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RCV 1 - physio > gas transport, control of ventilation & ABGS > Flashcards

gas transport, control of ventilation & ABGS Flashcards

1
Q

how is oxygen transported in the blood?

A

-bound to haemoglobin - 98%
-dissolved in plasma 2%

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2
Q

how is CO2 transported in the blood?

A

-bicarbonate -92%
-bound to Hb -3%
-dissolved in plasma 5%

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3
Q

what are the 3 different receptors that control ventilation in the lungs?

A

-mechanoreceptors
-irritant receptors
-chemoreceptors

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4
Q

how do mechanoreceptors control ventilation?

A

-respond to stretch during inflation
-a very large inflation can lead to critical stretch of the lung parenchyma (alveoli) causing the herni bruer reflex

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5
Q

where are the mechanoreceptors found in the resp system?

A

-bronchial smooth muscle, trachea and visceral pleura

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6
Q

how do irritant receptors work on controlling ventilation?

A

-respond to irritants such as cigarette smoke, dust allergens or secretions
-they cause a change in respiratory depth or frequency and induce a cough, sneeze or bronchospasm

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7
Q

why are chemoreceptors important in controlling ventilation?

A

-they constantly sample arterial blood to maintain resp gases and PH within normal range

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8
Q

what is the function of the central chemoreceptors (in the brainstem)?

A

-their function is to sense increased H+ concentration in the CSF

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9
Q

what are the peripheral chemoreceptors most sensitive to?

A

low pO2 in the arterial blood

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10
Q

describe the normal cycle of control of ventilation in a patient with a slight increased pCO2 level in blood and CSF?

A

-increased pco2 will stimulate the central chemoreceptors In medulla
-this stimulates the inspiratory muscles
-increases the respiratory rate
-removes more co2 from the body
-decreases PCO2
-decreases chemoreceptor stimulation

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11
Q

what is respiratory failure?

A

a clinical condition that happens when the resp system fails to maintain its main function, which is gas exchange
-ie Pa02 is reduced (lower than 60mmHg) and or paCO2 is raised (ie above 50mmHg)
-classified into type 1 or type 2

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12
Q

what is type 1 resp failure?

A

-hypoxemia
- low levels of oxygen (below 60mmHg) with normal or subnormal paCO2
-gas exchange is impaired at the level of he alveolo-capillary

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13
Q

what are examples of type 1 resp failure?

A

-covid 19
-severe pneumonia
the lungs can still excrete CO2 / ie get rid of it

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14
Q

what is type 2 respiratory failure?

A

-hypoxemia (pa02 is less than 60mmHg)
-hypercapnia - raised PaC02 levels (higher than 50mmHg)
-common in COPD patients

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15
Q

describe the hypoxic drive theory

A
  • in normal healthy people, elevated CO2 will drive respiration
    -but in COPD pts, they will have chronically high CO2 levels
    -in some pts, their chemoreceptors have become desensitised to the elevated CO2
    -therefore, in these patients it is the decreased O2 (hypoxia) that drives respiration
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16
Q

what is a risk if you give a COPD patient too much oxygen therapy?

A

-it can blunt their hypoxic drive
-therefore, there respiration will begin to slow causing further rise in CO2 levels and potential loss of consciousness

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17
Q

what SP02 levels are acceptable for people with COPD?

A

between 88-92%

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18
Q

describe v/q mismatching w/ the administration of oxygen therapy

A

-poorly ventilated alveoli cause the body to redistribute blood flow - alveolar vasoconstriction
-administering O2 will cause vasodilation
-alveoli are still poorly ventilated but are now better perfused - causing a V/Q mismatch

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19
Q

describe the haldane effect

A

-describes how the binding of oxygen to haemoglobin affects the binding and release of carbon dioxide (CO₂) in the blood.
- how the deoxygenation of blood increases its ability to carry CO2

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20
Q

what is hypoxia?

A

reduced level of tissue oxygenation

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21
Q

what is hypoxemia?

A

it is defined as a decrease in the partial pressure of oxygen in the blood

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22
Q

give an example of when a patiet can develop hyoxemia without hypoxia?

A

if there is a compensatory increase in Hb level and cardiac output - therefore more O2 can get to the tissues

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23
Q

what can cause hypoxaemia (low levels of o2 in blood)?

A

-respiratory depression
-resp muscle weakness
-obstructive airway diseases
-pulmonary oedema
-acute resp distress syndrome
alveolar collapse
-pneumothroax

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24
Q

what are examples of treatment hypoxemia?

A

-supplemental oxygen
-physio - positioning, clearance of secretions
-non invasive ventilation etc
-mechanical ventilation - sedated - eliminates the metabolic cost of breathing

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25
Q

how is hypoxemia classified?

A

-mild - 90-94%
-moderate -75-89%
-severe-75%

26
Q

what are examples of clinical features of hypoxia?

A

-SOB
-cyanosis (blue or purple discolouration)
-arrhythmias
-peripheral vasodilation
-systemic hypotension
-hypoventilation

27
Q

where is a blood sample taken for ABGs?

