Causes Of Hypoxaemia And Hypercapnia

Question 1

What causes insufficient ventilation?

Answer 1

Obstruction of airways or failure to breathe adequately

Question 2

What causes insufficient gas exchange?

Answer 2

Exchange surface dysfunction or VQ mismatch

Question 3

What are the four causes of hypoxaemia?

Answer 3

Insufficient ventilation, insufficient gas exchange, insufficient oxygen carrying capacity and insufficient oxygen in the atmosphere

Question 4

What defines respiratory failure?

Answer 4

When PaO2 < 8kPa when breathing air at sea level

Question 5

What is the cause of type 1 respiratory failure?

Answer 5

Decreased oxygenation

Question 6

What is the cause of type 2 respiratory failure?

Answer 6

Decreased ventilation

Question 7

What is the PaO2 in type 1 respiratory failure?

Answer 7

Decreased

Question 8

What is the PaO2 in type 2 respiratory failure?

Answer 8

Decreased

Question 9

What is the PAO2 in type 1 respiratory failure?

Answer 9

Normal

Question 10

What is the PAO2 in type 2 respiratory failure?

Answer 10

Decreased

Question 11

What is the PaCO2 in type 1 respiratory failure?

Answer 11

Normal

Question 12

What is the PaCO2 in type 2 respiratory failure?

Answer 12

Increased

Question 13

What is the pH in type 1 respiratory failure?

Answer 13

Normal

Question 14

What is the pH in type 2 respiratory failure?

Answer 14

Decreased

Question 15

What is PAO2?

Answer 15

Oxygen pressure in the alveoli

Question 16

What is PaO2?

Answer 16

Arterial oxygen concentration

Question 17

What does it mean if there’s insufficient oxygen in the atmosphere?

Answer 17

Less O2 in atmosphere -> less O2 in alveoli so less arterial O2

Question 18

What are the two types of hypoventilation?

Answer 18

Airway obstruction due to physical blockade or problems with initiation or mechanics of breathing

Question 19

Give examples of airway obstruction hypoventilation

Answer 19

• Asphyxia, choking
• smooth muscle constriction
• excess mucus secretions
• obstructive sleep apnoea
• bronchial obstruction (asthma, chronic bronchitis, cystic fibrosis)

Question 20

What causes the other type of hypoventilation (not airway obstruction)?

Answer 20

• Drug (opioid) overdose
• stroke
• neuromuscular disease (muscular dystrophy, motor neurone disease)
• issues with lung mechanics (COPD, pulmonary fibrosis, NRDS, pneumothorax)

Question 21

What causes oxygenation problems?

Answer 21

V/Q mismatch

Question 22

What is the dead space effect?

Answer 22

Reduced perfusion of lung regions increases V/Q ratio

Question 23

What are the effects of the dead space effect?

Answer 23

Heart failure, blocked vessels and loss /damage of capillaries

Question 24

What is the shunt effect?

Answer 24

Reduced ventilation or limited diffusion, causing a decrease in V/Q ratio

Question 25

Give some diseases where the shunt effect happens

Answer 25

Pneumonia atelectasis (Collapsed lung) Respiratory distress syndrome

Question 26

Give some examples of oxygen transport disorders

Answer 26

Anaemia (blood loss or Hb) Iron deficiency (decreased production) Haemorrhage (increased loss) Carbon monoxide poisoning (CO prevents O2-Hb binding

Question 27

What are the 6 clinical signs of respiratory distress?

Answer 27

``` Tachypnoea, dyspnoea Tachycardia Laboured breathing, audible lung sounds Tiredness, loss of consciousness Fatigue Cyanosis ```

Question 28

What are the clinical effects of insufficient O2 supply?

Answer 28

Dyspnoea, cyanosis, fatigue, coma, seizure

Question 29

What is dyspnoea?

Answer 29

Shortness of breath

Question 30

What are the effects of acute insufficient O2 supply?

Answer 30

Hypoxaemia -> tissue hypoxia -> organ failure -> death

Question 31

What are the effects of chronic insufficient O2 supply?

Answer 31

Polycythaemia, hypoxic pulmonary vasoconstriction -> pulmonary heart failure

Question 32

What is Polycythaemia?

Answer 32

Increased Hb concentration in blood

Question 33

What are the clinical signs of insufficient carbon dioxide removal?

Answer 33

Dyspnoea, confusion, seizure, unconsciousness

Question 34

What is the pathway of insufficient CO2 removal?

Answer 34

Hypercapnia ->acidosis ->organ failure + cardiac arrhythmia -> death