clinical blood gases Flashcards

1
Q

how is haemoglobin saturation measured

A

absorption spectrometry using a finger probe

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2
Q

what is most healthy peoples oxygen saturation

A

97%

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3
Q

2 different ways of measuring arterial blood gases (ABG)

A

single arterial puncture technique
in-dwelling arterial catheter or A-line

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4
Q

which artery is most commonly used for ABG measurement and which other 2 are used less often

A

radial artery
less commonly used:
femoral artery
brachial artery

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5
Q

what does a blood gas measure

A

PaO2
PaCO2
Hydrogen ion/pH
Bicarbonate
may also measure electrolytes and Hb

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6
Q

difference between PA and Pa

A

PA - partial pressure in alveolus
Pa - partial pressure in arterial circulation

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7
Q

normal blood gas values: H+

A

36-44nmol/l

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8
Q

normal blood gas values: PO2

A

12-15kPa

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9
Q

normal blood gas values: PCO2

A

4.4-6.1

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10
Q

normal blood gas values: HCO3 (bicarbonate)

A

21-27.5

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11
Q

what is BE

A

base excess (to do with metabolic blood gases)

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12
Q

normal blood gas values: BE

A

+2 to -2 mmol/l

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13
Q

difference between PAO2 and PaO2 values and why

A

PaO2: 12-15kPa
PAO2: 14-15kPa
oxygen dilution

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14
Q

what do carbon dioxide levels tell us about

A

ventilation

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15
Q

what happens to pCO2 and pO2 during hyperventilation

A

pO2 same, low pCO2

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16
Q

what happens to pCO2 and pO2 during hypoventilation

A

low pO2, high pCO2

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17
Q

what does increase of CO2 in blood lead to

A

acidosis

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18
Q

what is carbon monoxide (CO) produced from

A

incomplete combustion (mainly faulty gas boilers)

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19
Q

what does CO form when it binds to haemoglobin

A

carboxyhaemoglobin

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20
Q

how does CO damage the body

A

higher affinity to haemoglobin than oxygen so displaces it
also toxin to mitochondria

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21
Q

carbon monoxide treatment

A

high concentration oxygen - this displaces CO from haemoglobin

22
Q

what is respiratory failure

A

low oxygen level in the blood
PaO2<8kPa

23
Q

what is respiratory failure caused by

A

V/Q mismatch or hypoventilation

24
Q

what is the name for low oxygen levels in the blood

A

hypoxaemia

25
Q

type 1 respiratory failure blood gas levels

A

low PaO2
normal (or low) CO2

26
Q

what is type 1 respiratory failure caused by (mainly)

A

V/Q mismatch

27
Q

type 1 respiratory failure example

A

pneumonia

28
Q

what is V/Q mismatch

A

not enough oxygen or not enough blood being oxygenated

29
Q

what are other causes of type 1 respiratory failure

A

lung diseases affecting parenchyma
interstitial lung disease
bronchiectasis
obstructive airways disease (asthma, COPD - but can also cause type 2)
pulmonary embolism

30
Q

type 1 respiratory failure treatment

A

treat with oxygen while treating underlying cause

31
Q

type 2 respiratory failure blood gas levels

A

low PaO2
high PaCO2

32
Q

what is type 2 respiratory failure caused by

A

hypoventilation

33
Q

what is gas levels in type 2 respiratory failure due to and what can they lead to?

A

low O2 level due to hypoventilation
high CO2 due to increased levels in alveolar space and less removed from blood
acute rise in blood CO2 leads to respiratory acidosis

34
Q

other causes of type 2 respiratory failure

A

hypoventilation
opiate toxicity
neuromuscular disease
COPD
acute severe asthma

35
Q

asthma and respiratory failure - what suggests significant asthma attack

A

hypoxaemia

36
Q

COPD and respiratory failure - difference between type 1 and type 2

A

earlier stage - mucus and patches of emphysema, type 1
more severe - type 2
could be acute or chronic

37
Q

acidosis - equation

A

CO2 + H2O <-> H2CO3 <-> H+ + HCO3-

38
Q

what is H+ increased by

A

increase in pCO2 (respiratory acidosis)
increase in acid production or decrease in excretion (metabolic acidosis)

39
Q

acidosis - acute vs chronic type 2 respiratory failure

A

acute - yes
chronic - maybe not

40
Q

why does chronic type 2 respiratory failure often not have acidosis

A

low CO2 for so long that body compensates, raises bicarbonate levels to buffer this, therefore no acidosis

41
Q

acute type 2 respiratory failure - blood gas levels

A

low oxygen
high carbon dioxide
high H+
normal bicarbonate

42
Q

chronic type 2 respiratory failure - blood gas levels

A

low oxygen
high carbon dioxide
normal H+
high bicarbonate

43
Q

problem with chronically high CO2 levels?

A

high CO2 levels normally stimulates breathing, if it is chronic it is compensated for so will no longer to this therefore become dependant on hypoxia to stimulate breathing

44
Q

why could oxygen therapy for patients with chronic type 2 respiratory failure be bad? how should they be treated?

A

because CO2 levels will rapidly rise higher making them more hypoxemic because of the effects of CO2 narcosis. treated with controlled oxygen, monitor response.

45
Q

which type of respiratory failure could oxygen therapy be bad for?

A

chronic type 2 respiratory failure

46
Q

what is respiratory alkalosis caused by

A

hyperventilation

47
Q

respiratory alkalosis blood gas levels

A

low PCO2 and low H+

48
Q

conditions causing excess production of acid

A

lactic acidosis
diabetic ketoacidosis

49
Q

what is a classic sign of acidosis

A

kussmal breathing - breathing more quickly and deeply to try get rid of acid

50
Q

what blood gas level is a sign of metabolic acidosis

A

high acid, LOW bicarbonate

51
Q

what does standard bicarbonate mean?

A

no metabolic component to illness