ABG Interpretation Flashcards
Normal values for pH?
7.35-7.45
Normal values for pH?
7.35-7.45
Normal values for pCO2?
4.5-6.0 kPa
Normal values for pO2?
11-13 kPa
Normal values for HCO3?
22-25 mmol/L
Normal values for base excess?
-2 to +2
Normal values for lactate?
Normal values for SaO2?
> 95%
Steps 1-5 in interpreting ABG?
- Assess oxygenation?
- Determine pH status
- Determine respiratory component (PaCO2)
- Determine metabolic component (HCO3-)
- Combine (compensation)
pH low, PaCO2 high?
Respiratory acidosis
pH high, PaCO2 low?
Respiratory alkalosis
pH low, HCO3- low?
Metabolic acidosis
pH high, HCO3- high
Metabolic alkalosis
How can acidosis be compensated for?
Respiratory - increased RR to blow off CO2 (results in reduced CO2)
Metabolic - increased bicarb production by kidney (high bicarb)
Causes of respiratory acidosis?
Hypoventilation in:
- Lung disease (COPD, asthma, pulmonary oedema)
- CNS depression
- Mechanical lung dysfunction (obesity, gullian barré, myasthenia gravis)
Causes of respiratory acidosis?
Hypoventilation in:
- Lung disease (COPD, asthma, pulmonary oedema)
- CNS depression
- Mechanical lung dysfunction (obesity, gullian barré, myasthenia gravis)
Normal values for pCO2?
4.5-6.0 kPa
Normal values for pO2?
11-13 kPa
Normal values for HCO3?
22-25 mmol/L
Normal values for base excess?
-2 to +2
Normal values for lactate?
Normal values for SaO2?
> 95%
Steps 1-5 in interpreting ABG?
- Assess oxygenation?
- Determine pH status
- Determine respiratory component (PaCO2)
- Determine metabolic component (HCO3-)
- Combine (compensation)
pH low, PaCO2 high?
Respiratory acidosis
pH high, PaCO2 low?
Respiratory alkalosis
pH low, HCO3- low?
Metabolic acidosis
pH high, HCO3- high
Metabolic alkalosis
How can acidosis be compensated for?
Respiratory - increased RR to blow off CO2 (results in reduced CO2)
Metabolic - increased bicarb production by kidney (high bicarb)
How can alkalosis be compensated for?
Respiratory - decreasing resp rate to retain CO2 (high CO2)
Metabolic - decreasing bicarb production by kidney (low HCO3-)
Causes of respiratory acidosis?
Hypoventilation in:
- Lung disease (COPD, asthma, pulmonary oedema)
- CNS depression
- Mechanical lung dysfunction (obesity, gullian barré, myasthenia gravis)
Causes of respiratory alkalosis?
Hyperventilation in:
- Anxiety
- Hypoxia
- Acute pulmonary insult (PE, pneumonia, asthma attack, pulmonary oedema)
Causes of metabolic acidosis?
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)
Causes of metabolic alkalosis?
Acid loss in:
- Chloride responsive: vomiting, diuretics, corticosteroids
- Chloride resistant: any hyperaldosterone state (Cushing’s, hypokalaemia)
Pathophysiology behind type 1 respiratory failure?
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)
Cause of type 2 respiratory failure?
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.
