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SF3 - Test 2 > 1 - O2 and CO2 Transport by Blood ( I ) > Flashcards

1 - O2 and CO2 Transport by Blood ( I ) Flashcards

1
Q

Objectives: Explain oxygen transport

Storage?

Left vs Right Shifts of Equilibrium?

Purpose of Hb?

A
  • Gasses move down partial pressure gradients
  • Stored:
    • ​Physically Dissolved in the Plasma
      • 0.3 ml O2/100 ml = 3 ml O2/L
    • (Majority) Bound to Hemoglobin (Hb)
      • Does NOT contribute to partial pressure
  • Equilibrium:
    • Left: Unloading O2 @ tissue
      • Decrease PO2
      • Low PO2 (all Hb-O2) shifts equation left
    • Right: Loading O2 @ lungs
      • Increase PO2
      • High PO2 (all dissolved in blood, none on Hb) shifts equation right
  • Hb acts a buffer for oxygen, it has a very low solubility in blood alone
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2
Q

Objectives: Explain carbon dioxide transport

Tissue?

Lungs?

A
  • Gasses move down partial pressure gradients
  • Essentially follows opposite of O2
  • Tissue:
    • CO2 accumulates at metabolizing tissues
    • Majority diffuses into blood as bicarbonate
    • Transported via venous circulation to lungs
  • Lungs:
    • CO2 converted back to gas and released via expiration
    • Carbonic Anhydrase key enzyme for
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3
Q

Objectives: Explain the interactions of oxygen and carbon dioxide transport

A
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4
Q

Objectives: Recognize diseases affecting oxygen transport

Anemia

Carbon Monoxide (CO)

A
  • Anemia: Low RBC count = Low Hb Content
    • ​Arterial blood lower % Volume @ 100 mmHg
    • Venous blood (-5%) will be at lower PO2 (mmHg)
      • ​Tissue O2 lower than normal
  • Carbon Monoxide (CO)
    • ​Occupies O2 binding site
    • PaCO = 0 mmHg (always bound!)
    • Raises remaining O2 affinity; will not unload unless very low O2 in tissues
    • Cherry Red Skin Appearance
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5
Q

Henry’s Law and Solubility

A
  • Decribes partial pressure of gasses in fluids
  • The amount of gas dissolved in fluids depends on solubility coefficients and partial pressures
    • ​Gasses moved fown partial pressure gradient, NOT a concentration gradient
  • O2 = 0.003 ml/100 ml blood/mmHg
  • CO2 = 0.06 ml/100 ml blood/mmHg (20x O2)
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6
Q

What is the influence of gasses on partial pressures once they have undergone chemical reactions? (e.g. Hb-O2, HCO3)

A

They no longer exert partial pressure

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7
Q

If the amount of gas dissolved doubles, what occurs to the partial pressure?

A

It doubles

Remember–dissolved gas = partial pressure!

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8
Q

What is the chemical equation for eqilibrium of Hb and Oxygen?

How do the following conditions affect it?

High Alt

Breathing 100% Oxygen

Breating High-P (hyperbaric) 100% oxygen

Hypoxic Conidtions

A

4 O2 (gas) + Hb <–> Hb(O2)4

  • High Alt: Decreased PPO2 , left shift
  • Breathing 100% O2: Increased PPO2 , right shift
  • Hyperbaric O2: Decompression sickness; lungs gather more oxygen; right shift
  • Hypoxic Conditions: Low oxygen at tissue; left shift
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9
Q

Explain Hb binding to Oxygen

Kinetics?

Total molecules?

How does binding occur in the alveolar space?

How does unloading occur in the tissue space?

A
  • Displays saturation kinetics
  • Binds 4 O2 molecules
  • Alveolar Space:
    • ​Inspired Air + pH20 = 150mmHg O2
    • O2 diffuses into plasma, raising PO2 in plasma
    • O2 associates with Hb to form Hb(O2)4
    • Hb acts as O2 acceptor as RBCs returning to lungs have low [O2] ; oxygen flows down partial pressure gradient
  • At Tissue:
    • ​RBCs with high Hb(O2)4
    • Oxygen dissolves into plasma and diffuses down partial pressure gradient into interstitial space (tissues low in [O2]
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10
Q

How do you calculate O2 content in blood?

A
  • Two Sources:
    • O2 Content = Dissolved O2 + Hb(O2)4
    • 1 gm Hb binds 1.34 ml O2​
      • Dissolved O2 = (1.34 mL O2 x #g Hb x O2 %)
      • Hb(O2)4 = 0.3 vol % @ 100 mmHg = 0.3 mL O2 / 100 mL of blood (use for conversions as nec.)
  • Arteries vs Veins: Lose ~ 5% , Δ60 mmHg PO2
    • Need to know:
      • ml Blood (usually 100 ml)
      • g Hb / ml Blood (usually 15 g)
      • Arterial or Veinous % Oxygen
      • 0.3% volume O2 @ 100 mmHg for conv.
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11
Q

What is O2 Capacity?

Affected by: Polycythemia, Anema, CO poisoning?

A
  • Maximal amount of oxygen Hb is capable of carring
    • Does not include dissolved oxygen
  • Disease:
    • Polycythemia - High Hb - Increased
    • Anemia - Low Hb - Decreased
    • CO - Decreased
  • Equation:
    • O2 Capacity = O2 Content - O2 Dissolved
    • Hb Saturation = ( Hb-O2 / O2 Capacity ) x 100%
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12
Q

How is Hb Saturation measured?

How do the ratio of reflections compare?

How will anemia appear?

How will CO poisoning appear?

A

Pulse Oximeter

Red Light reflected by HbO2

Infra-red Light reflected by Hb

Ratio of reflection of the two wavelengths independent of absolute amount of light

Anemia will appear normal, it only tells you saturation, NOT Hb content

CO poisoning will appear normal, it only tells you saturation, NOT with what

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SF3 - Test 2 (13 decks)

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