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Year 1 HLB Respiratory > Respiratory Gas Exchange and Transport > Flashcards

Respiratory Gas Exchange and Transport Flashcards

1
Q

Once O2 enters the lungs how does it get to the tissues?

A
  • O2 diffuses across alveoli membrane - enters pulmonary capillaries - returns to heart via pulmonary vein - distributed around the body
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2
Q

How is CO2 removed from pulmonary capillaries?

A
  • diffuses across capillary membrane and into lungs - down concentration gradient - expired out of lungs
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3
Q

What is the interstitium?

A
  • small space between alveolar and capillaries
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4
Q

What are the cells of the capillaries and alveolar?

A
  • capillaries = simple squamous epithelial cells - alveoli = squamous (type 1) and cuboidal (type 2) epithelial cells
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5
Q

Roughly how big is normal interstitium space?

A
  • aprox 0.5um
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6
Q

What are the 2 types of cells in the alveolar?

A
  • type 1 cells = squamous - type 2 cells = cuboidal
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7
Q

What is partial pressure?

A
  • in a mixture of gases - individual gases exert a pressure - this is called partial pressure
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8
Q

What is the total pressure in relation to partial pressures?

A
  • the sum of all the partial pressures added together
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9
Q

Instead of referring to concentration gradients, what should we refer to when talking about gas exchange?

A
  • partial pressure = concentrations
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10
Q

Instead of referring to high and low concentration gradients gradients, what should we refer to when talking about gas exchange?

A
  • high and low diffusion gradients
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11
Q

Does gas move up of down diffusion gradients?

A
  • partial pressures always move down pressure gradients
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12
Q

What does O2 saturation, also referred to as SATs mean?

A
  • level of O2 bound to haemoglobin in red blood cells - measured as SaO2 % (% of O2 bound to haemoglobin)
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13
Q

What is the normal range for haemoglobin in the body for males and females?

A
  • male = 13.8 - 17.2 g/dL - female = 12.1 - 15.1 g/dL
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14
Q

What are a few things that can affect the amount of haemoglobin in the body?

A
  • age - gender - ethnicity
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15
Q

What are normal O2 saturation levels?

A
  • 94-99%
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16
Q

What are normal O2 saturation levels in COPD patients?

A
  • 88-92%
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17
Q

What O2 saturation level would be classified as hypoxic?

A
  • <88%
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18
Q

What does SpO2 mean?

A
  • amount of O2 bound to haemoglobin - relative to the haemoglobin not carrying oxygen - measured by blood gas analysis
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19
Q

What does SaO2 mean?

A
  • amount of O2 bound to haemoglobin - relative to the haemoglobin not carrying oxygen - measured by pulse oximetry
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20
Q

What does the Oxygen Dissociation curve SpO2 tell us?

A
  • shows tight relationship between O2 partial pressure and O2 saturation of haemoglobin
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21
Q

What shape is the curve in the Oxygen Dissociation curve SpO2?

A
  • sigmoid shape
  • like and S curve
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22
Q

Where the Oxygen Dissociation curve plateaus, would an increase in O2 partial pressure (PaO2) change oxyhemoglobin saturation?

A
  • no
  • already around 98% so no real change
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23
Q

At 50% partial pressure on the Oxygen Dissociation curve, would a change in O2 partial pressure (PaO2) change oxyhemoglobin saturation?

A
  • yes
  • small changes in PaO2 have a large effect on oxyhemoglobin saturation
24
Q

Would PaO2 (O2 partial pressure) be highest in the arterial or venous blood flow?

A
  • arterial
  • delivering O2 to tissues
  • venous is left over or reserve
25
Q

When might we expect to see the Oxygen Dissociation curve shift to the left?

A
  • at the lungs
  • at lower PaO2 would still ⬆️ oxyhemoglobin saturation
  • O2 affinity for haemoglobin is highest at the lungs
26
Q

When might we expect to see the Oxygen Dissociation curve shift to the right?

A
  • at the tissues during exercise
  • O2 affinity is low to increase diffusion into tissues
27
Q

What would a shift in Oxygen Dissociation curve shift to the right do to pH, temperature, CO2 levels and O2 affinity?

A
  • temperature = ⬆️
  • CO2 = ⬆️
  • pH = ⬆️
  • O2 affinity = ⬇️
28
Q

What would a shift in Oxygen Dissociation curve shift to the right do to pH, temperature, CO2 levels and O2 affinity?

A
  • temperature = ⬆️
  • CO2 = ⬆️
  • pH = ⬇️
  • O2 affinity = ⬇️
29
Q

What are the 4 main things that can affect the Oxygen Dissociation curve?

