Episode Notes

What You’ll Learn

The 5 ABG parts you must know cold

Three proven interpretation methods (4-step, ROME, Tic-Tac-Toe)

How to spot respiratory vs. metabolic problems fast

Compensation (uncompensated, partial, full) and what it tells you about timing

Nursing priorities for each imbalance (what to do now vs. what to fix next)

Key ABG Components and “Normal” Anchors

pH: 7.35–7.45 (acidic vs. alkaline)

CO2: 35–45 (respiratory acid; high = retention, low = blowing off)

Bicarb: 22–26 (metabolic base)

Oxygen: 80–100 (oxygenation; interpret separately from acid–base)

Base excess: −2 to +2 (overall base deficit/excess)

The 3 Methods You Can Trust

1) 4-Step Systematic

pH: low = acidosis, high = alkalosis

CO2: opposite pH → respiratory

Bicarb: same direction as pH → metabolic

Decide compensation (none, partial, full)

2) ROME
Respiratory Opposite, Metabolic Equal

pH high + CO2 low → Respiratory Alkalosis

pH low + CO2 high → Respiratory Acidosis

pH high + bicarb high → Metabolic Alkalosis

pH low + bicarb low → Metabolic Acidosis

3) Tic-Tac-Toe (Visual Grid: Acid | Normal | Base)

Place pH, CO2, bicarb in their columns

Two in a row = primary imbalance; the third value shows compensation

The 4 Acid–Base Imbalances at a Glance

Respiratory Acidosis: pH low, CO2 high

Common causes: hypoventilation (COPD flare, opioids, pneumonia, asthma)

Clues: somnolence, confusion, dyspnea

Priority: airway and ventilation (suction, bronchodilators, BiPAP, intubation if needed)

Respiratory Alkalosis: pH high, CO2 low

Causes: hyperventilation (anxiety, pain, fever, early sepsis)

Clues: dizziness, tingling, lightheadedness

Priority: treat the trigger (calm environment, pain/fever control, guided breathing)

Metabolic Acidosis: pH low, bicarb low

Causes: DKA, lactic acidosis, diarrhea, renal failure

Clues: fatigue, confusion, Kussmaul breathing

Priority: treat the cause (fluids, insulin for DKA, shock management), monitor potassium

Metabolic Alkalosis: pH high, bicarb high

Causes: vomiting, NG suction, diuretics, excessive base intake

Clues: muscle cramps, arrhythmias

Priority: stop the loss or over-base, replace electrolytes (especially potassium, chloride)

Compensation — What It Tells You About Time

Uncompensated: primary system abnormal; pH abnormal

Partially compensated: both systems abnormal; pH still abnormal

Fully compensated: both systems abnormal; pH back in range

A fully compensated respiratory acidosis usually means a chronic issue (like COPD)

Nursing Pearls

Always read in order: pH → CO2 → bicarb

Never interpret an ABG in isolation — check the patient first

Think beyond the label: cause and correction

Check oxygen last: it affects stability but not the acid–base label itself

Quick Practice (from the Transcript Flow)

pH 7.30, CO2 60, bicarb 30 → partially compensated respiratory acidosis

pH 7.20, CO2 25, bicarb 12 → partially compensated metabolic acidosis

pH 7.50, CO2 25, bicarb 23 → uncompensated respiratory alkalosis

Need to reach out? Send an email to Brooke at [email protected]