Pulmonary Physiology 1 (9/23a) [Biomedical Sciences 1]

Question 1

What is the main function of the pulmonary system?

Answer 1

Exchange oxygen and carbon dioxide between cells and the environment

Must adapt to changing demands

Ventilation, gas exchange, gas transport, ventilation-perfusion matching,
defense system

Question 2

Respiratory demands - rest vs exercise

Answer 2

Rest: VO2 250 mL/min, minute ventilation 5 L/min

Exercise: VO2 5000 mL/min, minute ventilation 100 L/min

Question 3

How do we assess ventilation?

Answer 3

use the spirometer to measure volumes and capacities

measure air flow

Question 4

Tidal Volume (TV)

Answer 4

volume of air we are usually breathing

Normal amount is about ~½ L

can vary based on sex, age, height

Question 5

Inspiratory Capacity (IC)

Answer 5

combination of TV and IRV

Question 6

Vital Capacity (VC)

Answer 6

max inhale to max exhale

combination of IRV, TV, and ERV

Question 7

Inspiratory/Expiratory Reserve Volume (I/ERV)

Answer 7

max inhalation/max exhalation

Question 8

Reserve Volume (RV)

Answer 8

the little bit of air left in our lungs after an exhale

Question 9

Functional Residual Capacity (FRC)

Answer 9

volume of air in the
lungs at the bottom of a normal exhale

combination of ERV and RV

Question 10

Total Lung Capacity (TLC)

Answer 10

capacity of air from a max inhale to max exhale plus RV

combination of VC and RV

Question 11

Ventilation

Answer 11

the bulk flow of air into/out of the lungs

Pin = alveolar pressure , Pout = barometric/atmospheric pressure

Air flows from high to low pressure

Question 12

Mechanical ventilators are ___ ___ ventilation

Answer 12

positive pressure

Question 13

How does air get into the lungs?

Answer 13

For air to flow into the lungs: Pin < Pout

Contraction of inspiratory muscles

Increased thoracic cavity

Question 14

How does air get out of the lungs?

Answer 14

For air to flow out of the lungs: Pin > Pout

Air is expelled until Pin=Pout

Diaphragm relaxes and thoracic cavity decreases

Lungs recoil and compress alveoli

Question 15

Properties of the thorax

Answer 15

Volume is large at equilibrium (Pin = Pout)

Usually wants to expand

Outside forces can cause the thorax to collapse or expand

Once outside force stops acting, thorax will return to equilibrium point

(ex: tennis ball)

Question 16

Properties of the lungs

Answer 16

At equilibrium, volume is small ( Pin = Pout )

Outside forces (muscles) generally cause the lung to expand

Once the outside force stops acting, lung collapses back to equilibrium point

Compliance

Question 17

Lung Compliance

Answer 17

Compliance = ΔV/ΔP (ex: slinky)

When volume is high → compliance is low (stiff)

When volume is low → compliance is high (stretchy)

The muscles will have to work much harder to stretch the lungs when
they are at high volume

Question 18

Pleura

Answer 18

lines the inside of the pleural cavity and outside of the lungs

Question 19

Pleural Coupling

Answer 19

pleural fluid that acts like glue and allows the lung and chest
wall to stick together

Cohesive force holds visceral and parietal pleura together

At new equilibrium point, lung partially expanded and thorax
partially collapsed

Tug of war creates produces negative Pip (because pulling apart)

Question 20

Equilibrium point for lungs+thorax

Answer 20

functional residual capacity (FRC)- point where the collapsing force of the lung is balanced by the expanding force of the thorax

