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

1
Q

What is the main function of the pulmonary system?

A

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

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2
Q

Respiratory demands - rest vs exercise

A

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

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

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3
Q

How do we assess ventilation?

A

use the spirometer to measure volumes and capacities

measure air flow

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4
Q

Tidal Volume (TV)

A

volume of air we are usually breathing

Normal amount is about ~½ L

can vary based on sex, age, height

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5
Q

Inspiratory Capacity (IC)

A

combination of TV and IRV

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6
Q

Vital Capacity (VC)

A

max inhale to max exhale

combination of IRV, TV, and ERV

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7
Q

Inspiratory/Expiratory Reserve Volume (I/ERV)

A

max inhalation/max exhalation

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8
Q

Reserve Volume (RV)

A

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

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9
Q

Functional Residual Capacity (FRC)

A

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

combination of ERV and RV

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10
Q

Total Lung Capacity (TLC)

A

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

combination of VC and RV

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11
Q

Ventilation

A

the bulk flow of air into/out of the lungs

Pin = alveolar pressure , Pout = barometric/atmospheric pressure

Air flows from high to low pressure

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12
Q

Mechanical ventilators are ___ ___ ventilation

A

positive pressure

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13
Q

How does air get into the lungs?

A

For air to flow into the lungs: Pin < Pout

Contraction of inspiratory muscles

Increased thoracic cavity

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14
Q

How does air get out of the lungs?

A

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

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15
Q

Properties of the thorax

A

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)

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16
Q

Properties of the lungs

A

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

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17
Q

Lung Compliance

A

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

18
Q

Pleura

A

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

19
Q

Pleural Coupling

A

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)

20
Q

Equilibrium point for lungs+thorax

A

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

21
Q

Pressure Gradient - Inspiration

A

Volume increases

Intrapleural pressure decreases

Alveolar pressure decreases
then increases back to its original point

22
Q

Pressure Gradient - Expiration

A

Volume decreases

Intrapleural pressure increases then tapers off

Alveolar pressure increases then decreases back to its original point

23
Q

Minute (total) ventilation

A

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

24
Q

Conducting Zone

A

Conducting zone = anatomic dead space

Avg ~150 mL → can increase in disease states

Air has less oxygen and more carbon dioxide → already equilibrated

25
Alveolar ventilation
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
26
Distribution of ventilation
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
27
Measures of airflow
Obtained during a max inhalation FVC, FEV1, and FEV1/FVC
28
Forced vital capacity (FVC)
telling pt to breathe as hard and as fast as they can
29
Forced Expiratory Volume in 1 second (FEV1)
volume of air exhaled in the first second Strongest indicator of pulmonary disease
30
FEV1/FVC
useful indicator of pulmonary disease, and determining obstructive or restrictive pattern of disease
31
What affects the function of the pump?
Muscle weakness Decoupling pleural membranes Tissue compliance Airway diameter Surface tension and surfactant
32
Affecting Pump - Muscle Weakness (high cervical lesion)
C3 or above Paralysis of diaphragm , requires mechanical ventilation
33
Affecting Pump - Muscle Weakness (low cervical lesion)
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
34
Affecting Pump - Decoupling Pleural Membrane
when the pleural membrane is decoupled, the thorax and lungs pull apart from each other and lose the equilibrium point Pneumothorax = collapsed lung
35
Affecting Pump - Increased Tissue Compliance
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
36
Affecting Pump - Decreased Tissue Compliance
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)
37
Affecting Pump - Surface Tension
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
38
Affecting Pump - Airway Diameter
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
39
Inspiration vs Expiration
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
40
Air flow into/out of the lungs is driven by
the pressure gradient between the alveoli and the atmosphere -Changes in the volumes of the thoracic cavity create those pressure gradients