ABG ANALYSIS TOOL

Easy Doctor's Tool

ABG ANALYSIS TOOL

Enter ABG values

Normal Reference Range :
• pH 7.35–7.45 • PaCO₂ 35–45 mmHg • HCO₃⁻ 22–26 mmol/L

PaCO₂ (mmHg)

HCO₃⁻ (mmol/L)

PaO₂ (mmHg)

FiO₂ (as decimal) 0.21 in room air

Age (yrs)

Na⁺ (mmol/L)

Cl⁻ (mmol/L)

Disclaimer : The ABG Interpret Tool is a decision support tool for healthcare professionals. It should never replace overall comprehensive patient assessment or the clinical judgment of a doctor anyplace and anytime.

Result

of ABG

pH Status

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Primary Disorder

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Compensation

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Anion Gap & Δ-gap

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Oxygenation & A–a

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P/F ratio (PaO₂/FiO₂)

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Final ABG Interpretation

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HOW TO INTERPRET ABG

1) pH -> direction (acidemia/alkalemia).
2) Use ROME to identify primary disorder.
3) Use Winter's formula for metabolic acidosis.
4) For respiratory disorders compare acute vs chronic HCO₃ change.
5) Calculate AG & Δ-gap to identify mixed metabolic processes.
6) Assess oxygenation A–a gradient and
7) P/F ratio for ARDS classification.
8) FiO₂ defaults to 0.21 (in room air) FiO2 varies if patients are on O₂, NRBM, HFNC or in Ventilator.So put Fio2 accordingly

➟ BICARBONATE low = ACIDOSIS
➟ BICARBONATE high = ALKALOSIS

➟ PaCo2 High = ACIDOSIS : Hypoventilation
➟ PaCo2 Low = ALKALOSIS : Hyperventilation

METABOLIC DISORDERS

Acidosis (Check AG)	High AG: Lactate, DKA, Renal Failure, Toxins Normal AG: Diarrhea, RTA, Saline Overload
Alkalosis (Vol. Status)	Vomiting, Diuretics, Hypokalemia

RESPIRATORY DISORDERS

Acidosis	Assess: Airway and Ventilation support
Alkalosis	Look for Triggers: Pain, Anxiety, Sepsis, Hypoxia, PE

P/F RATIO & OXYGENATION

P/F > 300	Observe
200 – 300	Oxygen Supplementation
100 – 200	NIV / HFNC (If GCS is Good)
< 100	Intubation Consideration

ROME Logic for Acid-Base Balance

System	Logic (pH vs Parameter)
RESPIRATORY (PaCO₂)	OPPOSITE Direction ↑CO₂ = ↓pH (Acidosis) ↓CO₂ = ↑pH (Alkalosis) e.g., COPD, Hyperventilation
METABOLIC (HCO₃⁻)	EQUAL Direction ↑HCO₃ = ↑pH (Alkalosis) ↓HCO₃ = ↓pH (Acidosis) e.g., DKA, Severe Vomiting

Parameter	Interpretation
HCO₃⁻ Low ↓	Metabolic Acidosis Examples: DKA, Renal Failure, Lactic Acidosis, Diarrhea.
HCO₃⁻ High ↑	Metabolic Alkalosis Examples: Severe Vomiting, Gastric Suction, Diuretic use.
PaCO₂ High ↑	Respiratory Acidosis Examples: COPD, Opioid Overdose, Hypoventilation.
PaCO₂ Low ↓	Respiratory Alkalosis Examples: Anxiety, Hyperventilation, Fever, High Altitude.

Acid-Base Compensation

If Primary is...	Body Will...
Met. Acidosis (↓HCO₃)	Blow off CO₂ Hyperventilate (Minutes)
Met. Alkalosis (↑HCO₃)	Retain CO₂ Hypoventilate (Minutes)
Resp. Acidosis (↑CO₂)	Retain HCO₃ Renal Buffer (SLOW)
Resp. Alkalosis (↓CO₂)	Excrete HCO₃ Renal Buffer (SLOW)

Adequate Compensation Formulas

METABOLIC ACIDOSIS (Winter's Formula )

      Expect PaCO₂ = (1.5 × HCO₃) + 8 ± 2
    

METABOLIC ALKALOSIS

      ↑ PaCO₂ = 0.7 × (Measured HCO₃ - 24)
    

RESPIRATORY (Per 10 change in PaCO₂)
Expected change of Bicarbonates

ACIDOSIS:
Acute: +1 HCO₃
Chronic: +4 HCO₃

ALKALOSIS:
Acute: -2 HCO₃
Chronic: - 4 / 5 HCO₃

FiO₂ Estimation Tool

Oxygen Device

Flow (L/min)

FiO₂ result will appear here…