13 Hypoxia and Respiratory Failure Flashcards

1
Q

Differentiate between hypoxia and hypoxaemia

A
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2
Q

Give examples of when a patient might be hypoxic but not hypoxaemic

A
  • Severe anaemia
  • Poor perfusion
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3
Q

What is respiratory failure? Differentiate between Type 1 an Type 2 respiratory failure.

A

Respiratory failure= pO2< 8kPa when breathing air at sea level

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4
Q

What systemic effects does hypoxia have?

A
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5
Q

What systemic effects does hypercapnia have?

A
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6
Q

What are the causes of hypoxaemia? (5)

A
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7
Q

What effects does chronic hypoxaemia have?

A
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8
Q

Explain why someone who is acutely exposed to high altitudes (atmospheric pressue <101kPa) will have a low pO2 and low pCO2.

A

Low inspired pO2 level

Peripheral chemoreceptors stimulated

–> Hyperventilation– causes low pCO2

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9
Q

What adaptations does someone who lives at high altitudes have?

A
  • Polycythaemia
  • Increased 2-3 DPG
  • Increased capillary density
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10
Q

Is hypoventilation a type 1 or type 2 respiratory failure? Why?

A

Type 2

Elevated pCO2

(Artificial ventilation required)

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11
Q

Give some causes of hypoventilation.

A
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12
Q

Explain why a patient with with COPD will not require ventilatory support until the later stages of the condition.

A

Time allowed for some compensatory mechanisms to develop

(May need ventilation during acute complications eg lung infection)

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13
Q

Outline how the body responds to chronic hypercapnia. (Kidney and Central chemoreceptors)

A

Kidney: renal compensation of respiratory acidosis

Central chemoreceptors: Choroid complex imports HCO3- into CSF. Restores CSF pH to normal. Central chemoreceptors ‘reset’

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14
Q

How would you treat hypoxia in a patient with chronic type 2 respiratory failure?

Check bicarb- may be only sign of CO2 retention

A

Controlled oxygen therapy- avoid risk of worsening hypercapnia

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15
Q

Explain how a V/Q mismatch (due to poor ventilation of alveoli/pulmonary embolism) leads to Type 1 respiratory failure.

(eg COPD-early stages, asthma, RDS, pneumonia, pulmonary embolism)

A
  • Drop in pO2
  • Hyperventiation stimulated- increased CO2 removal
  • Hyperventilation insufficient to correct fall in pO2
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16
Q

Explain why a diffusion impairment within the alveoli causes type 1 respiratory failure and not type 2.

A

O2 diffuses less readily than CO2 - always affected more by any change in diffusion barrier

17
Q

Give an example of a condition which can initally cause Type 1 respiratory failure that can progress to Type 2 respiratory failure and explain how this happens

A

Asthma

More and more airways- narrowed, exhaustion sets in

Ventilatory support required

18
Q

Explain why treating a hypoxic patient with uncontrolled oxygen can only worsen hypercapnia. (2 mechanisms)

How should it be controlled instead?

A

Controlled oxygen therapy- continuously monitor oxygen and CO2 levels

19
Q

What is a patient going to require if controlled oxygen therapy still causes hypercapnia?

A

Assisted ventilation