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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
Q

How is PCO2 kept within tight limits in the body?

A

Minute ventilation is adjusted by ensuring adequate alveolar ventilation

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26
Q

Define hypoventilation

A

Alveolar ventilation too low

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27
Q

2 consequences of hypoventilation

A
  • Increased PCO2
  • Respiratory acidosis (-> increase H+ in the blood)
28
Q

Define hyperventilation

A

Alveolar ventilation too high

29
Q

2 consequences of hyperventilation

A
  • Decreased PCO2
  • Respiratory alkalosis (-> decreased H+ in the blood)
30
Q

Difference in intrapleural pressure according to gravity

A

Less negative at the bottom compared to the apex

31
Q

Difference in resting volume and expansion according to gravity

A

Bottom of the lugn has a smaller resting volume and expands better during inspiration

32
Q

Differnece in ventilation according to gravity

A

Greatest in lower zones and least in upper zones

33
Q

Regional differences in Compliance

A

Larger at bottom than at top

34
Q

Upright regional alveolar size at TLC

A
35
Q

Upright regional alveolar size at FRC

A
36
Q

Upright regional alveolar size at RV

A
37
Q

Effect of astham and increased COPD

A

Increased resistance

38
Q

Effect of lung fibrosis

A

Decreased compliance

39
Q

Effect of kyphoscoliosis

A

Deformed chest wall

40
Q

Effect of diseases that change the mechanicla properties of the lung

A

Increase respiratory workload = harder to breathe

41
Q

Define respiratory failure

A

When the respiratory system is unable to keep up and cannot accomplish its job of exchanging O2 and CO2 because of inadequate ventilation

42
Q

Type I respiratory failure

A

Decrease PaCO2

(Blood/perfusion problem)

43
Q

Type II respiratory failure

A

Increase PaCO2

(Ventilatory problem)

44
Q

Where do the bronchial veins drain into? What effect does this have?

A

Into the pulmonary veins, which drain into the left atrium, so de-oxygenated blood mixes with oxygenated blood = small “shunt”

45
Q

Effect of hyperpnea

A

Airway surface cools and dries from evaporation of fluid

46
Q

Why do the resistances of the systemic and pulmonary circuits differ?

A
  • 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
Q

Equation for resistance

A
48
Q

Define resistance

A

The impedance t oflow (the energy cost for flow)

49
Q

Define pulmonary vascular resistance (PVR)

A

Energy cost for flow in the pulmonary vasculature from the pulmonary artery to the left atrium

50
Q

Equation for PVR

A
51
Q

What determines PVR

A

Cardiac output flowing through the pulmonary arteries, capillaries and veins

52
Q

What does pulmonary vascular diameter depend on?

A

Transmural pressure across the arterial or capillary wall

53
Q

2 mechanisms that explain why PVR is lower at higher flow

A
  1. Vascular distension (increase diamter or open vessels)
  2. Vascular recruitment (open previously closed vessels)
54
Q

Effect of lung volume on alveolar vessles

A

Get smaller with increasing lung volume

55
Q

Effect of lung volume on extra-alveolar vessels

A

Get larger with increasing lung volume

56
Q

Effect of alveolar volume on spetal capillaries

A

Increased alveolar volume = stretched and narrowed septal capillaries

57
Q

Effect of alveolar pressure on septal capillaries

A

Increased alveolar pressure = compressed septal capillaries

58
Q

West Zone I characteristics

A
  • PA > Pa > Pv
  • Vessels are compressed = no flow
  • At the top of the lung when upright
59
Q

West Zone II characteristics

A
  • Pa > PA > Pv
  • PA = downstream pressure
  • ‘Vascular waterfall condition”
  • Flow depends on the difference between Pa and PA
60
Q

West Zone III characteristics

A
  • Pa > Pv > PA
  • Flow depends on arterio-venous pressure difference
61
Q

Clinical setting for zone I

A

increased PA (i.e. on a mechanical ventilator)

62
Q

Clinicla setting for Zone II

A

Increase Pa or decreased PA

63
Q

Clinical setting for Zone III

A

Increased Pv, especially in cardiac dysfunction (i.e. crackles)

64
Q

Effect of hypoxia on pulmonary vessels

A

Hypoxic pulmonary vasoconstriction (accentuated by low pH)

Note that systemic vessels vasodilate under these circumstances

65
Q

Effect of nitric oxide on pulmonary vessels

A

Pulmonary vasodilation (smooth muscle relaxation)

Block B: Respiration (4 decks)

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