A
  • pH
  • temperature
  • 2,3 BPG (reduces O2 affinity) (also known as DPG)
  • PCO2
30
Q

What does oxyhemoglobin mean?

A
  • O2 bound to haemoglobin
31
Q

What is the diffusing capacity for carbon monoxide (DLCO) test used for?

A
  • assess lung function - specifically ability how much air gets to erythrocytes - overall function of capillary membrane
32
Q

Does carbon monoxide or O2 have a higher affinity for haemoglobin?

A
  • carbon monoxide - aprox 213 times more affinity and soluble in blood
33
Q

What is the normal process for DLCO?

A

1 - inhale gas including O2, helium and 0.3% CO 2 - breath hold for up to 10 seconds 3 - breathe out and discard first 1 litre 4 measure air after 1st litre

34
Q

What is the measurement of the DLCO?

A
  • CO able to diffuse per minute
35
Q

What is a severe impairment in lung function measured by DLCO?

A
  • <40%
36
Q

Patients with emphysema are likely to have an impaired DLCO, why?

A
  • alveolar are damaged
  • ⬇️ alveolar membrane surface
  • ⬇️ area for diffusion
37
Q

Patients with pulmonary fibrosis are likely to have an impaired DLCO, why?

A
  • interstitium becomes scarred, causing thickening
  • ⬆️ interstitium thickness causes ⬇️ diffusion
38
Q

Patients with pulmonary hypertension are likely to have an impaired DLCO, why?

A
  • blood vessels to alveoli are compressed reducing blood flow
  • ⬇️ blood flow means ⬇️ diffusion
39
Q

Patients with anaemia are likely to have an impaired DLCO, why?

A
  • less haemoglobin bound to blood - ⬇️ haemoglobin to bind with blood - ⬇️ diffusion
40
Q

What is the respirator quotient (RQ)?

A
  • ratio between CO2 and O2 absorbed
41
Q

What can the respirator quotient (RQ) tell us about fuel source?

A
  • RQ number indicates main substrate for energy - 1 = carbohydrates - 0.7 = fats - 0.8 = proteins
42
Q

What is the main role of CO2 in the blood?

A
  • maintain pH
43
Q

What is the formula for converting CO2 in H+ through carbonic anhydrase?

A
  • CO2 + H2O = carbonic acid = HCO3- + H+ - all facilitated by carbonic anhydrase
44
Q

What does CO2 and H+ do to blood pH?

A
  • reduces blood pH
45
Q

What is a common cause of alkalosis?

A
  • hyperventilation
  • increased CO2 removed from body
  • imbalance between HCO3- and CO2
46
Q

What is a common cause of acidosis?

A
  • obesity or asthma
47
Q

What is carboxyhemoglobin?

A
  • when carbon monoxide (CO) is bound to haemoglobin - COHb - able to bind with iron on haemoglobin
48
Q

What can concentrations of carbon monoxide as low as 0.1% do to SaO2 in the blood?

A
  • ⬇️ SaO2 - ⬇️ oxyhemoglobin - 50% of haemoglobin convert to carboxyhemoglobin
49
Q

Inhaling concentrations of carbon monoxide as low as 0.1% can cause symptoms, how quickly can this happen??

A
  • <1 hour
50
Q

Inhaling concentrations of carbon monoxide as high as 0.2% can cause death, how quickly can this happen??

A
  • <2 hours
51
Q

What is methaemoglobin?

A
  • when iron on haemoglobin becomes oxidised
  • becomes Fe3+ instead of Fe2 (this normally happens whjen O2 binds
  • Fe3+ called ferric state
  • O2 unable to bind to heme
52
Q

What can high levels of methaemoglobin cause?

A
  • ⬇️ O2 binding to haemoglobin - ⬇️ SaO2 - ⬇️ in respiratory function
53
Q

In patient with methaemoglobin, what colour is their skin and blood?

A
  • brown blood - blue skin due to lack of O2
54
Q

What is the main cause of methaemoglobin from birth?

A
  • congenital birth defects - causes deficiency in coenzyme factor 1
55
Q

What is the main cause of methaemoglobin from inheritance?

A
  • autosomal recessive congenital - 2 forms of defective gene
56
Q

Can methaemoglobin be acquired?

A
  • yes - due to chemical exposure, antibiotics, dapsones, chloroquine or nitrates
57
Q

How is Diffusing Capacity for Carbon Monoxide (DLCO) calculated?

A
  • measured in ml/min/mmHg
  • measured as a % of normal age matched ml/min/mmHg

Year 1 HLB Respiratory (25 decks)

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