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Physiology > Respiratory Physiology Lecture 2 > Flashcards

Respiratory Physiology Lecture 2 Flashcards

1
Q

What does Boyle’s Law state?

A

The pressure and volume of a gas are inversely related

P1*V1 = P2*V2

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2
Q

A decrease in PIP causes the lungs to ______

A

expand

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3
Q

What does Henry’s Law state?

A

The amount of gas that dissolves into a fluid is related to:

  1. solubility of the gas into that fluid
  2. Temperature of the fluid
  3. Partial pressure of the gas
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4
Q

What does Dalton’s Law state?

A

The total pressure of a gas mixture is equal to the sum of the pressures that each gas exerts independently

Ex: PB = PO2 + PN2……

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5
Q

What are normal atmospheric pressure (PB) as well as partial pressures of N2 (PN2) and O2 (PO2)?

A

PB: 760 mm Hg

PN2: 600 mm Hg (~79%)

PO2: 160 mm Hg (~21%)

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6
Q

PO2 = ?

A

PO2 = PB * FO2

(FO2 = fraction of O2)

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7
Q

What happens to PB, PO2, and FO2 when elevation increases? Why?

A

PB: decreases

PO2: decreases

FO2: no change

Gravity is decreased at higher elevations, which causes pressures to decrease.

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8
Q

What is the purpose of your lungs diluting gas with water vapor during inspiration?

A

Keeps alveoli moist; Decrease PO2 without changing the percentage of O2

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9
Q

VE = ?

A

VE = VT * f

VE = total ventilation (mL/min)

VT = tidal volume (mL/breath)

f = respiratory rate or frequency (breaths/min)

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10
Q

What is a normal total ventilation at rest?

A

~6000 mL/min

500 mL/breath * 12 breaths/min

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11
Q

What are the two types of dead space? How are they different?

A

Anatomical dead space: in conducting airways (~150 mL) prior to alveoli

Alveolar dead space: alveoli with poor circulation (varies); lethal in diseased lungs

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12
Q

VA = ?

A

VA = (VT - VD) * f

VA = alveolar ventilation (more important than VE)

VT = tidal volume

VD = anatomic dead space

f = respiratory rate

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13
Q

What is a normal alveolar ventilation?

A

~4200 mL/min

(500 mL/breath - 150 mL) * 12 breaths/min

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14
Q

What happens to alveolar ventilation during shallow, rapid breathing?

A

Decreases drastically (“wasted ventilation”)

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15
Q

What is the best way to increase alveolar ventilation?

A

By increasing tidal volume

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16
Q

What is PaCO2?

A

Partial pressure of CO2 in arterial blood

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17
Q

What happens to PaCO2 during hyperventilation (increase VA)?

A

Decreases

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18
Q

What happens to PaCO2 during hypoventilation (VA decreases)?

A

Increases

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19
Q

Changing VA is the mechanism for regulating _____? (2)

A

PaCO2

pH

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20
Q

What are some reasons as to why VA would not be adequate to overcome high PaCO2? (2)

A

Not enough ventilation (CNS depression or respiratory muscle weakness)

Too much ventilation ending up as dead space ventilation (COPD or rapid, shallow breathing)

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21
Q

If PaCO2 is > 45 mmHg, what happens to the blood and alveolar ventilation?

A

Blood: Hypercapnia

VA: Hypoventilation

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22
Q

If PaCO2 is 35-45 mmHg, what happens to the blood and alveolar ventilation?

A

Blood: eucapnia

VA: normal

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23
Q

If PaCO2 is < 35 mmHg, what happens to the blood and alveolar ventilation?

A

Blood: hypocapnia

Alveolar ventilation: hyperventilation

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24
Q

What is the alveolar gas equation?

A

Measures partial pressure of a gas in an alveolus

Ex: PAO2 = PIO2 - PACO2 / R

PIO2 = PO2 in

PACO2 = PO2 leaving alveoli

R = ratio of CO2 to O2 exchanged in alveoli (assume 0.8)

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25
Q

What is PO2 under the following conditions?

