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RESP > Carriage of oxygen and carbon dioxide > Flashcards

Carriage of oxygen and carbon dioxide Flashcards

1
Q

What are the sites of gas exchange in the body?

A
  • Lungs: between blood and air
  • Tissue: between blood and tissue
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2
Q

What process transfers O2 and CO2 into and out of the blood?

A
  • Diffusion
  • Pushes molecules from an area of high concentration to low concentration, until an equilibrium is reached
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3
Q

What is diffusion driven by?

A
  • Random elastic collisions between gas molecules (no energy loss)
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4
Q

Why is diffusion very fast in gas exchange?

A
  • Equilibrium is established within 1 second
  • gas molecules speed 344ms-1
  • collide 10^10 times with each other
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5
Q

What is Henry’s Law

important

A
  • States that the amount of dissolved gas in a liquid is proportional to its partial pressure in the gas form
  • C = kP
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6
Q

How is oxygen transported in the blood?

A
  • Dissolved in plasma (2%)
  • Bound to Hb (98%)
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7
Q

How does oxygen bind to haemoglobin?

A
  • Reversibly
  • 4 O2 molecules per Hb
  • 2a + 2B chains, one haem group
  • forms oxyhaemoglobin
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8
Q

What is the allosteric effect of oxygen?

A
  • After each successive binding of O2 to Hb, it’s affinity for O2 increases
  • cooperative binding
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9
Q

What is the oxygen content of blood?

A
  • total amount of O2 in blood
  • 0.3 (plasma) + 19.5 (RBC) = 19.8ml/100ml of blood
  • 20% in arterial blood, 15% in venous blood
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10
Q

What is the oxygen carrying capacity of blood?

A
  • maximum amount of O2 that can be carried by Hb
  • 1.34 (each Hb) x 15 (Hb content) = 20.1ml/100ml of blood
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11
Q

What is percentage saturation?

A
  • O2 bound to Hb/O2 capacity
  • measured using pulse oximeter/SpO2
  • arterial blood measured with blood gas analyser/ SaO2
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12
Q

What are some issues of pulse oximeters?

A
  • Measure amount of light absorbed by Hb
  • Darker skin
  • peripheral perfusion
  • restricted blood flow
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13
Q

What are the main points of the Oxygen dissociation curve?

A
  • Sigmoidal: PO2 can fall without much change in saturation
  • protection againt altitude + respiratory disease
  • P90 = 60mmHg/8kPa of PO2
  • P50 = 27mmHg/3.6kPa of PO2

P90/50 = % saturation of Hb

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14
Q

What is right shift in the oxygen dissociation curve?

CADET, face right

A
  • Bohr’s shift
  • high altitude, respiratory disease, anemia, exercise
  • Decreased affinity of Hb for O2
  • ↑CO2, ↑H+ (low pH), ↑2,3-DPG, ↑Temp

Right Releases

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15
Q

What is left-shift in the oxygen dissociation curve?

A
  • Fetal haemoglobin, Myoglobin
  • ↓CO2, ↓H+(high pH), ↓2,3-DPG, ↓Temp
  • Increased affinity of Hb for O2

in fetal, 2,3-DPG binds poorly to HbF

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16
Q

How does anemia affect Hb saturation and oxygen carrying capacity?

A
  • no effect on % Hb saturation
  • decreased O2 carrying capacity because of less Hb per 100ml blood
17
Q

How does carbon monoxide bind to Hb?

A
  • 240x more strongly than O2
  • carboxyhaemoglobin
  • shifts dissociation curve to the LEFT
  • leads to tissue hypoxia
  • odourless, colourless, tasteless so does not increase ventilation, person is not SOB
18
Q

What is cyanosis?

A
  • blue colouration of skin and mucous membranes; tongue, lips, nails, hands
19
Q

What is central cyanosis?

A
  • Due to arterial blood desaturation
  • arterial blood is 85% saturated

or when capillary blood is 70% saturated

20
Q

What is peripheral cyanosis?

A
  • Due to reduced tissue blood flow; vasoconstriction
  • Exposure to cold, Raynaud’s disease, vascular obstruction, reduced cardiac output
21
Q

How is CO2 carried in the blood?

A
  • Dissolved in plasma (5%)
  • Carbaminohaemoglobin/HbCO2 (3%)
  • Bicarbonate ions/HCO3- (92%)
22
Q

What is the arterial and venous CO2 blood content?

A
  • A = 48%
  • V = 52%
23
Q

How does CO2 become bicarbonate ions?

A
  • CO2 + H2O ⇌ H2CO3 ⇌ H+ HCO3-
  • first part catalysed by carbonic anhydrase
24
Q

What happens to H+ ions in the RBC?

A
  • Binds reversibly to Hb
  • buffer, limits shifts in pH
  • H+ + Hb ⇌ HbH+
25
Q

What is the chloride shift?

A
  • If HCO3- leaves RBC, inside of cell becomes too positive (H+ ions)
  • anion exchanger proteinBand 3
  • Cl- shifts into cell as HCO3- moves out
26
Q

What is reverse chloride shift?

A
  • occurs at lungs
  • O2 binds to Hb, so H+ released
  • HCO3- moves back into cell to be converted into CO2 and water
  • Cl- moves out
27
Q

What is the Haldane effect?

A
  • The deoxygenation of blood increases it’s ability to carry CO2
  • pH falls from 7.4 to 7.35 in venous blood
28
Q

How does the CO2 dissocation curve look like?

Haldane curve

A
  • LINEAR
  • transport of CO2 is dependent on O2 release
  • at PCO2 40mmHg, CO2 content is 48% (arterial)
  • at PCO2 46mmHg, CO2 content is 52% (venous)
29
Q

How does hypo and hyperventilation link with PaCO2?

A

Hyperventilation: PaCO2 < 40mmHg
- altitude, hysteria → respiratory alkalosis

Hypoventilation: PaCO2 > 40mmHg
- respiratory disease → respiratory acidosis

RESP (20 decks)

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