Pulm/Renal - Physiology - Pulmonary Ventilation; Diffusion; Blood Flow; Metabolism; V-Q Relationships Flashcards Preview

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Flashcards in Pulm/Renal - Physiology - Pulmonary Ventilation; Diffusion; Blood Flow; Metabolism; V-Q Relationships Deck (123)
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1
Q

Describe some of the functions of the lungs and respiratory system.

A

(1) To transport / warm / humidify / filter air for gas exchange

(2) To filter the blood for particles, clots, or tumors

(3) To metabolize compounds (e.g. peptides, amines, arachidonic acid metabolites)

(4) To provide a reservoir for blood for the left ventricle

(5) To facilitate speech / vocalization

2
Q

In what organ system is angiotensin I converted to angiotensin II?

In what organ system is bradykinin removed from the blood?

A

The lungs;

the lungs

3
Q

How thick is the alveolar-capillary membrane?

A

0.3 μm

4
Q

True/False.

Large increases in pulmonary capillary pressure can damage the thin alveolar-capillary interface (0.3 μm).

A

True.

5
Q

Identify the labeled structures in this scanning electron micrograph.

A
6
Q

What structures will an O2 molecule in the alveolar air cross to reach a passing RBC and bind to hemoglobin?

A

A surfactant layer –>

A type I pneumocyte –>

The pneumocyte basement membrane –>

The interstitial space –>

The capillary basement membrane –>

The capillary endothelial cell –>

Plasma –>

The RBC membrane –>

Hemoglobin

7
Q

True/False.

Fibroblasts impair gas exchange in the alveoli.

A

True.

(due to fibrosis and increased collagen / fiber deposition)

8
Q

Describe the epithelium type of a type I and type II pneumocyte.

A

Type I - simple squamous (less abundant but make up 95% of surface area)

Type II - simple cuboidal (more abundant)

9
Q

Which section of the respiratory system has the smallest cross-sectional area?

Which section of the respiratory system has the largest cross-sectional area?

A

The smallest bronchi;

the alveoli

10
Q

How much volume (on average) is in the conducting zone?

How much volume (on average) is in the alveoli?

A

150 mL

(~1 mL per lb. ideal body weight)

2 - 3 L

11
Q

Which zone of the respiratory tract is synonymous with dead space?

How much volume is typically in this space?

A

The conducting zone;

150 mL

(~1 mL per lb. ideal body weight)

12
Q

What is the purpose of nasal turbinates?

A

To increase surface area and warm/humidify the air

13
Q

What is Dalton’s law?

(In relation to atmospheric pressure)

A

Total gas pressure = the sum of the partial pressures of its constituent gasses

(e.g. Patm = pH2O +pCO2 + pO2 + pN2)

14
Q

What gas partial pressures contribute to atmospheric air pressure (Patm)?

A

pH2O +pCO2 + pO2 + pN2

15
Q

What is Henry’s law?

(In relation to atmospheric pressure)

A

The amount of gas dissolved is proportional to its partial pressure

(e.g. Pgas = Fgas x Patm)

16
Q

What is the partial pressure of oxygen in inspired air (dry, ambient, and at sea level)?

A

150 mmHg

  • (PO2 * (Patm - PH2O))*
  • (0.21 * (760 - 47))*
17
Q

What is the partial pressure of H2O in dry, ambient air at seal level that has just been inhaled into the nose?

What will the partial pressure be by the time it has passed through the trachea?

A

0 mmHg;

47 mmHg

18
Q

Describe the changes in partial pressure of O2 as air travels from the environment through the nose, trachea, and alveoli.

(Note: assume dry, ambient air at sea level.)

A
19
Q

Describe the changes in partial pressure of CO2 as air travels from the environment through the nose, trachea, and alveoli.

(Note: assume dry, ambient air at sea level.)

A
20
Q

Describe the changes in partial pressure of H2O as air travels from the environment through the nose, trachea, and alveoli.

(Note: assume dry, ambient air at sea level.)

A
21
Q

What is the water pressure in dry, sea level air that has been inspired, humidified, and warmed?

A

47 mmHg

22
Q

How long does blood normally remain in contact with the pulmonary capillaries before moving on (assume at rest and not in a disease state)?

A

0.75 seconds

23
Q

When does surfactant production begin in utero?

A

~25 weeks

24
Q

Which alveoli will collapse first in cases of surfactant deficiency, the small or the large?

A

The small

(Due to the law of LaPlace, the pressure in the small is greater and so they flow into the large. Surfactant is meant to counter this pressure differential.)