Ambient air (dry)

Moist tracheal air

Alveolar gas (R = 0.8)

Systemic arterial blood

Mixed venous blood

A

Ambient air (dry): 159 mmHg

Moist tracheal air: 150 mmHg

Alveolar gas (R = 0.8): 102 mmHg

Systemic arterial blood: 90 mmHg

Mixed venous blood: 40 mmHg

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26
Q

What is PCO2 for the following conditions:

Ambient air (dry)

Moist tracheal air

Alveolar gas (R = 0.8)

Systemic arterial blood

Mixed venous blood

A

Ambient air (dry): 0 mmHg

Moist tracheal air: 0 mmHg

Alveolar gas (R = 0.8): 40 mmHg

Systemic arterial blood: 40 mmHg

Mixed venous blood: 46 mmHg

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27
Q

Why does PACO2 = PaCO2?

A

CO2 has a high diffusibility

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28
Q

What are the two circulations that the lungs receive? What do they do?

A

Pulmonary circulation: perfuse alveoli for gas exchange; arises from RV; receives 100% of RV output

Bronchial circulation: meet the needs of the lung (similar to coronaries for the heart); arises from aorta; 2% of LV output

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29
Q

Pulmonary blood flow has _____ flow and _____ pressure.

A

High flow (5 L/min)

Low pressure (25/8 mmHg)

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30
Q

What factors contribute to a very compliant, low resistance pulmonary circulation which relies on a weak pump (RV)? (4)

A

Pulmonary arteries are shorter and more dilated

Pulmonary arterioles are thin-walled (less smooth muscle & tone)

More distensible (7x more compliant)

Enormous number of capillaries, in unique arrangement to create sheets of blood flow past alveoli (resistors in parallel)

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31
Q

What three factors alter pulmonary vascular resistance?

A

Changes in blood flow (perfusion)

Changes in lung volume

Changes in local O2 concentrations

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32
Q

What happens to pulmonary blood flow and resistance during times of increased cardiac output (exercise)?

A

Increased pulmonary blood flow

Decreased resistance

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33
Q

What happens to pulmonary blood flow and resistance during times of low cardiac output (heart failure)?

A

Decreased pulmonary blood flow

Increased resistance

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34
Q

How is resistance decreased at high lung volumes?

A

PIP becomes more negative

Transmural pressure increases

Distended extra-alveolar vessels

Resistance decreases

35
Q

How is resistance increased at high lung volumes?

A

Alveolar diameter increases, crushing alveolar vessels

36
Q

How is resistance increased at low lung volumes?

A

PIP becomes more positive

compresses extra-alveolar vessels

increases resistance

37
Q

How is resistance decreased at low lung volumes?

A

Alveolar diameter decreases

38
Q

What is the difference between hypoxia and hypoxemia? What do they trigger?

A

Hypoxia: low O2 in alveoli

Hypoxemia: low O2 in blood

Both trigger vasoconstriction of the pulmonary circulation and vasodilation systemically

39
Q

What are the differences between regional and generalized hypoxia?

A

Regional: vasoconstriction localized to specific regions of the lungs; often caused by bronchial obstruction

Generalized: vasoconstriction throughout both lungs; caused by high altitudes and chronic hypoxia (asthma, emphysema, etc)

40
Q

Which factor has the greatest effect on regional distribution of blood flow in the lungs?

Pulmonary circulation

Gravity

41
Q

In an upright person, blood flow in the lungs is highest near _____ and lowest near _____

A

Highest: near base

Lowest: near apex

42
Q

Every 1 cm above the heart, hydrostatic pressure decreases _____?

43
Q

What three pressure affect pulmonary blood flow and help differentiate lung zones (1, 2, and 3)?

A

Alveolar (PA)

Venous (PV)

Arterial (Pa)

44
Q

Describe zone 1 of the lungs. How is it created?

A

Apex

Occurs when PA > Pa (positive pressure ventilation or hemorrhage)

Usually small/nonexistent in healthy people

45
Q

Describe zone 2 of the lungs. What are the differences in pressure for Pa, PA, and PV?

A

Middle 1/3 of the lung

Pa > PA > PV

46
Q

Which zone of the lungs is the primary area of distension and recruitment of vessels during exercise?

47
Q

What are the pressure differences between PV, PA, and Pa in zone 3 of the lungs?

