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Physiology #4 > RESP 4 > Flashcards

RESP 4 Flashcards

1
Q

What is the % of hemoglobin saturated with O2 in the pulmonary veins (SvO2)?

A

75%

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2
Q

What is the % of hemoglobin saturated with O2 in the pulmonary arteries (SaO2)?

A

97%

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3
Q

___ of O2 reversibly binds to
hemoglobin inside of the RBC

A

98%

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4
Q

___ of total oxygen content is
dissolved in plasma

A

2%

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5
Q

Iron must be in __________ state to bind O2

A

ferrous (Fe2+)

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6
Q

The amount of oxygen bound to Hb depends on:

A
  1. Plasma PO2
  2. Number of binding sites in RBCs depends on the Hb amount per RBC
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7
Q

What is CaO2?

A

ml of O2carried by oxyhemoglobin plus ml of O2 carried dissolved in plasma

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8
Q

What is the average CaO2?

A

19.782 ml O2/ 100 ml blood

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9
Q

What is positive cooperativity?

A

At a high PO2, hemoglobin’s affinity for O2 is highest.

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10
Q

The lower the PO2, the ____ likely O2 will dissociate from hemoglobin.

A

more

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11
Q

2,3-BPG binds to Beta subunits of deoxy HB and ________ its O2 affinity

A

decreases

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12
Q

What is the bohr effect?

A

Oxyhemoglobin Dissociation Curve Shifts to the RIGHT

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13
Q

What does a right shift in the Oxyhemoglobin Dissociation Curve cause?

A
  • DECREASED affinity between hemoglobin and oxygen
  • oxygen is MORE likely to dissociate
    from Hemoglobin.
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14
Q

When do levels of 2,3-BPG increase?

A
  • exercise
  • hypoxia from high altitude
  • pregnancy
  • chronic lung disease
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15
Q

What causes a right shift in the Oxyhemoglobin Dissociation Curve?

A
  • increased hydrogen ions (lower pH)
  • increased CO2
  • increased temperature
  • increased BPG
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16
Q

What does a left shift in the Oxyhemoglobin Dissociation Curve cause?

A
  • INCREASED affinity between oxygen and hemoglobin
  • oxygen is LESS likely to dissociate from hemoglobin
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17
Q

What causes a left shift in the Oxyhemoglobin Dissociation Curve?

A

– Decreased PCO2
– Increased pH
– Decreased temperature
– Decreased 2,3-BPG

18
Q

Carbon Monoxide has a ______ greater affinity for Hemoglobin than Oxygen.

A

250X

19
Q

CO bound to hemoglobin _______ Hb’s affinity for O2.

A

increases
- left-ward shift

20
Q

What is the treatment for carbon monoxide poisoning?

A
  • Pure oxygen
  • 5% CO2
21
Q

What are the variants of hemoglobin?

A
  1. Methemoglobin
  2. Hemoglobin F (fetal hemoglobin)
  3. Hemoglobin S (sickle cell)
22
Q

How does fetal hemoglobin differ from HbA?

A
  • left shift
  • no B chains
  • higher affinity for oxygen
23
Q

How is methemoglobin different from HbA?

A
  • Heme with Fe3+ does not bind O2 as readily (reduced
    affinity)
  • Causes any heme groups in the same Hb molecule with heme in the Fe2+ state to have have higher affinity for bound O2 ➔ net effect is reduced O2 delivery to the tissues
24
Q

What causes methemoglobin to form?

A
  • Ferrous to ferric
  • occur due to G6PDH deficiency or upon exposure to some local anesthetics
25
Q

How does hemoglobin S (sickle cell) differ from HbA?

A

– Normal α units, abnormal B units
– When deoxygenated, RBCs form sickle shapes, obstructing small vessels
– O2 has lower affinity

26
Q

What are the causes of hypoxemia?

A
  • decreased FiO2
  • hypoventilation
  • diffusion defects
  • V/Q defects
27
Q

What is wrong with the A-a gradient in each of these causes of hypoxemia?

A
  • decreased FiO2 = normal gradient
  • hypoventilation = normal gradient
  • diffusion defects = increased gradient
  • V/Q defects = increased gradient
28
Q

How does PaO2 change in all of the causes of hypoxemia?

A

decreased PaO2

29
Q

What are the three ways carbon dioxide is transported in the blood?

A
  1. Dissolved CO2
  2. Carbamino-hemoglobin (CO2Hgb)
  3. Bicarbonate (HCO3-)
30
Q

What is the main way of CO2 transport?

A

bicarb

31
Q

What is the bicarb equation?

A
32
Q

What is the haldane effect in systemic capillaries?

A

Deoxygenated Hb promotes increased binding of CO2 to Hb.

33
Q

What is the haldane effect in the pulmonary capillaries?

A

Oxygenated Hb promotes dissociation of CO2 from Hb.

34
Q

Which way does CO2 move in the systemic capillaries?

A
  • tissue
  • capillary walls
  • plasma
  • erythrocyte
35
Q

Which way does CO2 move in the pulmonary capillaries?

A
  • erythrocyte
  • plasma
  • capillary wall
  • alveolus
36
Q

What are the causes of methemoglobinemia?

A
  • acquired (exposure to chemicals that cause oxidative stress)
  • inherited (deficiency in NADH-MetHb reductase)
37
Q

How can you treat acquired Methemoglobinemia?

A

methylene blue and dextrose infusion
- cofactor for the NADPH-MetHb Reductase Pathway, but this is contraindicated in patients with G6PD deficiency

38
Q

How does methylene blue stop oxidative stress and methemoglobinemia?

A

uses NADPH to create for HbFe2+ instead of 3+

39
Q

The only way RBCs make NADPH is
through a pathway catalyzed by what pathway?

A

Glucose 6-Phosphate Dehydrogenase (G6PD)

40
Q

If someone has a Glucose 6-Phosphate Dehydrogenase deficiency what will methylene blue cause?

A

more damage since it is an oxidant that can lead to hemolysis

Physiology #4 (11 decks)

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