Enter arterial blood gas values to quickly identify acid-base imbalances. Get interpretation of the primary disorder, compensation status, and oxygenation assessment.
Normal: 7.35 – 7.45
Normal: 35 – 45
Normal: 22 – 26
Normal: 80 – 100
Primary Disorder
Normal
Compensation
No acid-base disturbance
Oxygenation
Normal oxygenation
Criteria: pH < 7.35, HCO3 < 22
Mechanism: Excess acid production or bicarbonate loss
Common causes: DKA, lactic acidosis, renal failure, diarrhea
Criteria: pH < 7.35, PaCO2 > 45
Mechanism: Inadequate CO2 elimination
Common causes: COPD, hypoventilation, airway obstruction
Criteria: pH > 7.45, HCO3 > 26
Mechanism: Excess bicarbonate or acid loss
Common causes: Vomiting, diuretics, antacid overuse
Criteria: pH > 7.45, PaCO2 < 35
Mechanism: Excessive CO2 elimination
Common causes: Hyperventilation, anxiety, PE, sepsis
All acid-base parameters are within normal limits. No compensation is required.
Arterial blood gas analysis is a critical diagnostic tool used to evaluate a patient's oxygenation, ventilation, and acid-base status. The four key values — pH, PaCO₂, HCO₃⁻, and PaO₂ — work together to paint a picture of respiratory and metabolic function. Systematic interpretation helps nurses and clinicians quickly identify life-threatening conditions like respiratory failure, diabetic ketoacidosis, or severe sepsis.
Normal arterial blood gas values are: pH 7.35–7.45, PaCO₂ 35–45 mmHg, HCO₃⁻ 22–26 mEq/L, and PaO₂ 80–100 mmHg. Values outside these ranges indicate acid-base disturbances or oxygenation problems.
First look at the pH: below 7.35 is acidosis, above 7.45 is alkalosis. Then determine the cause: if PaCO₂ is abnormal and matches the pH direction (high CO₂ with low pH), it is respiratory. If HCO₃⁻ is abnormal and matches the pH direction (low HCO₃⁻ with low pH), it is metabolic.
Compensation occurs when the body tries to normalize the pH by adjusting the system opposite to the primary disorder. In respiratory disorders, the kidneys compensate by retaining or excreting HCO₃⁻. In metabolic disorders, the lungs compensate by adjusting the respiratory rate to change CO₂ levels.
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