A

taken from the radial artery located in the wrist

28
Q

what 2 sets of information can be obtained from ABGs?

A

-blood oxygenation
-blood acid-base balance

29
Q

what is the purpose of ABG’s?

A

-evaluate acid-base status
-evaluate oxygenation status
-evaluate adequacy of ventilation
-to monitor pt
-to evaluate treatment

30
Q

what are the 5 components of ABG’s?

A

-PH
-PaCO2
-PaO2
-HCO3
-SaO2

31
Q

what is the normal PH of blood?

A

7.35-7.45

32
Q

what are the normal levels of CO2 in arterial blood? In kPa ?

A

-4.6-6kPa

33
Q

what are the normal levels of oxygen in the blood in kPa?

A

-10.6-13.3kPa

34
Q

what are normal levels of HCO3 in arterial blood in mmol/L?

A

22-26mmol/L

35
Q

what are normal SaO2 levels?

A

95-100

36
Q

define PH

A

the measure of H+ ions in the blood

37
Q

what is a blood PH below 7.35 termed?

A

acidotic

38
Q

what is a blood PH above 7.45 termed?

A

alkalotic

39
Q

what does BE stand for?

A

base excess

40
Q

what are the 2 buffering systems in the body to keep the blood PH as close to 7.4 as possible?

A

-the resp system and dissolved CO2
-the renal system - dissolved bicarbonate (HCO3) produced by the kidneys

41
Q

what its an very important chemical equation in terms of HCO3-, H+, CO2 and H20?

A

CO2+ H20== H2CO3= HCO3- + H+

42
Q

what impact does the resp system have on the important chemical equation?

A
  • it manipulates the CO2 levels
    -increasing or decreasing the RR does this
43
Q

how does the renal system impact the chemical equation?

A

it produces or retains HCO3- by eliminating hydrogen ions

44
Q

what are the 4 possibilities outside the normal range for ABG results?

A

-respiratory acidosis
-respiratory alkalosis
-metabolic acidosis
-metabolic alkalosis

45
Q

describe respiratory acidosis

A
  • clinical disturbance due to alveolar hypoventilation
    -production of CO2 occurs rapidly, and failure of ventilation promptly increases the partial pressure
46
Q

why can resp acidosis happen?

A

-airway obstruction eg COPD, asthma
-depression of resp centre - eg sedatives etc
-pulmonary disorders eg fibrosis, ARDs
-neuromuscular disorders eg MND

47
Q

what are examples of symptoms of resp acidosis?

A

-rapid, shallow respirations
-decrease in BP
-headache
-increase HR or CO
-muscle weakness

48
Q

what would respiratory acidosis look like on ABG results?

A

-PH would be lower than 7.35
-PaCO2 would be increased
-HCO3 would be normal (no metabolic compensation)

49
Q

describe respiratory alkalosis

A

-a clinical disturbance due to alveolar hyperventilation
-leads to decreased partial pressure of CO2

50
Q

what can cause resp alkalosis?

A

-pain
-anxiety
-PE
-aspiration
-pneumonia
-hyperthyroidism

51
Q

what are examples of symptoms of resp alkalosis?

A

-seizures
-deep rapid breathing
-hyperventilation
-tachycardia
-normal or low BP
-lethargy and confusion
-nausea and vomiting

52
Q

how would resp alkalosis look like on a ABG?

A

-PH is high or above 7.45
-paCO2 is decreased !!

53
Q

what is metabolic acidosis?

A
  • a process where blood PH is low due to increased production of H+ by the body without enough HCO3- to neutralise it
54
Q

why can metabolic acidosis occur?

A
  • can occur due to gain of acid or loss of base
    GAIN OF ACID
    -increased H+ formation eg lactic acidosis
    -decreased H+ exception eg renal failure
    -ingestion of acid eg poisoning
    LOSS OF BASE
    -loss of bicarbonate
    -eg dehydration ,and diarrhoea
55
Q

what are examples of symptoms of a pt with metabolic acidosis?

A

-headache
-low BP
-muscle twitching
-warm or flushed skin
-decrease muscle tone
-hyperventilation

56
Q

what does metabolic acidosis look like on an ABG?

A

-PH is decreased
-HCO3- decreased

57
Q

what is metabolic alkalosis?

A

results from hydrogen ion loss or excessive intake of alkaline substances

58
Q

how can metabolic alkalosis occur?

A

-GAIN OF BASE
- alkali administration eg sodium bicarbonate
LOSS OF ACID
-loss of H+ ions eg vomiting, NG suctioning
-shift of H+ ions into intracellular space eg hypokalemia

59
Q

what are examples of symptoms associated with metabolic alkalosis?

A

-restlessness
-compensatory hypoventilation
-tachycardia
-confused
-loss of consciousness
-muscle cramps

60
Q

what does metabolic alkalosis look like on an ABG?

A

-PH is high
-HCO3 is increased

RCV 1 - physio (16 decks)

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