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Heart, Lungs and Blood > Gas exchange and gas transport > Flashcards

Gas exchange and gas transport Flashcards

1
Q

is oxygen very soluble in plasma

A

no

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2
Q

what is oxygen bound to in the blood

A

It is bound to haemoglobin (Hb) to form oxyhaemoglobin

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3
Q

when does the oxygen dissociation curve flatten

A

at higher levels of saturation

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4
Q

How does Hypoventilation/hyperventilation affect arterial O2 content

A

little change

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5
Q

what is P50

A

P50 is the partial pressure of oxygen at which 50% of Hb is saturated

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6
Q

what does the affinity of Hb for Oxygen depend on

A

pH, CO2 partial pressure and temp

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7
Q

what does an increase in the concentration of 2,3-DPG result in

A
  • a shift to the right
    • 2,3-DPG promotes hemoglobin transition from a high-oxygen-affinity state to a low-oxygen-affinity state
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8
Q

what happens if the the oxygen dissociation curve moves to the right

A

if the curve moves to the right means that the affinity is decreased so that there is a larger tendency to release oxygen rather than keep it to itself

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9
Q

what is the oxygen cascade

A

the oxygen cascade is the falling pressure of oxygen from air to mitochondria

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10
Q

what happens to air in upper conducting airways

A

it is humidified and does not participate on gas exchange

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11
Q

what does water vapour do to the ppO2

A

decreases

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12
Q

how does oxygen get transferred from the air to the mitochondria

A

From air → conducting airways → alveoli → interstitial space containing fluid → across the interstitium → red blood cell → bind to Hb → tissue fluid → across cell membrane → mitochondria

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13
Q

describe what happens to HB when oxygen binds to form oxyhaemoglobin

A

it is saturated

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14
Q

what is it called when deoxygenated Hb contains no o2

A

desaturated

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15
Q

what does oxygen delivery (DO2) depend on

A

Oxygen delivery (DO2) depends on cardiac output (CO) and arterial oxygen content (CaO2)

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16
Q

what is the calculation for oxygen delivery (DO2)

A
  • DO2 = CO x CaO2
  • CO = heart rate x stroke volume
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17
Q

what is the equation for oxygen consumption (VO2)

A
  • Oxygen consumption (VO2) = amount of O2 consumed/minute
    • VO2 max = CO x (CaO2 – CvO2)
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18
Q

what does the ratio of oxygen delivery and oxygen consumption in a healthy person

A

At rest in healthy person, DO2 > VO2

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19
Q

how is CO2 carried in the blood

A
  • 30% of CO2 carried as carbaminohaemoglobin
  • 10% of CO2 is carried dissolved in plasma
  • 60% of CO2 is transported as bicarbonate ions
    • CO2 + H2O ↔ H2CO3 ↔ H+ + HCO3 –
      Enzyme: carbonic anhydrase
20
Q

what are some characteristics of H+ in the blood

A
  • there is a high concentration of H+ in RBC
  • the membrane is impermeable to H+
21
Q

what is the Haldane effect

A
  • when Hb becomes deoxygenated in tissues it can take up more CO2
  • in alveoli, oxygenation of Hb results in the release of CO2
22
Q

what is respiratory acidosis

A

bicarbonate and deoxygenated Hb bind and release CO2 according to the pH

23
Q

what is the respiratory quotient

A

this is the ratio of CO2 production to O2 consumption

24
Q

what is PAO2, PACO2, PaO2

A
  • PAO2 = alveolar partial pressure of oxygen
  • PACO2 = alveolar partial pressure of carbon dioxide
  • PaO2 = arterial partial pressure of oxygen
25
Q

what is acinus

A

a unit of respiratory function distal to the terminal bronchioles comprising of the respiratory bronchioles, alveolar ducts and alveoli

26
Q

what is it called when many acinar are together

A

pulmonary lobule

27
Q

what are pulmonary lobules seperated by

A

septae

28
Q

what is the importance of structural interdependence in acinar

A

prevent collapse of an individual unit

29
Q

what does the number and size of alveoli depend on

A

No of alveoli depends on height of individual, size depends on volume of air in lungs

30
Q

what are alveoli lined by

A

thin layer of unciliated squamous epithelial cells

31
Q

where are type 1 pneumocytes

A

rest on the Basement Membrane and interface closely with capillary membrane = alveolar-capillary unit

32
Q

what is in the interstitial space

A

Interstitial space contains pulmonary capillaries, elastin and collagen fibres

33
Q

where are type 2 pneumocytes

A
  • found at the junction between alveoli and produce surfactant which reduced surface tension
34
Q

what are club cells/ bronchiolar exocrine cells

A

Club cells (Bronchiolar exocrine cells) in alveolar fluid produce glycosaminoglycans

35
Q

what is the insterstitium

A

The Interstitium is a microscopic space between the alveoli and the pulmonary capillary wall

36
Q

what are factors that affect diffusion

A
  • thickness of membrane
  • surface area of membrane
  • solubility of gas in the membrane
  • molecular weight of gas
37
Q

how can movement of O2 be estimated

A

The amount of CO transferred across/minute is estimated using a single-breath method-This is called TLCO/DLCO

38
Q

what is TLCO reduced by

A
  • TLCO will be reduced in conditions that affect:
    • The surface area available for gas exchange = emphysema
    • Thickening of the membrane = pulmonary fibrosis
39
Q

what is carboxyhaemoglobin (COHb)

A

is formed when Carbon Monoxide (CO) binds to Hb

40
Q

does haemoglobin have a higher affinity for O2 compared to CO

A

no

41
Q

what are the clinical symptoms for Co poisoning

A

headaches, N+ V, dizziness, lethargy; weakness, confusion, coma and death within hours

42
Q

what is methaemoglobin (MetHb)

A

Methaemoglobin (MetHb) arises when the Iron component in haemoglobin is oxidised so that it is in the ferric state (Fe3+)

43
Q

what is the binding like for MetHb

A

MetHb is unable to bind O2 and therefore cannot participate in O2 transport

44
Q

what are the causes of MetHb

A

Congenital/idiopathic methaemoglobinaemia
Infants become cyanosed
Acquired MetHB: post exposure to chemicals (anaesthetics, nitrobenzene, specific antibiotics )

45
Q

what is Congenital/idiopathic methaemoglobinaemia

A

this genetic defect leads to a deficiency of a certain enzyme, or protein. This protein is responsible for converting methemoglobin to hemoglobin

46
Q

what is cyanosis

A

happens when there’s not enough oxygen in your blood, or you have poor blood circulation

Heart, Lungs and Blood (51 decks)

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