Interpretation of ABG (Arterial blood gas) Analysis Report

Question 1

Normal ABG report​

Answer 1

• pCO₂: 4.5 to 6Kpa (35 to 45mmHg)
• pO₂: 10-14 Kpa (80-100mmHg)
• PH: 7.35 to 7.45
• HCO₃^-: 21-28mmHg (22-26mmHg, to be exact)

Question 2

Interpretation of ABG report

Answer 2

Interpretation of ABG results: [OHCM]

1^st step: check pH

• pH <7.35 >>> acidosis
• pH >7.35 >>> alkalosis

2^nd step: check pCO₂ [pCO₂ high is acidic, and pCO₂ low is alkali]

• If it says the same as of pH >>> respiratory problem
• If both says acidic >>> respiratory acidosis (pH <7.35, pCO₂ >45mmHg or 6kPa)
• If both says alkali >>> respiratory alkalosis (pH >7.35, pCO₂ <35mmHg or 4kPa)
• If it says opposite of pH >>> metabolic problem

3^rd step: check HCO₃ [High HCO₃ is alkali, and low is acidic]

• If it says same as of pH >>> metabolic problem
• If both says acidic >>> metabolic acidosis
• If both says alkali >>> metabolic alkalosis

[Now, we already have the clinical condition: respiratory/metabolic acidosis/alkalosis]

4^th step: If there is any compensation (by pCO₂ or HCO₃)

• If CO₂ or HCO₃ tries to compensate >>> Compensatory
• Compensatory but pH is still abnormal >>> partially compensated
• Compensatory & pH goes back to normal >>> fully compensated)

5^th step: Only if it is respiratory alkalosis/acidosis >>> Check pO₂ (whether it is normal); given the FiO₂ (fraction of inspired oxygen)

• If low pO₂ >>> respiratory failure
• If low pO₂ + low/normal pCO₂ >>> type 1 R.F (usually with for respiratory alkalosis)
• If low pO₂ + high pCO₂ >>> type 2 R.F (usually with respiratory acidosis)

6^th step: Only If it is metabolic acidosis >>> calculate anion gap [(Na + K) – (HCO₃ + Cl)]

• If >18mmol/L >>> raised anion gap
• If 10 to 18mmol/L >>> Normal anion gap
• If <10mmol/L >>> Reduced anion gap

[Roughly if cl level is given in the question >>> indicates it’s needed to calculate anion gap]

Question 3

Interpretation of compensation from ABG report

Answer 3

Check If there is any compensation (by pCO₂ or HCO₃)

• If CO₂ or HCO₃ tries to compensate >>> Compensatory
• Compensatory but pH is still abnormal >>> partially compensated
• Compensatory & pH goes back to normal >>> fully compensated)

Question 4

pH: Low (<7.35)

HCO₃: Low (<22mmol/L)

pCO₂: Normal (4.5-6kPa = 35-45mmHg)

>>> Dx?

Answer 4

Metabolic acidosis (uncompensated)

Question 5

pH: Low (<7.35)

HCO₃: Low (<22mmol/L)

CO₂: Low (<4.5kPa or <35mmHg)

>>> Dx

Answer 5

Partially compensated Metabolic acidosis

Question 6

pH: Normal (7.35 to 7.45)

HCO3: Low (<22mmol/L)

pCO₃: Low (<4.5kPa or <35mmHg)

>>> Dx

Answer 6

Fully compensated metabolic acidosis

Question 7

pH: High (>7.45)

HCO₃: High (>26mmol/L)

pCO₂: Normal (4.5 to 6kPa or 35-45mmHg)

>>> Dx

Answer 7

Metabolic alkalosis (uncompensated)

Question 8

pH: High (>7.45)

HCO₃: High (>26mmol/L)

pCO₂: High (>6kPa or <45mmHg)

>>> Dx

Answer 8

Partially compensated Metabolic alkalosis

Question 9

pH: Normal (7.35 to 7.45)

HCO₃: High (>26mmol/L)

pCO₂: High (>6kPa or >45mmHg)