25
Q

After ingesting foreign particles, what do alveolar macrophages usually do next?

A

Travel either:

(1) out the mucociliary escalator to be swallowed and digested,
(2) to bronchial lymph nodes for antigen presentation

26
Q

Identify each of these lung volumes.

(From top to bottom for each column)

A

Column 1: IRV, TV, ERV, RV

Column 2: IC, FRC

Column 3: VC

Column 4: TLC

27
Q

What is an average tidal volume?

What is an average total lung capacity?

A

500 mL;

6 L

28
Q

The inspiratory capacity (usually ~3 L)

+

the _______________________

=

total lung capacity.

A

Functional residual capacity

(usually ~3 L)

29
Q

How much is the average inspiratory capacity?

How much is the average expiratory reserve volume?

How much is the average residual volume?

A

3 L;

  1. 5 L;
  2. 5 L
30
Q

How is total ventilation calculated?

How is alveolar ventilation calculated?

A

Tidal volume * respiratory rate

(e.g. 500 mL * 15 breaths/min)

(Tidal volume - dead space) * respiratory rate

(e.g. (500 mL - 150 mL) * 15 breaths/min)

31
Q

What effect will cutting a patient’s respiration rate in half have on their blood pCO2​?

A

It will ~double

32
Q

Which organ system has primary control over CO2 levels in the blood?

A

The lungs

33
Q

What is alveolar dead space?

A

The air that makes it into non-perfused alveoli

(e.g. at the very top of the lungs)

34
Q

What is anatomic dead space?

What is alveolar dead space?

What is physiologic dead space?

A

The conducting zone (~150 mL);

non-perfused alveoli;

the anatomic DS + the alveolar DS

35
Q

What effect does lung disease have on physiological dead space?

A

An increase

36
Q

Where does more ventilation occur, the lower or upper lung?

Why?

A

The lower

(gravity effects + lower alveoli are smaller and expand more)

37
Q

Where does more perfusion occur, the lower or upper lung?

A

The lower lung

38
Q

Describe gas movement in the respiratory system using the terms ‘bulk flow’ and ‘diffusion.’

A

Bulk flow is the collective movement of gas into the body and down the trachea;

diffusion is the alveolar-arterial movement of individual gasses due to partial pressures down their concentration gradient from otherwise stationary collective gas

39
Q

Do bulk flow pressures push oxygen into the arteries?

A

No, diffusion down partial pressure gradients

40
Q

Which diffuses more easily through biological membranes, CO2 or O2?

A

CO2

41
Q

Explain, according to Fick’s law, what factors are proportional to the diffusion rate across the alverolar-arterial membrane.

Explain, according to Fick’s law, what factors are inversely proportional to the diffusion rate across the alverolar-arterial membrane.

A

Cross-sectional area (A), partial pressure difference (P1 - P2)

Thickness (T)

42
Q

Which ‘a’ is which in the A-a gradient?

A

Big A = alveolar partial pressure (PA)

Little a = arterial partial pressure (Pa)

43
Q

What gas is diffusion limited?

What does this mean for its alveolar-arterial differences in partial pressure?

A

Carbon monoxide (CO);

its arterial pressure (Pa) will always be lower than its alveolar pressure (PA)

44
Q

What gas is used for measuring DLCO?

Why?

What is this measurement?

A

Carbon monoxide,

it is diffusion-limited;

diffusion capacity

45
Q

Is nitrous oxide (N2O) diffusion- or perfusion-limited? Will it equilibrate quickly or slowly?

Is carbon monoxide (CO) diffusion- or perfusion-limited? Will it equilibrate quickly or slowly?

Is oxygen (O2) diffusion- or perfusion-limited? Will it equilibrate quickly or slowly?

A

Perfusion; quickly.

Diffusion; it never does.

Perfusion; quickly.

46
Q

True/False.

Transfer of O2 into the blood is always a perfusion-limited process.

A

False.

It becomes diffusion-limited under abnormal circumstances.

47
Q

What is Fick’s law?

A
48
Q

What effect will a decreased hematocrit have on a patient’s diffusion capacity (DL) in the lungs?

A

It will decrease

(because there is less Hgb for O2 to bind, less O2 gets through)

49
Q

How much oxygen is carried by 1 g of hemoglobin?

A

1.34 mL

50
Q

How can the oxygen content of the blood be calculated?

A

(1.34 mL * Hgb * (oxyHgb - Hgb)/100) + 0.003(pO2)

51
Q

How many mL of O2 are dissolved in one dL of blood?

How many mL of O2 are bound to one g/dL of Hgb?

