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STEP 1 (1) > Respiratory-Physiology > Flashcards

Respiratory-Physiology Flashcards

1
Q
A
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2
Q

What is inspiratory reserve volume?

A

air that can still be inspired after normal tidal inspiration

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3
Q

What is tidal volume?

A

Air that moves into the lung with each quiet inspiration, normally 500 mL

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4
Q

What is exspiratory reserve volume?

A

air that can still be breathed out after normal expiration

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5
Q

What is residual volume?

A

The total amount of air remaining in the lung after maximal expiration (cannot be measured on spirometry)

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6
Q

What is inspiratory capacity?

A

IRV +TV

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7
Q

What is functional residual capacity?

A

RV + ERV (cannot be measured on spirometry because it includes residual volume)

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8
Q

What is vital capacity?

A

TV + IRV + ERV, or the maximum volume of gas that can be expired after a maximal inspiration

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9
Q

What is total lung capacity?

A

IRV + TV + ERV+ RV (cannot be measured on spirometry)

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10
Q

What is physiologic dead spead?

A

Vd= the anatomic dead space of conducting airways plus alveolar dead space, or the volume of inspired air that does not participate in gas exchange

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11
Q

What is the eqn for physiologic dead space?

A

Vd= Vt *((PaCo2- PECo2)/PaCo2), where

Vt= tidal volume

PaCo2= arterial Co2

PeCo2= expired air Co2

Taco Paco Peco Paco

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12
Q

What part of the lung is the largest contributor of alveolar dead space?

A

the apex

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13
Q

What is the eqn for minute ventilation?

A

total volume of gas entering the lungs per minute

Ve= Vt*RR

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14
Q

What is the eqn for alveolar ventilation?

A

Volume of the gas per unit time that reaches the alveoli

Va= (Vt-Vd)*RR

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15
Q

What is a normal physiological dead space volume?

A

150 mL/breath

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16
Q

Compliance increases in what kinds of lung disease?

A

obstructive, such as emphysema, and in normal aging

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17
Q

Compliance decreases in what kinds of lung disease?

A

Restrictive disease, such as Pulmonary fibrosis, pneumonia, and pulmonary edema

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18
Q

What is hysteresis?

A

the fact the the lung inflation curve is different than that of the deflation curve due to the need to overcome surfac tension to expand

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19
Q

What is the structure of hemoglobin?

A

4 polypeptide subunits, 2 alpha, and 2 beta

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20
Q

What are the conformations of hemoglobin?

A

T (taut) and R (relaxed)

Taut near tissue and

Relaxed near respiratory areas

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21
Q

What are some characteristics of taut hemoglobin?

A

This form has LOW affinity for O2, thus promoting release/unloading of oxygen (whereas hemoglobin in a relaxed form would be more likely to hold onto oxygen)

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22
Q

What things promote a taut orientation of hemoglobin?

A

increased Cl-, CO2, H+ (acidotic), 2-3-BPG, and increased temp all favor a RIGHT SHIFT of the dissociation curve for increased o2 unloading

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23
Q

What is the composition of fetal hemoglobin?

A

2a and 2y subunits that have HIGHER affinity for O2 than adult Hb, driving duffion of oxygen across the palcenta to the fetus

NOTE: a higher affinity for O2 moves the fetal oxygen-hemoglobin dissociation curve to the LEFT

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24
Q

What is methemoglobin?

A

A modified form of hemoglobin in which the central iron is in a ferric (Fe3+) state that does NOT bind O2 as readily, but has increased affinity for cyanide

NOTE: Iron in normal hemoglobin is an Fe2+ state

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25
Q

How might someone with methemoglobemia present?

A

cyanosis and chocolate-colored blood

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26
Q

How can methemoglobinemia be treated?

A

methylene blue and vitamin C

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27
Q

What are some things that cause methemoglobinemia?

A

nitrates and benzocaine

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28
Q

How can methemoglobinemia be used medically to our advantage?

A

It can be medically induced using nitrrites followed by thiosulfate to treat cyanide poisoning

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29
Q

How would carboxyhemoglobin be treated?

30
Q

Describe these curves

A

Hemoglobin has a sigmodial curve due to positive cooperativity of O2 binding by successive hemoglobin subunits, while myoglobin does not exhibit this property

31
Q

What happens when the oxygen-hemoglobin dissociation curve shifts to the right?

A

There is decreased affinity of Hb for O2, which facilitates easier unloading of O2 into tissue

32
Q

What things cause a right shift of the oxygen-hemoglobin dissociation curve?

A

Right shift: ACE BATs right

Acid

Co2

Exercise

2,3-BPG

Altitude

Temperature

33
Q

Which shift, right or left, of the oxygen-hemoglobin dissociation curve would cause increased EPO synthesis?

A

left because O2 is not being unloaded as easily leading to hypoxia

34
Q

What is the eqn for the oxygen content of blood?

A

(1.34*Hb*SaO2) + (0.003*PaO2)

Hb= hemoglobin levels

SaO2= arterial O2 saturation

35
Q

T or F. With decreased hemoglobin, there is decreased O2 content of blood but no change in O2 saturation and PaO2

36
Q

What is the eqn for O2 delivery to tissue?

A

CO x O2 content of blood

37
Q

How does CO poisoning affect Hb concentration? SaO2? PaO2? Total O2 content?

