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M103 T4 > M103 T4 L4 > Flashcards

M103 T4 L4 Flashcards

1
Q

How does pulse oximetry work?

A

put the finger probe on
light emitting diode and a receiver on the other side
the light goes through the finger and essentially detects the light with the receiver

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2
Q

What is PaO2 measured by?

A

an abg analyser

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3
Q

What might affect / nullify the results of pulse oximetry?

A

highly pigmented skin - lower reading than expected

nail varnish - completely nullifies the result

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4
Q

What is Type 1 respiratory failure usually caused by?

A

some kind of intrinsic lung disease affecting the airways or the vasculature

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5
Q

What is Type 2 respiratory failure usually caused by?

A

(brain) a reduction in ventilatory drive - this could be caused by an overdose of a sedative medication
(muscle) reduced neuromuscular power - some kind of myopathy
(receptors) resetting of chemoreceptors that drive ventilation

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6
Q

How is the base excess affected in metabolic alkalosis & acidosis?

A

increases in metabolic alkalosis

decreases in metabolic acidosis

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7
Q

What are the physiological causes of hypoxaemia?

A 
V/Q mismatch
Right-to-left shunt
Diffusion impairment
Hypoventilation
Low inspired pO2
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8
Q

equation for a-a gradient

A

PAO2 = PIO2 – (PaCO2/0.8)

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9
Q

What is the function of the a-a gradient?

A

indicates the integrity of the alveolocapillary membrane and the effectiveness of gas exchange
disease / pathology of the alveolocapillary unit widens the gradient

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10
Q

What is hypoxaemia where the a-a gradient widens caused by?

A

V/Q mismatch, diffusion limitation and shunt

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11
Q

What is the most common cause of hypoxaemia?

A

V/Q mismatch

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12
Q

How does V/Q change in different parts of the lungs?

A

V/Q ratio is higher at apex and low at the base

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13
Q

What is the name of the mechanism by which V/Q mismatches are compensated for? (HypPulVas)

A

hypoxic pulmonary vasoconstriction

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14
Q

What are symptoms of a high V/Q ratio?

A

when ventilation is in excess of perfusion

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15
Q

What compensation can occur for hypoxaemia?

A

a compensatory rise in total ventilation

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16
Q

How is hypoxaemia due to V/Q mismatch corrected?

A

supplemental oxygen

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17
Q

What are the common causative conditions of Hypoxaemia?

A

(ABCC.PH-ILD)

asthma
COPD
bronchiectasis
cystic fibrosis
ILD 
pulmonary hyptertension
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18
Q

What happens in a pulmonary shunt?

A

blood from the right side of the heart enters the left side of the heart without taking part in gas exchange
so it misses the pulmonary circulation
has a poor reaction to oxygen therapy

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19
Q

What are the signs of a pulmonary shunt?

A

A-a gradient is elevated
pCO2 is normal
Poor response to oxygen therapy

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20
Q

What are the common causes of a pulmonary shunt?

A

pneumonia
pulmonary oedema
acute respiratory distress syndrome
pulmonary arteriovenous malformations

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21
Q

What are the causes of diffusion limitation?

A

pulmonary fibrosis

hypoxaemia

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22
Q

Why is hypercapnea not usually associated with diffusion limitation?

A

CO2 is 20x more soluble than O2 and is less likely to be affected by diffusion limitation

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23
Q

What are the signs of diffusion limitation?

A

shows a good response to oxygen therapy
A-a gradient is elevated
PaCO2 is normal

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24
Q

What does the A-a gradient look like in hypoventilation?

A

Normal A-a gradient (low PAO2 then subsequent low PaO2)

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25
Q

How does hypoventilation react to oxygen therapy?

A

If hypoxaemia is present it is easily corrected by oxygen therapy
but hypoventilation and hypercapnoea can persist

26
Q

What are the causes of hypoventilation?

A

Impaired central respiratory drive (brain)
a disease of the spinal cord, NMJ or nerve (neural)
a myopathy in respiratory muscles (muscular)

27
Q

What are the signs of hypoventilation?