During inhalation, move right on curve

During exhalation, move left on curve

Question 21

Pressure Gradient - Inspiration

Answer 21

Volume increases

Intrapleural pressure decreases

Alveolar pressure decreases
then increases back to its original point

Question 22

Pressure Gradient - Expiration

Answer 22

Volume decreases

Intrapleural pressure increases then tapers off

Alveolar pressure increases then decreases back to its original point

Question 23

Minute (total) ventilation

Answer 23

MV = tidal volume * respiratory rate

Some air stays in the conducting zone and doesn’t participate in gas exchange

Tidal Volume avg ~ 450 mL, RR 12 breaths/min → MV = 5.4 L/min

Question 24

Conducting Zone

Answer 24

Conducting zone = anatomic dead space

Avg ~150 mL → can increase in disease states

Air has less oxygen and more carbon dioxide → already equilibrated

Question 25

Alveolar ventilation

Answer 25

AV = (tidal volume - dead space volume) * respiratory rate

Alveolar ventilation (L/min) accounts for dead space

EX: (0.450 L - 0.150 L) * 12 breaths/min → AV = 3.6 L/min

Question 26

Distribution of ventilation

Answer 26

When upright, the apex of the lung is more stretched and less compliant, due to gravity

The base is more compliant and can expand more during ventilation

We can use change in position to change degree of ventilation to the lungs

Question 27

Measures of airflow

Answer 27

Obtained during a max inhalation

FVC, FEV1, and FEV1/FVC

Question 28

Forced vital capacity (FVC)

Answer 28

telling pt to breathe as hard and as fast as they can

Question 29

Forced Expiratory Volume in 1 second (FEV1)

Answer 29

volume of air exhaled in the first second

Strongest indicator of pulmonary disease

Question 30

FEV1/FVC

Answer 30

useful indicator of pulmonary disease, and determining obstructive or restrictive pattern of disease

Question 31

What affects the function of the pump?

Answer 31

Muscle weakness

Decoupling pleural membranes

Tissue compliance

Airway diameter

Surface tension and surfactant

Question 32

Affecting Pump - Muscle Weakness (high cervical lesion)

Answer 32

C3 or above

Paralysis of diaphragm , requires mechanical ventilation

Question 33

Affecting Pump - Muscle Weakness (low cervical lesion)

Answer 33

Diaphragm innervated but intercostals and abdominals are not

Contraction of diaphragm causes collapse of thoracic cage
-Upper chest paradoxical pattern

Loss of abdominals leads to flattening of diaphragm, expansion of
abdomen during inspiration → we can use abdominal binder or positioning

Question 34

Affecting Pump - Decoupling Pleural Membrane

Answer 34

when the pleural membrane is decoupled, the thorax and lungs pull apart from each other and lose the equilibrium point

Pneumothorax = collapsed lung

Question 35

Affecting Pump - Increased Tissue Compliance

Answer 35

Easier to expand lung, but it doesn’t snap back to normal resting volume
-Decreased elastic recoil

In severe cases, exhalation requires active contraction of abdominals

Destruction of airway support = airway collapse

Higher FRC (equilibrium)→ diaphragm flattened
-Decreased mechanical advantage, less efficient

Increased work of breathing
-Up to 25% of VO2 (usually 5% in healthy people)

EX: emphysema → destroys elastic fibers in lung tissue

Question 36

Affecting Pump - Decreased Tissue Compliance

Answer 36

Increased muscle effort required for inspiration and work of breathing

Lower FRC (equilibrium)→ low lung volume = smaller airway diameter

Increased resistance to flow, increased risk of airway collapse

EX: fibrosis, chest wall disorders (kyphosis, scoliosis, sarcoidosis, lupus)

Question 37

Affecting Pump - Surface Tension

Answer 37

Surface tension pushes alveoli walls in toward collapse

Surfactant produced by lung epithelium
-Reduces surface tension to keep alveoli open

Respiratory distress syndrome=loss of surfactant leads to alveolar collapse/atelectasis
-Decreased lung compliance, decreased surface area for gas exchange

Question 38

Affecting Pump - Airway Diameter

Answer 38

Resistance to airflow determined by airway diameter

Inspiration → airway diameter increases

Expiration → airway diameter decreases

• Dynamic compression - the harder we breathe, the more this airway collapse occurs
• Limits peak flow during expiration

Question 39

Inspiration vs Expiration

Answer 39

INSPIRATION

• Volume of thorax increases
• Fall in alveolar pressure causes air to move into lung

EXHALATION

• Volume of thorax decreases
• Increase in alveolar pressure causes air to move out of lung

Question 40

Air flow into/out of the lungs is driven by

Answer 40

the pressure gradient between the alveoli and the atmosphere

-Changes in the volumes of the thoracic cavity create those pressure gradients