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Respiratory system > Respiratory failure > Flashcards

Respiratory failure Flashcards

1
Q

What is respiratory failure?

A

Impaired gas exchange

caused hypoxaemia and hypoxia

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2
Q

What is pO2 with respiratory failure?

A

Less than 8kPa

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3
Q

What is meant by O2 saturation?

A

% saturation of haemaglobin

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4
Q

What is O2 saturation with respiratory failure?

A

Less than 90%

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5
Q

What are the types of respiratory failure?

A

Type 1

Type 2

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6
Q

What is the difference between type 1 and type 2 respiratory failure?

A

Type 1 respiratory failure has normal or low pCO2

Type 2 respiratory failure has high pCO2, hypercapnia

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7
Q

What are the causes of type 1 respiratory failure?

A

Low inspired pO2

V/Q mismatch

Diffusion problem

Right to left shunt

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8
Q

What is V/Q mismatch?

A

V/Q ratio of less than 1

or more than 1

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9
Q

How does reduced ventilation of an alveolus affect its V/Q ratio?

A

V/Q ratio is less than 1

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10
Q

What is an alveolus’ pO2 and pCO2 with reduced ventilation?

A

Low pO2
because is inspiring less oxygen

High pCO2
because is expiring less carbon dioxide

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11
Q

What is the physiological response to an alveolus with low pO2? Why?

A

Pulmonary hypoxic vasoconstriction

to redirect blood to better ventilated alveoli

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12
Q

What is plasma pO2 and pCO2 of blood from an alveolus with reduced ventilation?

A

Low pO2
because less oxygen is diffusing from alveolus into pulmonary capillaries

High pCO2
because less carbon dioxide is diffusing from pulmonary capillaries into alveolus

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13
Q

What is the physiological response to low plasma pO2?

A

Stimulates peripheral chemoreceptors

stimulates increased alveolar ventilation

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14
Q

How does increased alveolar ventilation affect the low alveolar pO2 and high alveolar pCO2?

A

Affected alveolus still has low pO2 and high pCO2

Normal alveoli have high pO2 and low pCO2

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15
Q

How does increased alveolar ventilation affect the low plasma pO2 and high plasma pCO2?

A

Blood from affected alveolus still has low pO2 and high pCO2

Blood from normal alveoli have small increase in plasma pO2, also Hb is fully saturated so no increase in bound O2, overall small increase in total content of O2
decrease in pCO2 because expiring more carbon dioxide

Overall, plasma pO2 still low
plasma pCO2 decreased to normal

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16
Q

What are some of the causes of alveolar V/Q mismatch?

A

Asthma

Pulmonary edema

Pulmonary embolism

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17
Q

What conditions affect the respiratory membrane?

A

Fibrosis

Pulmonary oedema

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18
Q

How does fibrosis affect the respiratory membrane?

A

Fibrous tissue in respiratory membrane

increases thickness of respiratory membrane

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19
Q

How does pulmonary oedema affect the respiratory membrane?

A

Increased tissue fluid in respiratory membrane

increases thickness of respiratory membrane

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20
Q

How does an increased thickness of the respiratory membrane affect plasma pO2 and pCO2?

A

Low plasma pO2
reduced diffusion rate of oxygen across respiratory membrane

Normal plasma pCO2
carbon dioxide has a higher diffusion coefficient
less affected diffusion rate across respiratory membrane

21
Q

What is the cause of type 2 respiratory failure?

A

Hypoventilation

22
Q

How does hypoventilation affect alveolar pO2 and pCO2?

A

Low alveolar pO2, because less inspired oxygen

High alveolar pCO2, because less carbon dioxide expired

23
Q

How does hypoventilation affect plasma pO2 and pCO2?

A

Low plasma pO2, because less oxygen diffuses from alveoli into pulmonary capillaries, hypoxia

High plasma pCO2, because less carbon dioxide diffuses from pulmonary capillaries into alveoli, hypercapnia

24
Q

How does hypoventilation affect plasma pH?

