Week 5 - Hypoxia

Question 1

What is hypoxia?

Answer 1

Oxygen deficiency at tissue level

Question 2

What is hypoxaemic hypoxia?

Answer 2

Not enough oxygen is getting into the lung and pulmonary capillaries
Poor oxygenation in lungs
Low pO2 and oxygen saturation

Question 3

What is anaemic hypoxia?

Answer 3

Normal pO2 but insufficient haemoglobin to carry it

Question 4

What is stagnant/circulatory hypoxia?

Answer 4

Reduced delivery of oxygen due to poor perfusion

Could be global or local

Question 5

What is cytoxic hypoxia?

Answer 5

Oxygen delivery is adequate but tissues unable to utilise it e.g. Cyanide poisoning

Question 6

What are the features of respiratory failure?

Answer 6

Not enough oxygen enters the blood

Not enough carbon dioxide leaves the blood

Question 7

At what level of oxygen saturation does tissue damage occur?

Answer 7

<90% (<8 kPa pO2)

Question 8

What is type 1 respiratory failure?

Answer 8

pO2 of arterial blood <8 kPa
Oxygen saturation <90%
pCO2 normal or low

Question 9

What is type 2 respiratory failure?

Answer 9

pO2 in arterial blood <8 kPa
Oxygen saturation <90%
pCO2 >6.4 kPa (high)

Question 10

How do we measure oxygen in blood?

Answer 10

Pulse oximeter

Arterial blood gas analysis

Question 11

What does a pulse lximeter show?

Answer 11

Oxygen saturation of haemoglobin in arterial blood

Question 12

What are the mechanisms of type 2 respiratory failure?

Answer 12

Ventilatory failure - unable to move sufficient air in and out if lungs

Question 13

What are the mechanisms of type 1 respiratory failure?

Answer 13

Poor diffusion across alveolar membrane and/or mismatching of ventilation and perfusion

Question 14

What are some causes of type 2 respiratory failure/ventilatory failure?

Answer 14

Opiates
Trauma
Myasthenia gravis
Myopathy
Severe obesity
Pneumothorax
Large pleural effusions
Respiratory distress of newborn
Ling fibrosis
Late COPD

Question 15

What is kyphoscoliosis?

Answer 15

Increase in anteroposterior and lateral curvature of spine

Question 16

What is flail segment?

Answer 16

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

Question 17

What are the acute effects of type 2 respiratory failure?

Answer 17

pCO2 rises
pO2 falls
Central chemoreceptors stimulated
Breathlessness (cant completely compensate)
Respiratory acidosis

Question 18

What factors effect gas exchange?

Answer 18

Thickness of the membrane is increased (lung fibrosis)

Available surface area reduced (emphysema)

Question 19

How doe diffusion impairments affect partial pressures?

Answer 19

pO2 low

pCO2 normal or low because CO2 is more soluble than O2 so diffusion is less affected

Question 20

What is the consequence of low pO2?

Answer 20

Hypoxia stimulates peripheral chemoreceptors resulting in hypoventilation which further increases CO2 removal

Question 21

What is ventilation perfusion ratio?

Answer 21

Alveolar ventilation/lung perfusion (same as cardiac output)

Is ideally 1

Question 22

What is ventilation perfusion mismatching?

Answer 22

Imbalance between alveolar ventilation and alveolar blood flow

Question 23

What happens when ventilation perfusion ratio is <1?

Answer 23

Alveolar pO2 falls and pCO2 rises