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Respiratory System > Hypoxia And Respiratory Failure > Flashcards

Hypoxia And Respiratory Failure Flashcards

1
Q

What is hypoxia?

A

Oxygen deficiency at tissue level

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2
Q

Name the different types of hypoxia

A

Hypoxaemic
Anaemic
Stagnant/circulatory
Cytotoxic

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3
Q

Describe hypoxaemic hypoxia

A

Caused by respiratory failure

Poor oxygenation in the lungs

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4
Q

Describe anaemic hypoxia

A

Insufficient oxygen bound to Hb

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5
Q

Describe stagnant/circulatory hypoxia

A

Poor perfusion to regional arteries
Reduced oxygen delivery
Can be global or local

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6
Q

Describe cytotoxic hypoxia

A

Problem getting oxygen into tissues and using it in these cells
Eg. Cyanide poisoning

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7
Q

Define anaemia

A

Normal partial pressure of oxygen but insufficient haemoglobin

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8
Q

What is the normal range for oxygen saturation?

A

94 - 98%

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9
Q

What is the normal range for partial pressure of oxygen?

A

11.1 - 14.4 kPa

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10
Q

Tissue damage is most likely to occur when oxygen sats or partial pressure oxygen falls below …

A

Oxygen sats < 90%

Partial pressure O2 < 8kPa

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11
Q

Describe a type 1 respiratory failure

A

Partial pressure of oxygen arterial blood low (<8)
Oxygen sats <90%
But carbon dioxide levels are normal or low
(Type 1 affects 1 - oxygen)

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12
Q

Describe a type 2 respiratory failure

A

Partial pressure of oxygen in arterial blood <8
Oxygen sats <90%
And partial pressure of CO2 is high

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13
Q

What is the normal partial pressure range for CO2 in plasma?

A

4.3 - 6.4 kPa

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14
Q

What are the 3 general mechanisms of respiratory failure?

A

Ventilatory failure - unable to move sufficient air in and out
Poor diffusion across alveoli
V/Q mismatch
(More than one mechanism may be operating in a given disease)

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15
Q

Give examples of things that cause hypoventilation

A 
Opiates
Brain injury 
Myasthenia gravis/Guillain-Barre
Myopathy/MND
Obesity 
Kyphoscoliosis 
Pneumothorax 
Large effusions
Lung fibrosis 
RDS
Foreign body 
Severe asthma 
COPD (late)
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16
Q

Give some causes of chronic type 2 respiratory failure

A 
Myopathy 
MND
Obesity 
Kyphoscoliosis 
Lung fibrosis 
Late stages COPD
17
Q

What is a flail segment?

A

Segment of the chest wall where multiple ribs are fractured in 2 places
During inspiration the segment gets sucked inwards
Preventing adequate lung expansion

18
Q

What are the acute effects of type 2 respiratory failure?

A

Partial pressure CO2 rises, oxygen falls
Central chemoreceptors stimulated - increase in ventilation
Unable to completely correct due to disease causing
Respiratory acidosis
Assisted ventilation needed

19
Q

What is the commonest cause of Type 2 resp failure?

A

Acute exacerbation of COPD

20
Q

Give some examples of how diffusion is compromised in certain resp diseases

A

Lung fibrosis - increased thickness of membrane

Emphysema - surface area decreased

21
Q

How do we work out AVR?

A

(Tidal volume - dead space) x resp rate

22
Q

What happens to resp system in a PE?

A

Reduced blood flow to an area (V/Q > 1)
Blood diverted to other parts of the lungs
More blood available than can be used (V/Q <1)
Hypoxia

23
Q

Other than respiratory failure, name some consequence of a massive PE

A

Acute right heart failure (increased resistance in pulmonary circulation)
Reduce cardiac output - circulatory collapse

24
Q

How do we manage respiratory failure?

A

Treat cause of the failure
Oxygen therapy - improve hypoxia
In type 2, problem of hypercapnia often requires assisted ventilation

25
Q

Give some clinical features of hypoxia

A

Exercise intolerance
Confusion
Tachypnoea
Central cyanosis

26
Q

What is cyanosis?

A

Bluish discolouration of skin and mucous membranes due to the colour of desaturated Hb
Present if >50gm/L desaturated Hb in blood

27
Q

What are the effects of chronic hypoxia?

A

Increased EPO causing elevated Hb levels
Increased 2,3 - BPG in RBCs
Hypoxia vasoconstriction of pulmonary arterioles
(Pulmonary hypertension, RH failure, cor pulmonale)

28
Q

Give 2 clinical signs of chronic hypercapnia

A

Warm hands

Flapping tremor

29
Q

What happens to the chemoreceptors in chronic hypercapnia?

A

CSF acidity corrected by addition of bicarbonate by the choroid plexus cells
Now reset to a higher partial pressure of CO2
Peripheral chemoreceptors remain sensitive to hypoxia
Respiration is now driven by hypoxia

30
Q

Why do we need to be careful when treating someone with chronic hypercapnia?

A

Giving them oxygen therapy
Correction of hypoxia may reduce their ventilation because their hypoxia is driving their breathing
This may worsen the hypercapnia
Must use titrated oxygen therapy

Respiratory System (13 decks)

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