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Physiology Part 2 > Lec 34 Ventilation and perfusion > Flashcards

Lec 34 Ventilation and perfusion Flashcards

1
Q

What makes up the conducting zone of respiratory system?

A
  • nose
  • nasopharynx
  • larynx
  • trachea
  • bronchi
  • bronchioles [terminal]
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2
Q

What is function of conducting zone?

A

warm, humidify, and filter air

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3
Q

What is structure of conducting zone?

A
  • contains mucus-secreting glands, cilia, smooth muscle
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4
Q

What makes up the respiratory zone of respiratory system?

A
  • respiratory bronchioles
  • alveolar ducts
  • alveolar sacs
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5
Q

Are terminal bronchioles part of conducting or respiratory zone?

A

conducting

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6
Q

What are two functions of respiratory zone?

A
  • gas exchange

- surfactant production

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7
Q

What is structure of respiratory zone?

A
  • elastic fibers

- epithelial cells [type I and II pneuomocytes]

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8
Q

What is dead space?

A

the volume of airways and lungs that does not participate in gas exchange

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9
Q

What is anatomic dead space? value?

A
  • volume of conducting airway

- 150 mL

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10
Q

What is physiologic dead space?

A
  • the total volume of lungs [including airways] that does not participate in gas exchange
  • Physiologic dead space = anatomic dead space + functional dead space
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11
Q

What is functional dead space? What is reason for functional dead space

A
  • ventilated alveoli that do not participate in gas exchange

- due to mismatch of ventilation and perfusion

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12
Q

What is the volume of anatomic dead space?

A

150 mL

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13
Q

What is anatomic dead space made of?

A
  • nose/mouth
  • trachea
  • bronchi
  • non-respiratory [terminal] bronchioles
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14
Q

What are low and upper limits of tidal breath normally?

A

150 mL to 500 mL

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15
Q

What is tidal volume? How much of tidal volume participates in gas exchange

A

TV = 500 mL

350 mL participates in gas exchange, 150 mL is anatomic dead space

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16
Q

In normal conditions what is relationship physiologic dead space and anatomic dead space?

A

normally physio dead space = anatomic
because functional dead space is minimal
due to good matching of ventilation and perfusion

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17
Q

How do you measure physiologic dead space?

A
  • if dead space present, the air from dead space does not undergo gas exchange thus wil contain no CO2. air from exchanged alveoli will have CO2
  • measure difference between PCO2 from pure alveolar gas and PCO2 from expired air
  • lower PCO2 in expired air means it has been diluted by dead space
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18
Q

3 assumptions for measuring volume of physiologic dead space

A
  1. all CO2 in expried air comes from exchange of CO2 in functioning [V and Q] alveoli
  2. there is no CO2 in inspired air
  3. physiologic dead space contribute no CO2 since they don’t exchange gases
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19
Q

What is equation for volume of dead space?

A

Vd = Vt * [PaCO2 - PeCO2]/PaCO2

Vd = volume dead space, Vt = tidal volume,  PaCO2 = arterial PCO2 [assumes this = alveolar]
PeCO2 = expired air PCO2
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20
Q

What is equation for Vd/Vt?

A 
Vd/Vt = [PaCO2 - PeCO2] / PaCO2
a = arterial, e = expired
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21
Q

What is Vd/Vt with tidal volume 0.5 L, arterial blood gas 40 mmHg CO2, expired gas 28 mmHg CO2?

A

Vd/Vt = 0.33

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22
Q

What does Vd/Vt = 0 mean?

A
  • no physiologic dead space

- expired PeCO2 = arterial PaCO2

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23
Q

What does Vd/Vt = 1 mean?

A
  • physiologic dead space = tidal volume

- expired PeCO2 is zero so there is no gas exchange occuring

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24
Q

What is minute ventilation?

A

Tidal volume [vol/breath] * RR [ breath/min]

Ve = Vt * RR

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25
Q

What is normal tidal volume?

A

500 mL

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26
Q

What is normal respiratory rate?

A

12-14 breaths/minute

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27
Q

What is normal minute ventilation?

A

0.450 L * 14/min = 6.3 L/min

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28
Q

What are two equations for Ve [minute ventilation]?

A

Ve = TV * RR

Ve = Vd [dead space ventilation] + V[A] [alveolar ventilation]

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29
Q

What are two equations for alveolar ventilation?

A

V[A] = (Vt - Vd)*RR

alveolar V = (tidal vol - dead space ventilation) * respiratory rate

V[A] = VCO2 * K / PACO2

alveolar V = rate of CO2 production * constant / alveolar PCO2

K = 863 mmHg for conditions of BTPS

30
Q

What is the value of the constant in the equation V[A] = VCO2 * K / alveolar PCO2?

A

K = 863 mmHg for conditions of BTPS

31
Q

What is equation for predicting alveolar PCO2?

A

VCO2 * 863 mmHg / Va

VCO2 = rate of CO2 production
VA = alveolar ventilation
32
Q

What kind of relationship is there between alveolar ventilation [VA] and alveolar PCO2 when rate of CO2 production is constant?

