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Block B: Respiration > Physiology Lecture 3: Lung Dynamics > Flashcards

Physiology Lecture 3: Lung Dynamics Flashcards

1
Q

6 respiratory muscles

A
  1. Diaphragm
  2. Inspiratory intercostal muscles
    • External intercostals
    • Parasternal intercostals
  3. Accessory muscles
    • Scalenes
    • Sternocleidomastoids
    • Trapezius
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2
Q

What drives normal expiration (i.e. not during exercise)

A

Passive elastic recoil pressure of the lung

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3
Q

Expiratory muscles (i.e. during exericse) (5)

A
  1. Abdominal muscles
    • Rectus abdominis
    • Transverse abdominis
    • Internal obliques
    • External obliques
  2. Thoracic muscles
    • Internal intercostal muscles
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4
Q

Number of generations in the airway structure

A

23

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5
Q

2 zones of the airways

A

Conducting zone

Respiratory zone

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6
Q

How many generations does the conducting zone contain?

A

First 16

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7
Q

Typical tidal volume at rest

A

500 mL

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8
Q

Approximate increase in tidal volume with exercise

A

3 L or more

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9
Q

3 types of lung compartment ventilation

A

VE = minute ventilation

VA = Alveolar ventilation

VD = Dead Space ventilation

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10
Q

Definition of minute ventilation

A

Total volume of fresh gas drawn into the lungs each minute

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11
Q

Equation for minute ventilation

A

VE = f x VT

where:

  1. f = respiratory rate
  2. VT = tidal volume
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12
Q

normal respiratory rate

A

12 - 20 breaths/minute

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13
Q

Approx vol of anatomical dead space

A

150 mL

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14
Q

Requirement for gas exchange in terms of VT and VD

A

VT > VD

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15
Q

Define physiological dead space

A

Anatomic dead space + non-functional alveoli

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16
Q

Define anatomic dead space ventilation

A

The volume of fresh gas reaching the anatomic dead space each minute

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17
Q

Define alveolar ventilation

A

The volume of fresh gas reaching the respiratory zone each minute

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18
Q

Equation for alveolar ventilation

A

V(dot)A = f x (VT - VD)

Where VD = dead space bolume (NOT ventilation)

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19
Q

2 equations for minute ventilation

A

VE = VA + VD

VD = VE - VA

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20
Q

Typical PAO2

A

100 mm Hg

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21
Q

Typical PACO2

A

40 mm Hg

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22
Q

Typical PiO2

A

149 mm Hg

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23
Q

Typical PiCO2

A

0 mm Hg

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24
Q

What determines PACO2

A

The ratio os CO2 production and alveolar ventilation

PACO2 α VCO2/VA

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25
How is PCO2 kept within tight limits in the body?
Minute ventilation is adjusted by ensuring adequate alveolar ventilation
26
Define hypoventilation
Alveolar ventilation too low
27
2 consequences of hypoventilation
* Increased PCO2 * Respiratory acidosis (-\> increase H+ in the blood)
28
Define hyperventilation
Alveolar ventilation too high
29
2 consequences of hyperventilation
* Decreased PCO2 * Respiratory alkalosis (-\> decreased H+ in the blood)
30
Difference in intrapleural pressure according to gravity
Less negative at the bottom compared to the apex
31
Difference in resting volume and expansion according to gravity
Bottom of the lugn has a smaller resting volume and expands better during inspiration
32
Differnece in ventilation according to gravity
Greatest in lower zones and least in upper zones
33
Regional differences in Compliance
Larger at bottom than at top
34
Upright regional alveolar size at TLC
35
Upright regional alveolar size at FRC
36
Upright regional alveolar size at RV
37
Effect of astham and increased COPD
Increased resistance
38
Effect of lung fibrosis
Decreased compliance
39
Effect of kyphoscoliosis
Deformed chest wall
40
Effect of diseases that change the mechanicla properties of the lung
Increase respiratory workload = harder to breathe
41
Define respiratory failure
When the respiratory system is unable to keep up and cannot accomplish its job of exchanging O2 and CO2 because of inadequate ventilation
42
Type I respiratory failure
Decrease PaCO2 | (Blood/perfusion problem)
43
Type II respiratory failure
Increase PaCO2 | (Ventilatory problem)
44
Where do the bronchial veins drain into? What effect does this have?
Into the pulmonary veins, which drain into the left atrium, so de-oxygenated blood mixes with oxygenated blood = small "shunt"
45
Effect of hyperpnea
Airway surface cools and dries from evaporation of fluid
46
Why do the resistances of the systemic and pulmonary circuits differ?
* Systemic blood flow actively directs to various organs = may require high pressure * Lung rarely directs blood to any one region = arterial pressure just high enough to lift blood to the top of the lung
47
Equation for resistance
48
Define resistance
The impedance t oflow (the energy cost for flow)
49
Define pulmonary vascular resistance (PVR)
Energy cost for flow in the pulmonary vasculature from the pulmonary artery to the left atrium
50
Equation for PVR
51
What determines PVR
Cardiac output flowing through the pulmonary arteries, capillaries and veins
52
What does pulmonary vascular diameter depend on?
Transmural pressure across the arterial or capillary wall
53
2 mechanisms that explain why PVR is lower at higher flow
1. Vascular distension (increase diamter or open vessels) 2. Vascular recruitment (open previously closed vessels)
54
Effect of lung volume on alveolar vessles
Get smaller with increasing lung volume
55
Effect of lung volume on extra-alveolar vessels
Get larger with increasing lung volume
56
Effect of alveolar volume on spetal capillaries
Increased alveolar volume = stretched and narrowed septal capillaries
57
Effect of alveolar pressure on septal capillaries
Increased alveolar pressure = compressed septal capillaries
58
West Zone I characteristics
* PA \> Pa \> Pv * Vessels are compressed = no flow * At the top of the lung when upright
59
West Zone II characteristics
* Pa \> PA \> Pv * PA = downstream pressure * 'Vascular waterfall condition" * Flow depends on the difference between Pa and PA
60
West Zone III characteristics
* Pa \> Pv \> PA * Flow depends on arterio-venous pressure difference
61
Clinical setting for zone I
increased PA (i.e. on a mechanical ventilator)
62
Clinicla setting for Zone II
Increase Pa or decreased PA
63
Clinical setting for Zone III
Increased Pv, especially in cardiac dysfunction (i.e. crackles)
64
Effect of hypoxia on pulmonary vessels
Hypoxic pulmonary vasoconstriction (accentuated by low pH) Note that systemic vessels vasodilate under these circumstances
65
Effect of nitric oxide on pulmonary vessels
Pulmonary vasodilation (smooth muscle relaxation)

Block B: Respiration (4 decks)

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