A

Pa > PV > PA

48
Q

What is the optimal ventilation/perfusion (V/Q) ratio for gas exchange?

49
Q

What are the two types of gas movement in the lungs? How are they different from each other?

A

Bulk flow: how gas moves in airways from trachea to alveoli; mass movement like water out of a faucet; occurs when there are differences in total pressure

Diffusion: how gas moves in us from air –> liquid; liquid –> air; gases move due to their individual pressure gradients

50
Q

Gas diffusion is determined by what two factors?

A

Diffusion properties of a membrane (Fick’s Law)

Pulmonary capillary blood flow

51
Q

What does Fick’s Law state? Which variable is the biggest determinant of rate of diffusion?

A

Vgas α (A * D * (P1-P2)/T)

A = surface area

D = diffusion constant of a specific gas

P1-P2 (biggest determinant) = partial pressure difference of the gas on each side of the tissue

T = tissue thickness

Vgas is directly related to numerator; inversely related to T

52
Q

How many Hb molecules are there in one red blood cell?

A

280 million

53
Q

The amount of HbO2 is a function of _____ in blood.

54
Q

When blood PO2 is high in the pulmonary capillaries, _____.

A

forms HbO2 (increased % saturation)

55
Q

When blood PO2 is low in systemic capillaries, _____.

A

O2 is released from Hb (decreased % saturation)

56
Q

SO2 = ?

A

SO2 = (HbO2 content/HbO2 capacity) * 100

SO2: % saturation of Hb with O2

HbO2: oxyhemoglobin

57
Q

Does binding of O2 to each heme group increase or decrease the affinity of Hb for O2?

58
Q

What does it mean when the oxyhemoglobin dissociation curve “shifts right”? What factors can cause this? (Hint: CADET face right)

A

Decrease in Hb’s affinity for O2; aids in release/unloading of O2

CO2

Acidity

2,3 diphosphoglycerate (end product in RBC metabolism)

Temperature

59
Q

What does it mean when the oxyhemoglobin dissociation curve “shifts left”?

A

Increase in Hb’s affinity for O2; aids in uptake/binding of O2

60
Q

Carbon monoxide (CO) shifts the oxyhemoglobin curve ______. Why?

A

Left

CO and O2 compete for the same Hb binding site, but CO has a 240x greater affinity than O2

61
Q

How is CO2 transported in the blood? (3)

A

As bicarbonate ions (60%)

Physically dissolved (10%)

Chemically bound to Hb (30%)

62
Q

Total CO2 content in arterial blood is ______.

A

59 mL CO2/100 mL blood

63
Q

Total O2 content in arterial blood is ______.

A

19.7 mL O2/100 mL blood

64
Q

What does CaO2 represent? How is it calculated?

A

The total number of O2 molecules in arterial blood, both bound and unbound to Hb

CaO2 = (Hb (g/dL) * 1.34 mL O2/g Hb *SaO2) + (PaO2 * (0.003 mL O2/mmHg/dL))

  1. 34 mL/g Hb: fully saturated Hb
  2. 003 mL O2/mmHg/dL: how much O2 can be dissolved for each mmHg of pressure at body temperature
65
Q

On one visit, a patient has a PaO2 of 85 mmHg, an SaO2 of 98%, and a Hb of 14 g/dL. One year later her hemoglobin is 7 g/dL. Assuming no lung disease, what will be her new PaO2, SaO2, and CaO2?

A

PaO2 unchanged

SaO2 unchanged

CaO2 reduced

66
Q

Which patient is more hypoxemic (total O2)?

A: PaO2 85 mmHg, SaO2 95%, Hb 7 g/dL

B: PaO2 55mmHg, SaO2 85%, Hb 15 g/dL

67
Q

How do the effects of gravity on the upright lung affect the following at the apex:

Blood flow

Ventilation

V/Q ratio

PaO2

PaCO2

A

Drastically decreases blood flow

Decreases ventilation (overventilated)

Increased V/Q ratio

Increased PaO2

Decreased PaCO2

68
Q

How do the effects of gravity on the upright lung affect the following at the base:

Blood flow

Ventilation

V/Q ratio

PaO2

PaCO2

A

Drastically increases blood flow (overperfused)

Increases ventilation

Decreases V/Q ratio

Drastically decreased PaO2 (blood not fully oxygenated)

Increased PaO2

69
Q

What is the Alveolar-arterial O2 difference (A-a gradient) and what is it used for? What is the equation for it? What is a normal value for it?

