Respi week: Arterial Blood Gases

Question 1

List indicators for starting oxygen therapy for acute cases

Answer 1

• Hypoxia
• Post-operation
• Pneumothorax
• Pulmonary embolism
• Severe sepsis
• Asthma/COPD

Question 2

List indicators for starting oxygen therapy for chronic cases

Answer 2

• COPD
• Cystic fibrosis
• Malignancy
• Interstitial lung disease e.g. pulmonary fibrosis

Question 3

List oxygen delivery methods from low to high rate

Answer 3

Low to high:

1. Nasal cannula
2. Simple Face mask
3. Non-rebreather mask (for acute situations)

+ Venturi system for COPD patients (ensures accurate O2 delivery)

Question 4

Difference between Type 1 and Type 2 respiratory failure

Answer 4

Type 1: Hypoxia + normal pCO2

Type 2: Hypoxia + high pCO2

Question 5

In what types of patients does one see Type 2 respiratory failure

Answer 5

Commonly: COPD

Rare: severe pneumonia, heart failure

Question 6

What are the normal ABG values for the following:

1. pH
2. PaO2
3. PaCO2
4. HCO3
5. Base excess
6. Sats

Answer 6

1. pH: 7.35-7.45
2. PaO2: >11kPA
3. PaCO2: 4.7-6.0kPA
4. HCO3: 21-28 mmol/L
5. Base excess: -2 to +2
6. Sats: >95%

Question 7

Causes of respiratory acidosis

Answer 7

HYPOVENTILATION

• COPD, asthma
• drugs which depress respiration
• CNS trauma
• toxins
• MND

Question 8

Causes of respiratory alkalosis

Answer 8

HYPERVENTILATION

• panic attack
• asthma attack
• pregnancy (well-compensated_
• chronic liver disease
• head injury
• salicylate overdose

Question 9

Causes of metabolic acidosis

Answer 9

INCREASED ACID PRODUCTION/RETENTION or DECREASED HCO3

• diabetic ketoacidosis
• lactic acidosis (may be caused by metformin)
• renal tubular acidosis
• hyperkalemia (causes decreased renal acid excretion)
• diarrhoea (HCO3 loss)

Question 10

Causes of metabolic alkalosis

Answer 10

INCREASED ACID LOSS

• vomit
• hypokalemia (increased renal acid excretion)
• diuretics