>>> Dx

Answer 9

Fully compensated metabolic alkalosis

Question 10

Interpretation of anion gap from the electrolytes report

Answer 10

Only If it is metabolic acidosis >>> calculate anion gap [(Na + K) – (HCO3 + Cl)]

• If >18mmol/L >>> raised anion gap
• If 10 to 18mmol/L >>> Normal anion gap
• If <10mmol/L >>> Reduced anion gap

[Roughly if cl level is given in the question >>> indicates it’s needed to calculate anion gap]

Question 11

pH: Low (<7.35)

HCO₃: Normal (22-26mmol/L)

pCO₂: High (>6kPa or >45mmHg)

>>> Dx

Answer 11

Respiratory acidosis (uncompensated)

Question 12

pH: Low (<7.35)

HCO₃: High (>26mmol/L)

pCO₂: High (>6kPa or >45mmHg)

>>> Dx

Answer 12

Partially compensated Respiratory acidosis

Question 13

pH: Normal (7.35 to 7.45)

HCO₃: High (>26mmol/L)

pCO₂: High (>6kPa or >45mmHg)

>>> Dx

Answer 13

Fully compensated Respiratory acidosis

Question 14

pH: Low (<7.35)

HCO₃: Normal/High

pCO₂: High (>6kPa or >45mmHg)

pO₂: Low (<10kPa or <80mmHg)

>>> Dx

Answer 14

Respiratory acidosis + type-II respiratory failure

(HCO₃ normal >>> only R.acidosis; HCO₃ high >>> compensatory)

Question 15

pH: High (>7.45)

HCO₃: Normal (22-26mmol/L)

pCO₂: Low (<4.5kPa or <35mmHg)

>>> Dx

Answer 15

Respiratory alkalosis (uncompensated)

Question 16

pH: High (>7.45)

HCO₃: Low (<22mmol/L)

pCO₂: Low (<4.5kPa or <35mmHg)

>>> Dx

Answer 16

Partially compensated Respiratory alkalosis

Question 17

pH: Normal (7.35-7.45)

HCO₃: Low (<22mmol/L)

pCO₂: Low (<4.5kPa or <35mmHg)

>>> Dx

Answer 17

Fully compensated Respiratory alkalosis

Question 18

pH: High (>7.45)

HCO₃: Normal/Low

pCO₂: Low (<4.5kPa or <35mmHg)

pO₂: Low (<10kPa or <80mmHg)

>>> Dx

Answer 18

Respiratory alkalosis with type I respiratory failure

(Normal HCO₃ >> only respi. alkalosis; Low HCO₃ >> compensatory respi. alkalosis)

Question 19

(pH: high/normal

HCO₃: normal/low/any level)

pCO₂: Normal (4.5-6kPa or 35-45mmHg)

pO₂: Low (<10kPa or <80mmHg)

>>> Dx

Answer 19

Type 1 respiratory failure

Question 20

Interpretation of respiratory failure from ABG report

Answer 20

Only if it is respiratory alkalosis/acidosis >>> Check pO₂ (whether it is normal); given the FiO₂ (fraction of inspired oxygen)

• If low pO₂ >>> respiratory failure
• If low pO₂ + low/normal pCO₂ >>> type 1 R.F (usually with for respiratory alkalosis)
• If low pO₂ + high pCO₂ >>> type 2 R.F (usually with respiratory acidosis)

Question 21

pO₂ low (<10kPa or <80mmHg) +

pCO₂ (<4.5kPa or <35mmHg) >>> Type of respiratory failure

Answer 21

Type I respiratory failure

Question 22

pO₂ low (<10kPa or <80mmHg) +

pCO₂ (Normal: 4.5 to 6kPa or 35 to 45mmHg) >>> Type of respiratory failure

Answer 22

Type 1 respiratory failure

Question 23

pO₂ low (<10kPa or <80mmHg) +

pCO₂ (>6kPa or >45mmHg) >>> Type of respiratory failure

Answer 23

Type II respiratory failure