Brs - Physiology - Respiratory

Front 1

What is tidal volume (TV)?

Back 1

Volume of air inspired / expired with normal breaths

Front 2

What is inspiratory reserve volume (IRV)?

When is it used?

Back 2

Amount of air capable of being inspired beyond that the peak of tidal volume (TV)

Used during:
- Exercise
- Respiratory distress

Front 3

What is expiratory reserve volume (ERV)?

Back 3

Volume of air capable of being exhaled beyond the trough of tidal volume (TV)

Front 4

What is residual volume (RV)?

Back 4

Volume of air in lungs that remains beyond expiratory reserve volume (ERV)

Front 5

What is dead space?

What are the two types of dead space?

Back 5

Volume of air in lungs that does not take part in gas exchange

Two types of dead space:
- Anatomical dead space:
- Volume of air in conducting airways
- Physiological dead space:
- Volume of lungs not participating in gas exchange

Front 6

How is physiologic dead space calculated?

Back 6

V(D) = V(TV) x [ (PA CO2 - PE CO2) / PA CO2]

V(D) = Physiologic dead space
V(TV) = Tidal volume
PA CO2 = Alveolar gas partial pressure of CO2
= Arterial blood partial pressure of CO2
PE CO2 = Expired gas partial pressure of CO2

Front 7

What are the two ventilation rates?

How are they calculated?

Back 7

Minute ventilation = TV x breaths/min.

Alveolar ventilation = (TV - DS) x breaths/min.

Front 8

What is inspiratory capacity?

Back 8

IRV + TV

Front 9

What is functional residual capacity (FRC)?

Back 9

Volume in lungs after TV is expired

ERV + RV

Front 10

What is vital capacity (VC) / forced vital capacity (FVC)?

Back 10

Air that can be forced out after a maximal inspiration

IRV + TV + ERV

Front 11

What is total lung capacity (TLC)?

Back 11

IRV + TV + ERV + RV

Front 12

What is forced expiratory volume (FEV1)?

How is a normal FEV1 expressed and what is a normal value?

Back 12

Volume of air expired in 1st second of forced maximum expiration

FEV1 / FVC = 0.8
(A normal FEV1 is ~80% of FVC)

Front 13

How is FEV1 affected in obstructive lung diseases?

What is the reasoning behind this?

Back 13

Decrease in FEV1 / FVC ratio
(< 0.8)

This is because the pathological decrease in FEV1 is greater than the pathological decrease in FVC

Front 14

How is FEV1 affected in restrictive lung diseases?

What is the reasoning behind this?

Back 14

FEV1/FVC remains about normal or can increase
( ≥ 0.8)

This is because the pathological decrease in FEV1 ~ pathological decrease in FVC

Front 15

Back 15

Front 16

What is a normal anatomical dead space volume?

Back 16

~150 mL

Front 17

What are the muscles of inspiration?

Back 17

Diaphragm

External intercostals

Accessory muscles

Front 18

What are the muscles of expiration?

Back 18

Abdominals

Internal intercostals

Front 19

What is meant by respiratory "compliance?"

What properties influence compliance and how do they relate?

Back 19

"Destensibility of the lungs and chest wall"
- Ability of the lungs and chest wall to undergo a change in volume per given change in pressure

C = V / P

Inversely related to elastance
Inversely related to stiffness

Front 20

What is transmural pressure?

Back 20

Difference between alveolar pressure and intrapleural pressure

P(A) - P(intrapleural)

Front 21

What is hysteresis?

Back 21

Difference in Volume vs. Pressure curves during inspiration and expiration

Front 22

How does the compliance of the lung-chest wall system compare with the compliance of lungs and chest wall alone?

Back 22

Compliance of lung-chest wall system is less than the compliance of lungs and chest wall alone

Front 23

How does air pressure in the lungs and airways compare with atmospheric pressure at rest?

How do these pressures affect the lung and chest wall?

Back 23

P(lungs and airways) = P(ATM)

P(ATM) creates a collapsing force on the lung

P(airways / lungs) creates an expanding force on the chest wall

Front 24

Is intrapleural pressure negative, positive, or zero at rest?

Back 24

Negative

Front 25

What causes a pneumothorax?

How is intrapleural pressure affected during a pneumothorax?

How are the lungs and chest wall affected by a pneumothorax?

Back 25

Air enters intrapleural space

P(intrapleural) = P(ATM)

Lungs collapse
Chest wall moves outward

Front 26

How does compliance change in obstructive vs. restrictive respiratory disorders?

Back 26

Obstructive: Compliance ↑

Restrictive: Compliance ↓

Front 27

How does FRC change in obstructive and restrictive respiratory disorders?

Back 27

Obstructive: FRC ↑
Restrictive: FRC ↓

Front 28

What causes alveolar surface tension?

Back 28

Attractive intermolecular forces between liquid molecules lining the alveoli

Front 29

How does alveolar surface tension affect the alveoli?

What are the factors that influence this effect?

Back 29

Alveolar surface tension creates a collapsing pressure on the alveoli

LaPlace's law:
- P = (2T) / R

P = collapsing pressure (dynes / cm2)
T = surface tension (dynes / cm)
R = alveolar radius (cm)

Front 30

What are easier to keep open: large or small alveoli?

Back 30

Large alveoli are easier to keep open that small alveoli

Front 31

What is atelactasis?

What usually causes this?

Back 31

Collapse of small alveoli

Absence of sufficient surfactant

Front 32

How does surfactant affect surface tension and compliance?

Back 32

Reduces surface tension by disrupting intermolecular bonds

Increases compliance

Front 33

What cells synthesize surfactant?

Back 33

Type II alveolar cells

Front 34

What is the main molecule in surfactant?

Back 34

Dipalmitoyl phosphatidylcholine (DPPC)

Front 35

When in fetal life is surfactant present?

Back 35

Early as 24th week

Surely by 35th week

Front 36

What causes neonatal respiratory distress syndrome?

Back 36

Premature birth and lack of surfactant

Front 37

How is airflow related to pressure and resistance?

Back 37

Q = ΔP / R

Q = airflow (mL / min)
P = pressure gradient (cm H20)
R = resistance (cm H20 / L / min)

Front 38

What factors influence airway resistance and in what relationship do they do so?

Back 38

R = 8ηl / πr(^4)

Front 39

In which airways is resistance highest?

Back 39

Medium-sized bronchi

Front 40

How does lung volume affect airway resistance?

Back 40

High lung volume → radial traction↑ → resistance↓

Low lung volume → radial traction↓ → resistance↑

Front 41

How does alveolar pressure compare with atmospheric pressure at rest?

Back 41

Equilibrium

Front 42

How does intrapleural pressure change with inspiration?

Back 42

Becomes more negative

Front 43

Back 43

Front 44

Back 44

Front 45

What is the difference between perfusion-limited and diffusion-limited gas exchange?

What are examples of diffusion-limited and perfusion-limited gas exchange?

Back 45

Perfusion-limited gas exchange:
- Gas partial pressures equilibrate early along the distance of the capillary
- Diffusion can only be increased by increased perfusion

Perfusion-limited gas exchange:
- Gas partial pressures do not equilibrate by the end of the capillary

Examples:
- Diffusion-limited:
- O2
- CO2
- N2O
- Perfusion-limited
- Emphysema
- Fibrosis
- CO