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My Cardiopulmonary > Lecture 5B > Flashcards

Lecture 5B Flashcards

1
Q

Oxygen is carried in blood in what two forms?

A

Dissolved in plasma (1.5%)

Bound to hemoglobin (98.5%)

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2
Q

Hemoglobin increases the Oxygen carrying capacity of blood by???

A

70X

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3
Q

In hemoglobin, Iron is in what state to bind oxygen?

A

Ferrous state (Fe2+)

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4
Q

Normal adult hemoglobin is sometimes called what?

A

a2b2 (alpha 2 beta 2)

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5
Q

What 5 things in blood can influence hemoglobin saturation at a given Po2

A
  1. Temperature
  2. Blood pH
  3. Pco2
  4. BPG (2,3-bpg)
  5. DPG (2,3-dpg)
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6
Q

2,3-BPG is produced how?

A

By RBCs as they break down glucose by glycolysis. 2,3-BPG binds reversibly with hemoglobin.

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7
Q

A shift to the right in a Hemoglobin-O2 dissociation curve means what?

A
  1. Occurs when the affinity of hemoglobin for O2 is decreased.
  2. P50 is increased, and unloading of O2 from arterial blood to the tissues is facilitated
  3. For any level of Po2, the % saturation of hemoglobin is decreased
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8
Q

What 3 things Shift the dissociation curve to the right?

A
  1. Increased Pco2 or decreases in pH
  2. Increased Temperature
  3. Increased 2.3-DPG
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9
Q

The Bohr effect is associated with what factors of oxygen dissociation?

A

When the increase in Pco2 or decrease in pH decrease the affinity of hemoglobin for O2 and facilitates the unloading of O2 in the tissues.

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10
Q

When the tissues produce more Co2 for example during exercise, what happens to the pH?

A

The pH is decreased. (BOHR EFFECT)

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11
Q

How does 2,3 DPG or BPG work?

A

It binds to the beta chains of deoxyhemoglobin and decreases the affinity of hemoglobin for O2

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12
Q

Explain the relationship of chronic hypoxemia and 2,3-DPG

A

The adaptation to chronic hypoxemia (living at high altitude) includes increased synthesis of 2,3-DPG, which binds to hemoglobin and facilitates the unloading of O2 in the tissues

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13
Q

A shift to the left in the dissociation curve means what?

A
  1. Occurs when the affinity of hemoglobin for O2 is increased
  2. P50 is decreased and unloading of O2 from arterial blood into the tissues is more difficult
  3. For any level of Po2, the % saturation of hemoglobin is increased
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14
Q

What 3 things shift the dissociation curve to the left?

A
  1. Decreased Pco2 or increased pH
  2. Decreased temperature
  3. Decreased 2,3-DPG
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15
Q

T or F, Even though CO competes for O2-binding sites on hemoglobin, the affinity of hemoglobin for O2 is much greater than CO

A

False, Affinity of hemoglobin for CO is 200x its affinity for O2.

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16
Q

What happens in Carbon Monoxide Poisoning?

A
  • CO occupies O2-binding sites on hemoglobin, thus decreasing the O2 concentration of blood.
  • In addition, bind of CO to hemoglobin increases the affinity of remaining site for O2, causing a shift of the curve to the left. DRAW the CURVE
17
Q

What is Hypoxemia?

A

Decrease in arterial Po2

18
Q

WHat is Hypoxia?

A

Decreased O2 delivery to the tissues

19
Q

O2 content of blood depends on what?

A
  1. Hemoglobin concentration
  2. O2-binding capacity of hemoglobin
  3. % saturation of hemoglobin by O2
20
Q

What 3 things may cause Hypoxia?

A

Decreased Cardiac Output
Decreased O2-binding capacity of hemoglobin
Decreased arterial Po2

21
Q

What is Anemic Hypoxia?

A

Reflects poor O2 delivery resulting from too few RBCs or from RBCs that contain abnormal or too little hemoglobin

22
Q

What is Ischemic (stagnant) Hypoxia?

A

Results when blood circulation is impaired or blocked.
- Congestive heart failure may cause body-wide ischemic hypoxia, whereas emboli or thrombi block oxygen delivery only to tissues distal to the obstruction.

23
Q

What is Histotoxic Hypoxia?

A

Occurs when body cells are unable to use O2 even though adequate amounts are delivered.
- Consequence of metabolic poisons such as cyanide

24
Q

What is Hypoxemic Hypoxia?

A

Indicated by reduced arterial Po2

25
Q

What are some possible causes of Hypoxemic Hypoxia?

A

Disordered or abnormal ventilation-perfusion coupling
Pulmonary diseases that impair ventilation
Breathing air containing scant amounts of O2

26
Q

What may cause Histotoxic Hypoxia?

A

Metabolic poisons such as Cyanide

27
Q

What are the 3 forms of Carbon Dioxide in blood?

A
  1. Dissolved Co2 (small amount), which is free in solution
  2. Carbaminohemoglobin (small amount), which is CO2 bound to hemoglobin
  3. HCO3- (from hydration of CO2 in the RBCs) which is the major form (70-90%)
28
Q

What is a V/Q ratio

A

The ratio of alveolar ventilation (V) to pulmonary blood flow (Q)
- Ventilation and perfusion matching is important to achieve the ideal exchange of O2 and CO2

29
Q

What three things need to be normal for the V/Q ratio to be in its normal range

A

Frequency
Tidal Volume
Cardiac Output

30
Q

What is the normal range for V/Q ratio

A

0.8

31
Q

The V/Q ratio when at 0.8 results in what numbers for arterial Po2 and arterial Pco2?

A

Arterial Po2 –> 100mm Hg

Arterial Pco2 –> 40 mm Hg

32
Q

Within the V/Q ratio, what happens if perfusion is reduced relative to ventilation

A

Alveolar pCO2 falls because less CO2 is delivered and alveolar pO2 rises because less O2 enters the blood

33
Q

What is a shunt in respect to V/Q ratio

A

If the airways are completely blocked then ventilation is zero. If blood flow is normal, then V/Q is zero, which is called a shunt

34
Q

Is there gas exchange in a lung that is perfused but not ventilated?

A

No. V/Q makes the fraction zero.

- O2 and CO2 of pulmonary capillary blood will approach their values in mixed venous blood

35
Q

What occurs in the V/Q ratio in response to an embolism occluding a pulmonary artery?

A

If blood flow is blocked (embolism) then blood flow to that lung is zero. If ventilation is zero, then V/Q is infinite. This is called DEAD SPACE

36
Q

Is there gas exchange in a lung with no blood flow?

A

No gas exchange in a lung that is ventilated but not perfused. O2 and CO2 of alveolar gas will approach their values in inspired air. No CO2 transport

My Cardiopulmonary (17 decks)

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