A
  1. 3
    * (0.003 for each mm of air pressure)*
  2. 34
    * (Takeaway: much more bound than dissolved)*
52
Q

What is the usual value for parteryO2? And pveinO2?

What is the usual value for parteryCO2? And pveinCO2?

A

PaO2: 90 mmHg; PvO2: 40 mmHg

PaCO2: 40 mmHg; PvCO2: 45 mmHg

53
Q

Under normal conditions, which of the following (or both or neither) are perfusion-limited, O2 or CO2​?

Under abnormal conditions, which of the following (or both or neither) are diffusion-limited, O2 or CO2?

A

Both;

both

54
Q

Describe the pressures within the pulmonary and bronchial arterial systems, respectively.

A

Pulmonary arteries: low pressure, high compliance system

25/8 mmHg

Bronchial arteries: normal, systemic pressures

120/80 mmHg

55
Q

What equation can be used to calculate pulmonary vascular resistance?

A

Ohm’s Law: R = (Input pressure - output pressure) / blood flow

(R = V / I)

56
Q

The pressure drop across pulmonary circulation is about 10 mmHg. Blood flow is about 6 L/min.

What is the pulmonary vascular resistance?

A
  1. 7 mmHg/L
    * (Input pressure - output pressure) / blood flow = 10 / 6*
57
Q

What will happen to pulmonary vascular resistance if cardiac output increases?

A

It will decrease

(V = IR; if I increases, R must decrease to maintain V)

58
Q

Via what two structural mechanisms can pulmonary vascular resistance be decreased?

A

Recruitment;

vessel distention

59
Q

Describe the effects of lung volume on pulmonary vascular resistance.

At what point is the PVR lowest?

A

See image.

The functional reserve capacity.

60
Q

Which lung volume cannot be directly measured?

A

Residual volume

61
Q

Name a few examples of substances/factors that increase pulmonary vascular tone, thus increasing resistance.

A

Histamine

Hypoxia

Norepinephrine

Endothelin

Serotonin

62
Q

Name a few examples of substances/factors that decrease pulmonary vascular tone, thus decreasing resistance.

A

Acetylcholine

Phosphodiesterse inhibitors

Prostacyclin (PGI2)

Ca2+ channel blockers

63
Q

What are the two organs in which phosphodiesterase inhibitors function? What is the effect?

What are some example drugs in this class?

A

The lungs and penis –> smooth muscle relaxation;

sildenafil, vardenafil

64
Q

What test can be used to see if pulmonary hypertension is being caused by left-sided heart failure or by pulmonary disease?

A

Get the ‘wedge’ pressure (left ventricular filling pressure)

via a Swan-Ganz catheter

65
Q

Describe the differences in pressures in West Zone 1.

A

PAlveolus > PArtery > PVein

66
Q

Describe the differences in pressures in West Zone 2.

A

PArtery > PAlveolus > PVein

67
Q

Describe the differences in pressures in West Zone 3.

A

PArtery > PVein > PAlveolus

68
Q

In which West Zone is there no pulmonary blood flow?

What are two examples of situations that might increase the size of this zone?

A

West Zone 1;

hemorrhage, positive pressure ventilation

69
Q

Describe where West Zones 1, 2, and 3 are, respectively, in the lungs.

A
70
Q

Are there any capillary beds in the body that respond to hypoxemia by vasoconstricting?

A

Yes;

the pulmonary capillary beds

(pulmonary hypoxic vasoconstriction)

71
Q

What about high altitudes can cause pulmonary hypertension?

A

Widespread hypoxic vasoconstriction

72
Q

How does hypoxic vasoconstriction factor into birth and newborn respiration?

A

Before birth: the infant’s pulmonary arterioles are uniformly vasoconstricted.

At first breath: the hypoxic vasoconstriction is reversed by the incoming oxygen, and the alveoli all pop open.

73
Q

What is the point of hypoxic pulmonary vasoconstriction?

A

To shunt blood to more oxygen-rich alveoli

74
Q

What are some basic causes of pulmonary edema?

A

Pulmonary hypertension

Infection (i.e. pneumonia)

Nephrotic syndrome (loss of oncotic pressure)

Liver failure (loss of oncotic pressure)

75
Q

What other primary function does ACE have besides converting angiotensin I to angiotensin II?

A

Inactivating bradykinin

76
Q

Name a few substances that are inactivated in the lungs.

A

Serotonin

Bradykinin

Prostaglandins E1, E2, and F2α

77
Q

True/False.

IgE is secreted into the respiratory mucus and mucopolysaccharides are secreted into the bronchial mucus.