A

shows good response to oxygen therapy
A-a gradient is normal
PaCO2 is high

28
Q

What does the Beer-Lambert-Bougeur law state?

A

that the attenuation of light depends on the properties of the materials through which the light is travelling

29
Q

What causes the VQ mismatch in Type 1 respiratory failure?

A

the reduction in PaO2 but the lack of change in PaCO2

ventillation issue

30
Q

What causes underventilation in Type 1 respiratory failure?

A

the ics in PaCO2 and dcs in PaO2

31
Q

What physiological states are associated with Type 1 & 2 respiratory failure?

A

1 - hypoxia

2 - hypoxia with hypercapnia

32
Q

What group of patients usually experience hypercapnia?

A

people with COPD

makes it harder for them to breathe

33
Q

What is the normal pH of a litre of blood in terms of PaCO2?

A

PaCO2 of 40 mmHg

34
Q

What is the most common type of sleep apnoea?

A

obstructive sleep apnoea

35
Q

What is above normal for obstructive sleep apnoea?

A

5 or more obstructive apnoeas per hour

36
Q

What are statistical criteria features of hypopnea?

A

50% reduction in airflow
4% oxygen desaturation
and/or arousal from sleep

37
Q

What gases are delivered by a Venturi mask?

A

specific concentrations of oxygen by mixing oxygen with inhaled air

38
Q

What apparatus makes up a Venturi mask?

A

a face mask and reservoir bag device

39
Q

What mask delivers oxygen?

A

Hudson mask

uncontrolled and controlled mask

40
Q

What are the causes of a V/Q mismatch?

A

reduced ventillation

reduced perfusion

41
Q

What causes reduced ventilation (VQ mismatch)?

A

hypoventilation, low FiO2

42
Q

What causes reduced perfusion (VQ mismatch)?

A

diffusion impairment or pulmonary shunt (low perfusion)

43
Q

What does pulse oximetry measure?

A

oxygen saturation of Hb in the capillary beds

44
Q

What is SaO2 measured by?

A

abg analyser and a pulse oximeter

45
Q

What is the normal blood pH range?

A

7.35-7.45

46
Q

What three organs are involved in acid-base homeostasis?

A

lungs, kidneys and brain

47
Q

What structures are involved in acid-base homeostasis?

A

chemical buffers in blood
blood cells (erythrocytes)
the lungs, kidneys and brain

48
Q

Why isn’t the base excess widely used in metabolic acidosis and alkalosis?

A

its utility in interpreting blood gas results is controversial

49
Q

What could cause an impaired central drive, resulting in hypoventilation?

A

drug overdose, brainstem infarction, primary alveolar hypoventilation

50
Q

What could cause an impaired central respiratory drive, resulting in hypoventilation?

A

diseases of the spinal cord, NMJs or nerves

51
Q

What causes Myasthenia gravis?

A

antibodies destroying the communication between nerves and muscle

52
Q

How is the body affected in Myasthenia gravis?

A

weakness of the skeletal muscles

53
Q

How is Guillain-Barré syndrome pronounced?

A

geeyan baray

54
Q

What is an example of a spinal cord disease that could cause hypoventilation?

A

ALS

55
Q

What is an example of a nerve disease that could cause hypoventilation?

A

Guillian-Barre syndrome

56
Q

What is an example of an NMJ disease that could cause hypoventilation?

A

myasthenia gravis

57
Q

What are the first symptoms of Guillian-Barre syndrome?

A

weakness and tingling in extremities

58
Q

How does Guillian-Barre syndrome progress?

A

weakness and tingling in extremities quickly spread, eventually paralyzing the whole body

59
Q

What is the cause of Guillian-Barre syndrome?

A

unknown, but 2/3 of patients report symptoms of an infection in the six weeks before (respiratory, GI infections or zika virus)

60
Q

What is the effect of hypoventilation in healthy and unhealthy lungs?

A

healthy lungs - will not cause sufficient hypoxia

lung disease - will cause sufficient hypoxia

61
Q

What is hypoxaemia where the a-a gradient is normal caused by?

A

hypoxia and hypoventilation

M103 T4 (19 decks)

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