Clinical Skills
Step-by-Step Guide

ABG Interpretation Made Easy: 5 Critical Steps for Nurses

Master Arterial Blood Gas analysis, understand acid-base disorders, and make swift, confident decisions at the bedside.

Primary Target Acid-Base Balance
Clinical Shortcut R.O.M.E. Method
Target Audience Nurses & Students
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Step 01
Acid-Base Foundation

Inspect the pH First

Normal Arterial Range 7.35 – 7.45
Absolute Neutral 7.40
pH < 7.35 • Acidosis

Indicates excess hydrogen ions (H+) or CO2 retention. Watch for lethargy, hypotension, and hyperkalemia.

pH > 7.45 • Alkalosis

Indicates hydrogen depletion or base excess. Watch for neuromuscular excitability, tetany, and hypokalemia.

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Step 02
Respiratory Component

Evaluate the PaCO2 Level

Normal Range 35 – 45 mmHg
Organ Controlled Lungs (Rapid response)
ROME Rule: Respiratory Opposite

• PaCO2 > 45 + Low pH = Respiratory Acidosis (Hypoventilation, COPD, opioid toxicity).
• PaCO2 < 35 + High pH = Respiratory Alkalosis (Hyperventilation, pain, pulmonary embolism).

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Step 03
Metabolic Component

Examine Serum Bicarbonate (HCO3)

Normal Range 22 – 26 mEq/L
Organ Controlled Kidneys (Hours to days)
ROME Rule: Metabolic Equal

• HCO3 < 22 + Low pH = Metabolic Acidosis (DKA, severe diarrhea, renal failure).
• HCO3 > 26 + High pH = Metabolic Alkalosis (NG suctioning, severe vomiting, excess antacids).

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Step 04
Physiologic Defense

Identify Compensation Status

Uncompensated pH abnormal, 1 abnormal
Partially Compensated pH & both abnormal
Fully Compensated pH normal (7.35–7.45)
Clinical Tip for Full Compensation

If pH is within normal limits but both PaCO2 and HCO3 are abnormal, look at 7.40. If pH < 7.40, primary cause was acidosis; if > 7.40, alkalosis.

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Step 05
Bedside Action

Oxygenation & Nursing Interventions

Normal PaO2 80 – 100 mmHg
Normal SaO2 95% – 100%
Nursing Care Priorities

• Airway & Position: Elevate HOB (Semi-Fowler's) to enhance lung expansion.
• Ventilation Check: Verify FiO2 and flow rates.
• SBAR Report: Communicate values promptly to MD.

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Quiz & Review
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