A

Measure of gas exchange efficiency across alveolar-capillary membrane; used to determine cause of hypoxemia

P(A-a)O2 = [(PB-H2O) * (FIO2) - PaCO2/R] - PO2

*FIO2 = fraction of O2 in

≤ 20mmHg

70
Q

What are the five causes of hypoxemia? What must PaO2 be in order to be considered hypoxemic?

A
  1. Hypoventilation
  2. Low inspired O2
  3. Right-to-left shunt (deoxy blood bypasses lungs)
  4. V/Q mismatch (emphysema)
  5. Diffusion impairment

PaO2 < 80 mmHg

71
Q

In hypoxemia, how is A-aO2 difference affected under each of the five causes?

Hypoventilation

Low inspired O2

R-L shunt

V/Q mismatch

Diffusion impairment

A

Hypoventilation: no change

Low inspired O2: no change

R-L shunt: increase

V/Q mismatch: increase

Diffusion impairment: increase

72
Q

In hypoxemia, how is FIO2 affected under each of the five causes?

Hypoventilation

Low inspired O2

R-L shunt

V/Q mismatch

Diffusion impairment

A

Hypoventilation: increases

Low inspired O2: increases

R-L shunt: no change

V/Q mismatch: increases

Diffusion impairment: increases

73
Q

What are the three components of the ventilatory system? What are they each responsible for?

A

Sensors (chemoreceptors & mechanoreceptors) = feedback

Central controller (respiratory control center) = the driver

Effectors (respiratory muscles) = carry out the orders

74
Q

What are the components of the respiratory control center (2)?

A

Medullary Centers

Pontine centers

75
Q

What are the two components of the medullary center? What are their functions?

A

Dorsal respiratory group (DRG): comprised mainly of inspiratory neurons

Ventral respiratory group (VRG): responsible for inspiration and expiration, but inactive during quiet breathing

*major rhythm generator*

76
Q

What is the pre-botzinger complex?

A

Anatomical location of the respiratory pattern generator; display pacemaker activity; located superior to the ventral respiratory group

77
Q

What are the two components of the pontine center? What are their functions? Which component dominates over the other?

A

Modulate rhythms generated in the medulla

Pneumotaxic center: terminates inspiration (increases rate of breathing because limiting inspiration shortens expiration)

Apneustic center: prevents inspiratory neurons from being shut off; prolongs inspiration

Apneustic center dominates

78
Q

Describe central chemoreceptors. Where are they located? What is their function?

A

Located on the surface of the medulla; separate from respiratory center; responsible for 80% of the total ventilatory response

Sensitive to pH (PaCO2); most important mechanism controlling ventilation at rest (CO2-induced H+ in CSF)

The reason why we can’t hold our breath beyond ~1 minute

79
Q

Describe peripheral chemoreceptors. Where are they located? What conditions do they respond to?

A

Glomus cells in the carotid and aortic bodies

Responds to hypoxia (PaO2) by inhibition of K+ channels

Responds to hypercapnia when CO2 diffuses into glomus as bicarbonate, H+ inhibits K+ channels

Responds to acidosis when H+ inhibits K+ channels

responds to all by signaling to medulla to increase ventilation

80
Q

What are pulmonary stretch receptors? What do they respond to?

A

Mechanoreceptors in smooth muscle of conducting airways

Respond to lung distension (excites inspiratory off switch; shortens inspiration when VT is large)

81
Q

What are joint and muscle receptors? Function?

A

Mechanoreceptors in joints and muscle that signal DRG to increase breathing frequency

Activated during movement, when O2 demand is or will be high (feed-forward mechanism with exercise)

82
Q

What are irritant receptors? Location? Function?

A

Mechanoreceptors in airway epithelium of larger conducting airways

Respond to irritation of the airways by touch, dust, smoke, etc

Protects by inducing a cough and hyperpnea

Physiology (11 decks)

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