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αναπνευστικο f > fisiologia > Flashcards

fisiologia Flashcards

1
Q

What is the term for the volume of air in excess of tidal volume that moves into the lung on inspiration?

A

Inspiratory reserve volume

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2
Q

A man breathes calmly and quietly. He takes in a normal breath and then lets it out without any forcing. What volume of air is being moved?

A

Tidal volume, which is approximately 500 mL

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3
Q

What is the term for the volume of air that can still be breathed out after a normal expiration?

A

Expiratory reserve volume

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4
Q

What is the term for the volume of air in the lungs after maximal expiration?

A

Residual volume

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5
Q

What is unmeasurable on spirometry: inspiratory reserve volume, tidal volume, expiratory reserve volume, residual volume?

A

Residual volume

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6
Q

The inspiratory reserve volume plus the tidal volume equals what?

A

Inspiratory capacity

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7
Q

The residual volume plus the expiratory reserve volume equals what?

A

The functional reserve capacity

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8
Q

Describe the functional reserve capacity. What are its two components?

A

FRC = the total volume left in the lungs after normal expiration; residual volume + expiratory reserve volume = FRC

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9
Q

Vital capacity equals the sum of what three lung volumes?

A

Tidal volume, inspiratory reserve volume, and expiratory reserve volume

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10
Q

What is the term for the maximum volume of air that can be inhaled and exhaled?

A

Vital capacity

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11
Q

A patient exhales as much as he can, inhales as much as he can, and then exhales as much as he can again. What volume of air has he moved?

A

His vital capacity (VC)

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12
Q

Inspiratory reserve volume plus tidal volume plus expiratory reserve volume plus residual volume equals what?

A

Total lung capacity

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13
Q

Name the four lung volumes.

A

Lung volumes (LITER) = Inspiratory reserve (IRV), Tidal (TV), Expiratory reserve (ERV), Residual (RV)

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14
Q

What is the definition of a capacity?

A

The sum of greater than or equal to two physiologic volumes

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15
Q

What is the equation for determining the volume of dead space in the lungs, where PaCO2 = arterial and PECO2 = expired air?

A

VD = VT × ([PaCO2 - PECO2]/PaCO2) (Taco, Paco, PEco, Paco, as the order of variables)

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16
Q

You know a patient’s physiologic dead space, expired air CO2, and arterial CO2. Can you calculate their tidal volume (VT)?

A

Yes, as VD = VT × ([PaCO2 - PECO2]/PaCO2), where PaCO2 = arterial, and PECO2 = expired air

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17
Q

A patient’s tidal volume is 500 mL, PaCO2 is 50 mmHg, and PECO2 is 35 mmHg. What is the physiologic dead space?

A

150 mL; VD = 500 mL × ([50 mmHg - 35 mmHg]/50 mmHg)

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18
Q

Describe the parts of the airway that contribute to the physiologic dead space.

A

Conducting airways that contribute to anatomic dead space, and alveolar dead space

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19
Q

Which alveolar section of the healthy lung contributes more to physiologic dead space: the apex or the base?

A

Apex

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20
Q

What is the volume of inspired air that does not contribute to gas exchange?

A

Physiologic dead space, VD

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21
Q

What is minute ventilation (VE)? How do you calculate it?

A

The total volume of gas entering the lungs each minute; VE = VT × respiratory rate

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22
Q

A patient with a tidal volume of 400 mL is breathing 20 times per minute. What is his minute ventilation?

A

8000 mL/min, as minute ventilation (VE) = 400 mL × 20 breaths/min

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23
Q

What is alveolar ventilation (VA)? How do you calculate it?

A

The volume of gas per unit time that reaches the alveoli; VA = (VT - VD) × respiratory rate

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24
Q

A patient with a tidal volume of 650 mL is breathing 10 times per minute. His dead space is 150 mL. What is his alveolar ventilation?

A

5000 mL/min, as alveolar ventilation (VA) = (650 mL - 150 mL) × 10 breaths/min

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25
Q

A patient is breathing naturally. Describe the natural tendency of movement of the lung and chest wall.

A

The lungs tend to collapse inward, and chest wall springs outward

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26
Q

At what point in the respiratory cycle is the inward pull of the lung equal to the outward pull of the chest wall?

A

At functional residual capacity

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27
Q

At the point of functional residual capacity, what is the value of the air pressure within the lungs?

A

At FRC, the pressure within the lungs is equal to atmospheric pressure

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28
Q

A patient takes in a deep breath. What determines the combined volume of the chest wall and lungs?

