Normal values:

• pH: 7.35 – 7.45
• PaCO2: 35 – 45
• HCO3: 22 – 26

Acidosis: pH < 7.35

Alkalosis: pH > 7.45

Respiratory acidosis:

• Findings: Low pH, high PaCO2
• Causes: Sedative overdose, hypoventilation, atelectasis.
• Pathophysiology: CO2 retention from hypoventilation.
• Compensation: HCO3 retention by kidneys.

Respiratory alkalosis:

• Findings: High pH, low PaCO2
• Causes: Hyperventilation.
• Pathophysiology: Increased CO2 excretion from hyperventilation.
• Compensation: HCO3 excretion by kidneys.

Metabolic acidosis:

• Findings: Low pH, high HCO3
• Causes: DKA, renal failure, severe diarrhea
• Pathophysiology: Inability to excrete acid or loss of base
• Compensation: CO2 excretion by lungs.

Metabolic alkalosis:

• Findings: High pH, high HCO3
• Causes: Severe vomiting, gastric suctioning, high NAHCO3 intake.
• Pathophysiology: Loss of strong acid or gain of base
• Compensation: CO2 retention by lungs.