A

inverse relationship

VA = VCO2 * K / PACO2

33
Q

What is BTPS?

A

body temp 310 K
ambient pressure 760 mmHg
saturated water vapor

34
Q

If VCO2 is constant, what determines PACO2?

A

VA = alveolar ventilation

VCO2 = rate of CO2 production

35
Q

What happens to VA when VCO2 is doubled in order to maintain PACO2?

A

VA is doubled to maintain normal value of PACO2

36
Q

When VA is doubled, what happens to PACO2?

A

PACO2 is halved

37
Q

What is the relationship between P[A]O2 and P[A]CO2? The equation?

A

P[A]O2 = PIO2 - PACO2/R

P[A]O2 = alveolar PO2
PIO2 = inhaled PO2
P[A]CO2 = alveolar PCO2
R = respiratory exchange ratio = CO2 production/O2 consumption
38
Q

What is the respiratory exchange ratio [R]?

A

R = CO2 production / O2 consumption

39
Q

What is normal level for respiratory exchange ratio [R]?

40
Q

What happens to PACO2 and PAO2 if alveolar ventilation is halved?

A

PACO2 is doubled

PAO2 is more than halved

41
Q

Are variations in PO2 or PCO2 higher between inspired air and mixed venous blood?

A

much greater variation in PO2

42
Q

What are two things that vary among different regions of heart due to gravitational effects?

A
  • regional blood flow [Q]

- alveolar ventilation [VA]

43
Q

Where does FRC mostly reside in lung?

A

apex of lung

44
Q

Where is ventilation highest?

A

the base of lung

– because most potential space exists in base since apex is full with FRC

45
Q

Where is Q [blood flow] highest in lung?

46
Q

Where is V/Q highest vs lowest in lung?

A

lowest V/Q in bottom of lung

highest V/Q in top of lung

47
Q

What is normal V/Q?

48
Q

What is normal alveolar ventilation VA?

A

4 LPM [liters per minute] [4-4.8 to be exact]

49
Q

What is normal lung perfusion [C.O.]?

A

5 LPM [5-6 to be exact]

50
Q

What is normal PAO2?

51
Q

What is normal PACO2?

52
Q

When is V/Q = infinity?

A

when ventilation without perfusion = dead space

53
Q

When is V/Q = 0?

A

when perfusion without ventilation = shunt

54
Q

Are regional differences in ventilation or perfusion greater?

A

regional differences in perfusion are greater

55
Q

What is ratio at base?

ventilation at base? blood flow? PaO2? PaCO2?

A 
ratio = 0.5
PaO2 = 89 mmHg
PaCo2 = 42 mmHg

ventilation = 0.82
blood flow = 1.29

56
Q

What is ratio at apex?

ventilation at apex? blood flow? PaO2? PaCO2?

A 
ratio = 3.0
PaO2 = 130 mmHg
PaCO2 = 28 mmHg

ventilation = 0.24
blood flow = 0.07

57
Q

Where is V/Q ratio highest? lowest?

A

highest in zone 1 = apex

lowest in zone 3 = base

58
Q

Where is PaO2 highest? lowest?

A

highest in zone 1 = apex

lowest in zone 3 = base

59
Q

Where is PaCO2 highest? lowest?

A

highest in zone 3 = base

lowest in zone 1 = apex

60
Q

What are PaCO2 and PaO2 in pulmonary veins?

A 
PaCO2 = 40 mmHg
PaO2 = 100 mmHg
61
Q

What is PaO2 and PaCO2 in pulmonary embolus / dead space?

A 
PAO2 = 150 mmHg
PACO2 = 0 mmHg
62
Q

What is PAO2 and PACO2 in shunt/ airway obstruction / right to left cardiac shunt? What about PO2 and PCO2 in venous blood? V/Q?

A 
PAO2 = none
PACO2 = none
- since no air flow
PO2 venous = 40
PCO2 venous = 46

V/Q = 0

63
Q

What happens when high V/Q? What happens to PO2 and PCO2 in pulmonary capillary blood?

A

high ventilation relative to perfusion

blood has high PO2, low CO2

64
Q

What happens when low V/Q? what happens to PO2 and PCO2 in pulmonary capillary bed? example of when this happens?

A
  • low ventilation relative to perfusion –> due to deficient ventilation or excessive perfusion
  • blood has low O2, high CO2
  • asthma attack
65
Q

What happens to V/Q in pulmonary embolism?

A

V/Q = infinity

66
Q

What happens to V/Q in airway obstruction?

67
Q

What happens to V/Q in right to left cardiac shunt?

68
Q

What happens to V/Q in asthma attack

69
Q

What is normal atm PO2 and PCO2?

A 
PO2 = 150 mmHg
PCO2 = 0
70
Q

What is normal PO2 and PCO2 in pulm artery [aka before gas exchange]?

A 
O2 = 40
CO2 = 45

Physiology Part 2 (19 decks)

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