A

Elastic properties of both

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29
Q

• In terms of lung pressures, explain how a pneumothorax is prevented.

A

At FRC, lung pressures are atmospheric, and opposing forces of the lung and chest wall create negative pressure in the intrapleural space

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30
Q

• When is pulmonary vascular resistance at a minimum?

A

At functional residual capacity

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31
Q

What is compliance?

A

The change in lung volume for a given change in pressure

32
Q

• A 43-y/o woman has pulmonary fibrosis. How does this affect her lung compliance? Other conditions that would affect compliance similarly?

A

Lung compliance decreases with pulmonary fibrosis, and in pulmonary edema and pneumonia

33
Q

Lung compliance ____ (increases/decreases) in a patient with emphysema, and with natural aging.

A

Increases

34
Q

• How many polypeptide subunits make up hemoglobin?

A

Four

35
Q

What are the two conformational forms of hemoglobin?

A

Relaxed (oxygenated) and taut (deoxygenated)

36
Q

Of the two forms of hemoglobin, the taut (T) form has ____ (high/low) affinity for oxygen. The relaxed (R) form has ____ (high/low) affinity.

A

Low; high (300 times more affinity in R form) (Taut in Tissues, Relaxed in Respiratory tract)

37
Q

Does hemoglobin have positive or negative cooperativity with respect to oxygen binding and affinity?

A

Positive

38
Q

Does hemoglobin have positive or negative allostery with respect to oxygen binding and affinity?

A

Negative

39
Q

An increase in which five factors will favor the taut form of hemoglobin over the relaxed form and will decrease affinity for oxygen?

A

Chloride (Cl-), protons (H+), carbon dioxide, 2,3-bisphosphoglycerate, and temperature

40
Q

A patient is exercising in the freezing cold. He is otherwise healthy. Is his hemoglobin more likely to be taut or relaxed?

A

Taut, as exercise (generating CO2) favors the taut form (the outside temperatures are meaningless, as body temperature is what matters)

41
Q

Fetal hemoglobin has ____ (higher/lower) affinity for 2,3-BPG than does adult hemoglobin, causing ____ a (higher/lower) affinity for oxygen.

A

Lower, higher

42
Q

Hemoglobin can act as a buffer for which ions?

A

H+

43
Q

Changes to hemoglobin can lead to decreased O2 ____ and ____, causing hypoxia in tissues.

A

• Saturation, content

44
Q

Normal Hb iron is ____(reduced/oxidized), or ____(ferric/ferrous). Methemoglobin iron is ____(reduced/oxidized), or ____(ferric/ferrous).

A

Reduced, ferrous (just the 2 of us: ferrous is Fe2+); oxidized, ferric (Fe3+)

45
Q

A man suffers from cyanide poisoning. What property of methemoglobin makes it useful for treatment?

A

The ferric (Fe3+) state of methemoglobin decreases the affinity for O2 but increases the affinity for cyanide

46
Q

A cyanotic patient is found to have chocolate-colored blood. Treatment?

A

Methylene blue (this patient has methemoglobinemia)

47
Q

• A child has cyanide poisoning. What is the mechanism of action of nitrites used in the treatment?

A

Nitrites oxidize iron to form methemoglobin, which readily binds cyanide, restoring function to cytochrome oxidase

48
Q

A patient has cyanide poisoning. What two treatments do you give?

A

Nitrites and subsequently thiosulfate

49
Q

A patient looks blue and has blood that has turned brown. What caused this?

A

Poisoning by nitrites or benzocaine

50
Q

What is the name of a form of hemoglobin in which carbon monoxide is bound instead of oxygen?

A

Carboxyhemoglobin

51
Q

When another molecule, such as carbon monoxide, binds to hemoglobin in place of oxygen, what are the systemic effects?

A

CO causes a left shift in the oxygen-hemoglobin curve, resulting in tissue hypoxia from decreased oxygen unloading

52
Q

Does carbon monoxide or oxygen have a greater affinity for hemoglobin?

A

CO has 200 times the affinity of oxygen for hemoglobin

53
Q

What is the shape of the oxygen-hemoglobin dissociation curve? Explain.

A

Sigmoidal due to positive cooperativity, as Hb can bind four O2 molecules—O2 binding is easier when more O2 is bound

54
Q

How does the structure of myoglobin affect its function?

A

It is monomeric and thus has no positive cooperativity as seen in hemoglobin, and it lacks the sigmoidal curve

55
Q

When the oxygen-hemoglobin dissociation curve shifts to the right, what happens to the affinity of hemoglobin for oxygen?