A

False.

IgA is secreted into the respiratory mucus and mucopolysaccharides are secreted into the bronchial mucus.

78
Q

What role do the lungs play in serotonin management?

What role do the lungs play in heparin management?

A

Inactivation and storage;

production via mast cells

79
Q

1. How is the partial pressure of oxygen in the trachea (pO2) calculated?

2. How is the partial pressure of oxygen in an alveolus (pAO2) calculated?

A

1. 0.21 * (760 - 47) = 150 mmHg

2. Now, just subtract out the pCO2 (~40 mmHg) –>

150 mmHg - pCO2/0.8

(~100 mmHg)

80
Q

In the equation for alveolar partial pressure of oxygen (pAO2 = pIO2 - pCO2/R), what value do we give to the constant, R?

A

0.8

81
Q

Why do pAlveolarO2 levels drop in cases of hypoventilation?

A

The pCO2 rises

(remember Dalton and Henrys’ laws)

82
Q
A

D.

83
Q

What are the four physiologic causes of hypoxemia?

A
  1. Hypoventilation
  2. Diffusion limitation
  3. Shunt
  4. V/Q mismatch
84
Q

What effect does hypoventilation have on arterial and alveolar pCO2?

A

Both increase

85
Q

What are some example causes of hypoventilation?

A

Drugs: e.g. alcohol, benzodiazepenes, opiates, etc.

Morbid obesity, airway obstruction

Nerve conduction diseases: e.g. myasthenia gravis

Spinal cord damage

Chest wall damage

Paralysis

86
Q

Describe the effect (increase or decrease) of each of the following on the paO2:

Hypoventilation

Diffusion limitation

Shunt

V/Q mismatch

A

Decrease

Decrease

Decrease

Decrease

87
Q

What is a shunt?

A

Any case where blood traverses the lungs without being ventilated

88
Q

What effect does an increase in the fraction of inspired O2 (FiO2) have on a shunt?

A

Very little

(the shunt bypasses the air, so changes in O2 are irrelevant)

89
Q

Explain the shunt fraction equation (attached).

A

Qs = Blood flow through shunt

QT = Total blood flow past alveolus

Cc’O2 = Ideal blood oxygen levels (if all extracted at 1.34 mL per dL)

CaO2 = measured arterial pO2

CaO2 = measured pO2​ after mixing of shunt and non-shunt blood

90
Q

Why is the shunt fraction equation (attached) useful?

A

It allows for determining what proportion of pulmonary blood flow is being shunted

91
Q

True/False.

Supplemental oxygen can be used to treat the effects of hypoventilation but not usually those of a shunt.

A

True.

92
Q

Which is essentially a shunt, a V/Q of infinity or a V/Q of 0?

A

V/Q of 0

(ventilation blocked)

93
Q

What is a normal V/Q relationship?

Does it increase or decrease from West Zone 1 to 2 to 3?

A

1:1

Decrease (perfusion increasing)

94
Q
A

B.

95
Q

A patient’s pCO2 is 80 mmHg (normal 40 mmHg). What is their pAO2?

What percentage supplemental oxygen (FiO2) do you need to give to get them back to 100 mmHg pAO2?

A

pAO2 = FiO2 - pCO2/R = 150 - 80/0.8 = 50 mmHg

pAO2 = FiO2 - pCO2/R

100 = (x)(760-47) - 80/0.8

x = 0.28

28%

96
Q

What effect will a V/Q mismatch approaching 0 have on arterial and venous CO2/O2 levels?

Normal:

Arterial O2 — 90 mmHg

Arterial CO2 — 40 mmHg

Venous O2 — 40 mmHg

Venous CO2 — 45 mmHg

A

Arterial O2 — 40 mmHg

Arterial CO2 — 40 mmHg

Venous O2 — 45 mmHg

Venous CO2 — 45 mmHg

97
Q

What effect will a V/Q mismatch approaching infinity have on alveolar O2 and CO2 levels?

Normal:

Alveolar O2 — 90 mmHg

Alveolar CO2 — 40 mmHg

A

Alveolar O2 — 150 mmHg

Alveolar CO2 — 0 mmHg

(no more CO2 driving down the O2:CO2 ratio)

98
Q

Identify which V/Q mismatch is a shunt and which is dead space:

Increasing V/Q (from normal)

Decreasing V/Q (from normal)

A

Increasing — Dead space

(virtually no blood flow –> cannot be a shunt)

Decreasing — Shunt

(i.e. blood flowing past blocked alveoli)

99
Q

Is the V/Q relationship higher or lower than 1 at the top of the lung?