A

Hb concentration- normal

SaO2- decreased

PaO2- normal

Total O2 content- decreased

38
Q

How does anemia affect Hb concentration? SaO2? PaO2? Total O2 content?

A

Hb concentration- decreased

SaO2- normal

PaO2- normal

Total O2 content- decreased

39
Q

How does polycythemia affect Hb concentration? SaO2? PaO2? Total O2 content?

A

Hb concentration- increased

SaO2- normal

PaO2-normal

Total O2 content- increased

40
Q

How does hypoxia affect the pulmonary circulation?

A

Normally it is a low-resistance, high-compliance system but in the absence of adequate oxygen, hypoxic vasoconstriction occurs that helps shift blood away from poorly ventilated regions

41
Q

What are some situations of gas exchange that are perfusion limited?

A

O2 in normal states, CO2, N2O

In these states, diffusion can only be increased if blood flow increases

42
Q

What are some situations of gas exchange that are diffusion limited?

A

emphysema and fibrosis, CO

In these states, gas does not equilibrate by the time blood reaches the end of a capillary

43
Q

What is the eqn for diffusion of a gas?

A

Diffusion= A*Dk*(P1-P2)/T, where

A= area

Dk(P1-P2)= difference in partial pressure

T= thickness of wall

44
Q

What variable of the gas exchange eqn is changed in emphysema?

A

A is decreases

45
Q

What variable of the gas exchange eqn is changed in pulmonary fibrosis?

A

T is increased

46
Q

What is the eqn for pukmonary vascular resistance?

A

PVR= (Ppulm a.- Pleft atrium)/CO

47
Q

What is the eqn for alveolar gas exchange?

A

pAO2= PIo2- PaCO2/R, where

pA02= alveolar O2

PaCO2= arterial Co2

R= respiratory quotient, or Co2 produced at tissue/O2 consumed

48
Q

Normal alveolar gas eqn.

A

PAO2= 150- PaCo2/0.8

49
Q

What is the A-a gradient?

A

PAo2- PaO2

Normal= ~10 mm Hg

50
Q

What things can make an A-a gradient increase?

A

hypoxia caused by shunting, V/Q mismatch, and fibrosis

51
Q

What is hypoxia?

A

decreases O2 delivery to tissue

52
Q

What are some causes of hypoxia?

A

decreased CO, anemia, CO poisoning, and hypoxemia

53
Q

What is hypoxemia?

A

decreased PaO2

54
Q

What are some causes of hypoxemia with a NORMAL A-a gradient?

A

high altitude and hypoventilation (i.e. overdose)

55
Q

What are some causes of hypoxemia with an INCREASED A-a gradient?

A

V/Q mismatch, Diffusion limitation (fibrosis), Right-to-left shunt

56
Q

What are the V/Q ratios in different parts of the lung?

A

Apex= 3 (wasted ventilation)

Base= 0.6 (wasted blood flow/perfusion)

57
Q

T or F. Both ventilation and perfusion are greater at the base of the lung compared to the apex

58
Q

What happens to the V/Q ratio with exercise?

A

vasodilation of apical capillaries occurs, and the V/Q ratio approaches 1

59
Q

What kinds of organisms would thrive in the apex of the lung?

A

Aerobes like TB

60
Q

A V/Q of/near zero suggests what?

A

airway obstruction (shunt). I.e. foreign body aspiration

In a shunt, 100% O2 WILL NOT improve PaO2

61
Q

A V/Q of/near infinity suggests what?

A

blood flow obstruction (i.e. pulmonary embolism)

In this case 100 O2 WILL improve PaO2

62
Q

What are the pressure ratios in the apex of the lung?

A

PA > Pa > Pv

63
Q

What are the pressure ratios in the middle of the lung?

A

Pa > PA > Pv

64
Q

What are the pressure ratios in the base of the lung?

A

Pa > Pv > PA

65
Q

How is Co2 transported from tissue?

A

3 forms:

as HCO3- (90%)

carbaminohemoglobin (5%)

Dissolved CO2 (5%)

66
Q

Describe venous transport of Co2 via carbaminohemoglobin

A

In this case Co2 is bound to Hb at the N-terminus of globin (not heme).

67
Q

How is Co2 converted to HCO3?

A

. CO2 released from tissue enters RBCs where carbonic anhydrase converts it to H2CO3, which then dissociates to H+ and HCO3-. HCO3- leaves the cell in exchange for Cl-

68
Q

Study more about Haldane, Bohr, and other effects of Co2, O2 exchnage in hemoglobin

69
Q

How does the body respond to high altitude?

A

decreased PiO2 leads to decreased PaO2 leading to increased ventilation, pushing off more PaCO2 leading to a short state of respiratory alkalosis. The kidneys then respond by pushing off HCo3-

Study more from pulm

70
Q

How else does the body react to altitude?

A

EPO increases and 2,3-BPG also increases to improve O2 unloading at tissues due to the hypoxia

The lungs respond to hypoxia by vasoconstricting which can lead to pulmonary hypertension

71
Q

How do the lungs respond to exercise?

A

CO2 production increases, as does O2 consumption, leading to ventilation increasing and V/Q ratios throughout the lung becoming more uniform

72
Q

How do PaO2 and PaCo2 change in exercise?

A

They dont, but there is an increase in venous Co2 content and a decrease in venous O2 content

STEP 1 (1) (28 decks)

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