Zhu: Pulmonary Ventilation

Question 1

How is elasticity defined?

Answer 1

The ability to resume initial form. (Think of a balloon going back to it’s initial form after you blow air in it - very elastic)

Question 2

What type of fibers aid in lung elasticity?

Answer 2

Collagen (help lung go back to its original form)

Question 3

How is compliance defined?

Answer 3

stretchiness and distensibility

Question 4

What is the relationship of elasticity and compliance?

Answer 4

They are inversely related. High elasticity means it’s strong enough to go back to it’s original form so it can’t be very stretchy = low compliance. bad balloon - blow it up and it doesn’t go back to its original form: low elasticity and high compliance

Question 5

Why is there a pressure-volume difference in inspiration and expiration (WITHOUT surfactant)?

Answer 5

Hysteresis: difference between surface tension

Question 6

How does elasticity of the lung change in emphysema?

Answer 6

elastic fibers are lost. “Destruction of the normal architecture of the lung” elasticity is decreased, so compliance is increased

Question 7

How does elasticity of the lung change in pulmonary fibrosis?

Answer 7

Elasticity is increased. Lungs are stiff. “Marked thickening of the alveolar walls (extensive collagen deposition)” Compliance is decreased, therefore it’s hard to stretch/inhale.

Question 8

The tendency of water molecules to bond together (versus water with air) _____________ surface area and ____________ surface tension.

Answer 8

decreases; increases

Question 9

What causes the increased surface tension on alveoli?

Answer 9

a gas-water interface

Question 10

What protects against collapse of alveoli with increased surface tension

Answer 10

Surfactant

Question 11

Surface tension on alveoli _______________ compliance. Surfactant _______________ surface tension.

Answer 11

decreases; decreases. (think of a tension weight on top of the alveoli): surface tension decreases compliance and makes it harder to expand. Surfactant reduces the surface tension so alveoli can expand.

Question 12

Your patient has a hard time on inhalation. You suspect her problem to be due to a loss of what type of cell?

Answer 12

alveolar Type II epithelial cells (they make surfactant)

Question 13

Your patient has a hard time on inhalation. You suspect to find a decrease in?

Answer 13

-Ca2+ -DPPC (phospholipid dipalmitoyl phosphatidycholine) (*major component of surfactant) surfactant apoproteins

Question 14

Your patient is pregnant at 25 weeks and is asking what complications she may have if she goes into labor this week or next. What do you tell her?

Answer 14

Baby will be a risk of IRDS: infant respiratory distress syndrome preemies have a hard time breathing due to lack of enough surfactant. It begins production around 24-28 weeks of gestation and gets to be sufficient around 35 weeks gestation.

Question 15

Pressure and surface tension equation

Answer 15

P=(2*Surface tension)/Radius of alveolus surface tension is decreased by surfactant. a larger radius will have a decreased surfactant to alveolar surface area ratio and thus higher surface tension INCREASED PRESSURE IS THE DRIVING FORCE FOR MOVEMENT

Question 16

***Three main functions of surfactant?

Answer 16

1. increased COMPLIANCE (by huge reduction in ST) 2. Promote alveoli STABILITY 3. Keeps alveoli DRY

Question 17

***Lack of surfactant leads to?

Answer 17

1. reduced COMPLIANCE 2. alveolar ATELACTASIS (collapse) 3. Pulmonary EDEMA (lungs wet)

Question 18

What is airflow frictional resistance due to?

Answer 18

20% tissue or viscous resistance (lung parenchyma, chest wall, abdominal structures) 80% airway resistance

Question 19

What are the muscles of expiration and are they active or passive?

Answer 19

PASSIVE. (diaphragm relaxes) -INternal intercostals -abdominal muscles (during exercise)

Question 20

What are the muscles of inspiration and are the active or passive?

Answer 20

ACTIVE. (diaphragm pushes down and out/lung vol is increased) -diaphragm -EXternal intercostals (during exercise) -also during exercise: SCM, anterior serratus, scalene muscles, alas nasi (nose)

Question 21

Given Boyle’s Law, how are pressure and volume related?

Answer 21

Inversely proportional P1V1 = P2V2

Question 22

Normal atmospheric pressure?

Answer 22

760 mmHg. In medicine = reference point is 0. So if P=+5; it’s 765.

Question 23

What is the normal intrapleural pressure?

Answer 23

-5 cm H2O

Question 24

On inspiration, the pleural pressure ___________.

Answer 24

decreases. Goes from -5 to -8.

Question 25

On expiration, the pleural pressure _________.

Answer 25

increases. (back up to -5 from -8)

Question 26

What is the intrapleural pressure maintained by?

Answer 26

lymph constantly taking water away; water being produced elsewhere….

Question 27

**What happens in a pneumothorax?

Answer 27

Air enters the intrapleural space. This is the area that maintains the -5 pressure, keeping the lungs in place and preventing collapse. INTRAPLEURAL PRESSURE WILL INCREASE from -5 to 0. Air pressure outside the lungs is greater, so air will rush into the lesser pressure area to balance it out. This will in turn cause the lungs to collapse as it no longer has the in-tact intrapleural space to maintain the negative pressure necessary to hold them in place. Causes: trauma, rupture, surgery

Question 28

What happens to alveolar (intrapulmonary) pressure on inspiration and expiration?

Answer 28

Inspiration: alveolar pressure decreases and volume increases Expiration: opposite (Net movement is from higher pressure to lower pressure)

Question 29

**What is transpulmonary pressure?

Answer 29

Pressure difference between alveolar (intrapulmonary) pressure and intrapleural pleural pressure. (alveolar pressure MINUS intrapleural pressure) Should be always positive - tells you lung is well-inflated.

Question 30

What are the 4 pulmonary volumes and 4 pulmonary capacities?

Answer 30

**remember on the exam: volume has no overlay. capacitiy = 2 or more volumes.

Volumes (TIRE):

Tidal Volume (TV) (500)

Inspiratory reserve volume (IRV) (exercise)

Expiratory reserve volume (ERV)

Residual Volume (RV)

Capacities:

Inspiratory capacity: TV+IRV

Functional Residual Capacity: ERV+RV

Vital Capacity: TV+IRV+ERV

Total lung capacity: TC+IRV+ERV+RV

Question 31

**Minute respiratory volume

Answer 31

How much air you breathe in a minute:

TV*respiratory rate = 500*12 = 6000 ml/min

Question 32

Which volumes and capacities can a spirometer measure?

Answer 32

Volumes: TV, IRV, ERV (NOT residual)

Capacities: Vital capacity, inspiratory capacity (NOT functional or total)

Question 33

How can you measure your patient’s functional residulal capacity, total lung capacity, and residual volume?

Answer 33

Method of Helium Diultion:
FRC= [(Ci/Cf)-1]*ViSpir

RV=FRC-ERV

TLC=FRC+IC

Question 34

What is the forced vital capacity in normal lungs (amount out in the first second of expiration)?

Emphysema?

Fibrosis?

Answer 34

Normal: 80%

Emphysema (obstructive; low elasticity): 42%

FIbrosis: (high elasticity, low compliance. can’t get air in well but can get it out very well): 90%

Question 35

What happens to airway resistance during expiration?

Answer 35

it increases. volume and radius go down; therefore Resistance increases.

Question 36

Dead Space and Alveolar Ventilation

Answer 36

ideal: physiologic = anatomic, so all air participates in gas exchange.

Alveolar ventilation (Va): the total volume of new air that reaches respiratory unit per minute.

Va = RR * (TV-Physiological dead space)

= 12*(500-150) = 4200 ml