ABG Interpretation

Question 1

Normal values for pH?

Answer 1

7.35-7.45

Question 2

Normal values for pH?

Answer 2

7.35-7.45

Question 3

Normal values for pCO2?

Answer 3

4.5-6.0 kPa

Question 4

Normal values for pO2?

Answer 4

11-13 kPa

Question 5

Normal values for HCO3?

Answer 5

22-25 mmol/L

Question 6

Normal values for base excess?

Answer 6

-2 to +2

Question 7

Normal values for lactate?

Question 8

Normal values for SaO2?

Answer 8

> 95%

Question 9

Steps 1-5 in interpreting ABG?

Answer 9

1. Assess oxygenation?
2. Determine pH status
3. Determine respiratory component (PaCO2)
4. Determine metabolic component (HCO3-)
5. Combine (compensation)

Question 10

pH low, PaCO2 high?

Answer 10

Respiratory acidosis

Question 11

pH high, PaCO2 low?

Answer 11

Respiratory alkalosis

Question 12

pH low, HCO3- low?

Answer 12

Metabolic acidosis

Question 13

pH high, HCO3- high

Answer 13

Metabolic alkalosis

Question 14

How can acidosis be compensated for?

Answer 14

Respiratory - increased RR to blow off CO2 (results in reduced CO2)
Metabolic - increased bicarb production by kidney (high bicarb)

Question 15

Causes of respiratory acidosis?

Answer 15

Hypoventilation in:

• Lung disease (COPD, asthma, pulmonary oedema)
• CNS depression
• Mechanical lung dysfunction (obesity, gullian barré, myasthenia gravis)

Question 16

Causes of respiratory acidosis?

Answer 16

Hypoventilation in:

• Lung disease (COPD, asthma, pulmonary oedema)
• CNS depression
• Mechanical lung dysfunction (obesity, gullian barré, myasthenia gravis)

Question 17

Normal values for pCO2?

Answer 17

4.5-6.0 kPa

Question 18

Normal values for pO2?

Answer 18

11-13 kPa

Question 19

Normal values for HCO3?

Answer 19

22-25 mmol/L

Question 20

Normal values for base excess?

Answer 20

-2 to +2

Question 21

Normal values for lactate?

Question 22

Normal values for SaO2?

Answer 22

> 95%

Question 23

Steps 1-5 in interpreting ABG?

Answer 23

1. Assess oxygenation?
2. Determine pH status
3. Determine respiratory component (PaCO2)
4. Determine metabolic component (HCO3-)
5. Combine (compensation)

Question 24

pH low, PaCO2 high?

Answer 24

Respiratory acidosis

Question 25

pH high, PaCO2 low?

Answer 25

Respiratory alkalosis

Question 26

pH low, HCO3- low?

Answer 26

Metabolic acidosis

Question 27

pH high, HCO3- high

Answer 27

Metabolic alkalosis

Question 28

How can acidosis be compensated for?

Answer 28

Respiratory - increased RR to blow off CO2 (results in reduced CO2) Metabolic - increased bicarb production by kidney (high bicarb)

Question 29

How can alkalosis be compensated for?

Answer 29

Respiratory - decreasing resp rate to retain CO2 (high CO2) | Metabolic - decreasing bicarb production by kidney (low HCO3-)

Question 30

Causes of respiratory acidosis?

Answer 30

Hypoventilation in: - Lung disease (COPD, asthma, pulmonary oedema) - CNS depression - Mechanical lung dysfunction (obesity, gullian barré, myasthenia gravis)

Question 31

Causes of respiratory alkalosis?

Answer 31

Hyperventilation in: - Anxiety - Hypoxia - Acute pulmonary insult (PE, pneumonia, asthma attack, pulmonary oedema)

Question 32

Causes of metabolic acidosis?

Answer 32

CHECK ANION GAP = (Na+ + K+)-(Cl- + HCO3-) Normal = 3-12 ``` Increased = new acid added to body (lactic acidosis, DKA, sepsis, aspirin OD) Normal = retaining H+ (renal tubular acidosis, Addison's) or losing HCO3- (diarrhoea) ```

Question 33

Causes of metabolic alkalosis?

Answer 33

Acid loss in: - Chloride responsive: vomiting, diuretics, corticosteroids - Chloride resistant: any hyperaldosterone state (Cushing's, hypokalaemia)

Question 34

Pathophysiology behind type 1 respiratory failure?

Answer 34

Caused by V/Q mismatch: - Low V/Q = areas of lung are perfused with deoxygenated blood but not ventilated with O2 (i.e. airway obstruction - mucus plug in asthma/COPD, airway collapse in emphysema) - High V/Q = areas of lungs venilated with oxygen but not perfused with deoxygenated blood (i.e. block in blood flow - PE)

Question 35

Cause of type 2 respiratory failure?

Answer 35

Alveolar hypoventilation - oxygen cannot get in and CO2 cannot get out. Obstructive lung diseases, restrictive lung diseases, decreased respiratory drive, neuromuscular disease, thoracic wall disease.