A

A right shift decreases the affinity of hemoglobin for oxygen

56
Q

When the oxygen-hemoglobin dissociation curve shifts to the right, what happens to the O2 saturation (%) at a PO2 of 50 mmHg?

A

• A right shift decreases oxygen saturation (higher oxygen pressure is required to saturate hemoglobin)

57
Q

A shift of the oxygen-hemoglobin dissociation curve to the right facilitates what process in tissue?

A

The unloading of oxygen to tissue

58
Q

When the oxygen-hemoglobin dissociation curve shifts to the left, what happens to the affinity of hemoglobin for oxygen?

A

A left shift increases the affinity of hemoglobin for oxygen

59
Q

Increases in the amount of which six factors cause a right shift of the oxygen-hemoglobin dissociation curve?

A

Right = ACE BATs right handed (Acid [H+], CO2, Exercise, 2,3-BPG, Altitude, Temperature)

60
Q

When the oxygen-hemoglobin dissociation curve shifts to the left, what happens to the O2 saturation (%) at a PO2 of 50 mmHg?

A

A left shift increases oxygen saturation (less oxygen pressure is required to saturate hemoglobin)

61
Q

Decreases in the amount of which factors cause a left shift of the oxygen-hemoglobin dissociation curve?

A

Acid (H+), CO2, exercise, 2,3-BPG, altitude, temperature

62
Q

A fetus’s oxygen-hemoglobin dissociation curve is investigated. How does it compare to an adult’s oxygen-hemoglobin dissociation curve?

A

It is shifted to the left (fetal hemoglobin has higher affinity for oxygen than has adult hemoglobin)

63
Q

A patient in shock develops a lactic acidosis. This decrease in pH causes what kind of shift in the oxygen-hemoglobin dissociation curve?

A

Right shift (due to increased acid [or H+] lowering the pH)

64
Q

A patient’s chest is injured and her partial pressure of CO2 is increased. How does this affect her oxygen-hemoglobin dissociation curve?

A

Shifts it to the right

65
Q

A patient is exercising. What effect would this have on his oxygen-hemoglobin dissociation curve?

A

• A right shift

66
Q

An increase in 2,3-bisphosphoglycerate (2,3-BPG) causes a ____ (left/right) shift in the oxygen-hemoglobin dissociation curve.

A

Right

67
Q

A hiker scales an extremely tall mountain. High altitude induces what change in the oxygen-hemoglobin dissociation curve?

A

A right shift

68
Q

A patient develops a fever. An increase in temperature causes what kind of shift in the oxygen-hemoglobin dissociation curve?

A

A right shift

69
Q

What is the equation for oxygen content in the blood?

A

O2 content = (O2 binding capacity × percent saturation) + dissolved O2

70
Q

What is the normal level of hemoglobin in the blood. How many milliliters of oxygen can it bind?

A

Normal Hb amount = 15 g/dL; each gram can bind 1.34 mL of oxygen

71
Q

A previously healthy patient develops blue lips and fingertips. What does this say about the value of her deoxygenated hemoglobin level?

A

Her deoxygenated hemoglobin must be >5 g/dL (this is cyanosis)

72
Q

What is the normal value of the O2 binding capacity?

A

• 20.1 mL O2/dL

73
Q

As Hb falls, what happens to each parameter (increase/decrease/unchanged): O2 content of arterial blood, O2 saturation, arterial PO2?

A

O2 content of arterial blood decreases, O2 saturation and arterial PO2 remain unchanged

74
Q

How do you calculate oxygen delivery to the tissues?

A

O2 delivery to tissues = cardiac output × O2 content of blood

75
Q

A woman has CO poisoning. What are the likely levels of her Hb, %O2 saturation of Hb, dissolved O2 (PaO22 content?

A

• Hb is normal, %O2 saturation of Hb is decreased (CO competes with O2), PaO2 is normal, and total O2 content is decreased

76
Q

A woman has fatigue and pallor. What are the likely levels of her Hb, %O2 saturation of Hb, dissolved O2 (PaO2), and total O2 content?

A

Hb is decreased, %O2 saturation of Hb is normal, PaO2 is normal, and total O2 content is decreased (she has anemia)

77
Q

A man has polycythemia. What are the likely levels of his Hb, %O2 saturation of Hb, dissolved O2 (PaO2), and total O2 content?

A

Hb is increased, %O2 saturation of Hb is normal, PaO2 is normal, and total O2 is content increased

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