A

Higher concentration of carbon dioxide dissolved in plasma
favours forwards bicarbonate buffer reaction
increases concentration of hydrogen ions
decreases plasma pH

25
Q

What is the name of the condition of decrease in plasma pH due to hypoventilation?

A

Respiratory acidosis

26
Q

What are the causes of acute hypoventilation?

A

Head injury, spinal cord injury

Opiate overdose

Myasthenia gravis

Acute asthma exacerbation

Pneumothorax

Pleural effusion

Respiratory distress of the newborn

27
Q

What are the signs and symptoms of acute hypoxaemia?

A

Confusion, reduced consciousness

Cyanosis - central and peripheral

Cardiac arrythmias

Pulmonary hypoxic vasoconstriction

28
Q

What is cyanosis?

A

Blue-ish discolouration of skin and mucous membranes

29
Q

What causes cyanosis?

A

High levels of deoxygenated haemaglobin

30
Q

What are the types of cyanosis?

A

Peripheral

Central

31
Q

What is peripheral cyanosis?

A

Blue-ish discolouration seen in fingers, toes

32
Q

What causes peripheral cyanosis?

A

Poor local circulation

33
Q

What is central cyanosis?

A

Blue-ish discolouration of oral mucosa, tongue, lips

34
Q

What causes central cyanosis?

A

Hypoxaemia

35
Q

What are the causes of chronic hypoventilation?

A

Motor neurone disease

Myopathy

Obesity

Kyphoscoliosis

Fibrosis

Severe COPD

36
Q

What are the signs and symptoms of chronic hypoxaemia?

A

Increased EPO, polycythaemia

Increased 2,3-BPG

Pulmonary hypertension, right-sided heart failure = cor pulmonale

37
Q

Why is there increased EPO and polycythaemia wih chronic hypoxaemia?

A

Chronic hypoxaemia stimulates kidneys to produce more EPO

EPO stimulates bone marrow to produce more red blood cells

38
Q

Why is there increased 2,3-BPG with chronic hypoxaemia?

A

So haemaglobin has a lower affinity for oxygen

released more oxygen to tissues

39
Q

What are the signs and symptoms of acute hypercapnia?

A

Headache, confusion

Muscle twitches

Flushed skin

Bounding pulse

40
Q

What causes a headache with acute hypercapnia?

A

Cerebral arteries vasodilation

41
Q

What causes flushed skin and a bounding pulse with hypercapnia?

A

Peripheral arteries vasodilation

42
Q

What are the signs and symptoms of chronic hypercapnia?

A

Increased plasma bicarbonate ion concentration

43
Q

Why is there increased plasma bicarbonate ion concentration with chronic hypercapnia?

A

Kidneys reabsorb more, produce more, excrete fewer bicarbonate ions
to stop the forwards bicarbonate buffer reaction being favoured
pH returns to normal

44
Q

What happens to the response to hypercapnia when it becomes chronic?

A

Central chemoreceptors reset to new high pCO2

don’t respond to it

45
Q

What stimulates increased ventilation with chronic hypoventilation?

A

Low plasma pO2

stimulates peripheral chemoreceptors

46
Q

How is chronic type 2 respiratory failure treated?

A

Controlled oxygen therapy

Monitor pCO2

47
Q

Why is pCO2 monitored when treating chronic type 2 respiratory failure by giving oxygen?

A

Further increase in plasma pCO2

worsened hypercapnia

48
Q

Why does hypercapnia become worse when treating chronic type 2 respiratory failure by giving oxygen?

A

Loss of stimulus to peripheral chemoreceptors to stimulate increased ventilation, alveolar ventilation decreases and worsens hypercapnia

Pulmonary hypoxic vasoconstriction is reversed, increased blood flow to poorly ventilated alveoli, reduced blood flow to better ventilated alveoli

Respiratory system (32 decks)

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