Is the V/Q relationship higher or lower than 1 at the bottom of the lung?

A

Higher;

lower

100
Q

Explain why tuberculosis favors the upper lobes of the lungs. Use V/Q relationship terminology.

A

The upper portions of the lung have a higher V/Q relationship than the lower lobes. TB loves O2.

Higher V/Q –> more ventilation than blood flow –> less CO2 to blow off and more ventilation to do it –> the fraction of O2 in the alveolus increases as CO2 decreases (maybe even approaching 150 mmHg pO2 and 0 mmHg pCO2)

101
Q

Does ventilation change much from the top to the bottom of the lungs?

Does perfusion change much from the top to the bottom of the lungs?

A

A little, not much (it increases).

Yes (it increases drastically).

102
Q

A higher V/Q relationship leads to a(n) ____________ in CO2 and a(n) ______________ in O2. (Increase/Decrease)

A lower V/Q relationship leads to a(n) ____________ in CO2 and a(n) ______________ in O2. (Increase/Decrease)

A

Decrease, increase;

increase, decrease

103
Q
A

B.

104
Q

True/False.

The blood passing through the pulmonary arteries has a higher O2 content than mixed venous blood.

A

False.

It is mixed venous blood (i.e. the blood returning to the heart from all the organs pooled together. I.e. what is found in the vena cava.).

105
Q

What would it mean for V/Q to equal 3.3 at the top of the lungs?

What would it mean for V/Q to equal 0.63 at the bottom of the lungs?

A

Relatively more ventilation than perfusion

Relatively more perfusion than ventilation

106
Q

Will blood pH be lower at the top or the bottom of the lungs?

A

The bottom

(due to the decreased V/Q)

107
Q

When will paO2 be higher than pAO2?

A

Never!

Arterial pO2 is a function of alveolar pO2 and is always slightly less.

(Hence, the A-a gradient is always positive.)

108
Q

Given paO2 in an arterial blood gas (ABG) reading, what else do you need to calculate the A-a gradient?

A

Just pAO2 (alveolar pO2)

pAO2 = PiO2 - pCO2/R

109
Q

A normal A-a gradient should be:

A

< age/4 + 4

OR

< age/3

(both methods work)

110
Q

What is the patient’s A-a gradient?

What does this indicate about the patient’s condition?

A

25 (normal for his age: ~16);

the hypoxemia is not due to hypoventilation (otherwise, the A-a gradient would have been normal)

111
Q

How can you differentiate between a patient’s shunt or another V/Q mismatch?

A

Give 100% O2.

If the paO2 improves, it’s not a shunt.

112
Q

Describe the changes in capillary bed engorgement/stretching/perfusion/recruitment in the top of the lungs vs. the bottom of the lungs.

A
113
Q

How many alveoli are in the body?

A

~500,000,000

114
Q

Surfactant is especially important in keeping the _______ (small/large) alveoli patent.

A

Small

(remember the law of LaPlace)

115
Q

What are the three measurement categories that are typically taken in a pulmonary function testing lab?

A
  1. Spirometry (rate + volumes)
  2. Lung volumes (static)
  3. Diffusion capacity (DLCO)
116
Q

What is another name for total ventilation?

Is this the same as alveolar ventilation?

A

Minute ventilation;

no

117
Q

Will a 2000 mL breath have a larger dead space, as opposed to the 150 mL of dead space in a normal tidal volume of 500 mL?

A

No, the dead space volume remains constant

118
Q

True/False.

A wedge pressure is measured using a Swan-Ganz catheter which temporarily occludes a portion of the lung (using a balloon) and measures the right ventricular filling pressure on the proximal portion of the occlusion.

A

False.

A wedge pressure is measured using a Swan-Ganz catheter which temporarily occludes a portion of the lung (using a balloon) and measures the left* ventricular filling pressure on the *distal portion of the occlusion.

119
Q

What is a normal left ventricular filling pressure?

How can this be measured?

A

< 12 mmHg (pulmonary edema occurs at ≥ 18);

a Swan-Ganz catheter

120
Q

Blood that flows through the lungs without being oxygenated is known as:

A

Shunt.

121
Q

True/False.

The paCO2 and pACO2 can be assumed to be virtually identical.

A

True.

122
Q

What is the typical V/Q at the very top of the lungs?

What is the typical V/Q at the very bottom of the lungs?

A

~3;

~0.7

123
Q

Why is there a higher oxygen tension at the top of the lungs vs. the bottom?

A

The V/Q relationship is higher at the top

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