resistance) is most dependent on:
A.) Length of airway
B.) Radius of airway
C.) Viscosity of air
D.) Airway resistance is whatever you want it to be

Answer 18

Radius of the airway
Remember, this is the same resistance formula we talked about with jonathan
R= L8viscosity/(r^4 * pi)

Question 19

Do we count the resistance of airways in the lungs as a series, or in parallel? What does this mean for the total resistance?

Answer 19

Parallel

therefore, the total resistance is less than the individual components

Question 20

Because modulating the radius of an airway changes the resistance, we know that it therefore also alters
A.) Flow
B.) viscosity

Answer 20

Flow

Question 21

What is the effect on airway resistance as you increase lung volume?

Answer 21

As you increase lung volume, airway resistance decreases

Question 22

What happens if you decrease cross-sectional area of an airway?

Answer 22

The resistance of the airway increases

Question 23

Airway resistance is dependent on what three things

Answer 23

Lung volume
smooth muscle
mucus/edema

Question 24

What does it mean if you have a restrictive lung disease?

Answer 24

The lungs cannot inflate

They display a reduced cmpliance and volumes (FrC/TLC/etc are reduced)

Question 25

What does it mean if you have an obstructive lung disease

Answer 25

There is increased resistance in the airways
This means you have a reduced flow
Parameters like FEV1 will be reduced

Question 26

The equal pressure point, with regard to lungs, is what?

Answer 26

The point at which pressure inside and surrounding airways is the same

Question 27

During forced expiration, what limits airflow?

Answer 27

Dynamic compression of airways

Question 28

Work of breathing at tidal volume is high, or low?

Answer 28

Low

Patients will try to adjust breathing to minimize the work of breathing

Question 29

How do we treat obstructive diseases like asthma?

Answer 29

B2 agonists like inhalers can help dilate airways