🧬 Interactive Acid-Base Balance
Master ABG interpretation with real-time feedback and interactive patient scenarios
🔬 Interactive ABG Simulator
Adjust the sliders to see how different values affect acid-base balance interpretation:
🎯 Practice Mode
Test your knowledge with randomized scenarios:
📊 Live Interpretation
🎓 Guided Tutorial: From Beginner to Expert
📖 Lesson 1: What is Acid-Base Balance?
Welcome to your journey from beginner to acid-base expert!
Your body is like a finely tuned chemistry lab. The pH of your blood must stay between 7.35-7.45 for your cells to function properly.
🧪 Key Concept: pH Scale
- pH < 7.35: Acidosis (too acidic, life-threatening)
- pH 7.35-7.45: Normal (perfect balance)
- pH > 7.45: Alkalosis (too basic, also dangerous)
Try it yourself: Move the pH slider below and watch what happens!
🏥 Clinical Reality
When a patient's pH goes outside 7.35-7.45, their body immediately activates two backup systems: the lungs and the kidneys. You're about to learn how!
🫁 Lesson 2: Meet Your Body's pH Control Systems
Your body has two main systems working 24/7 to keep pH perfect:
🫁 Respiratory System (Lungs)
Controls: CO₂ (Carbon Dioxide)
Speed: Fast (minutes to hours)
How: Breathing faster = less CO₂ = higher pH
Normal Range: 35-45 mmHg
🩻 Metabolic System (Kidneys)
Controls: HCO₃⁻ (Bicarbonate)
Speed: Slow (hours to days)
How: Keep or dump bicarbonate
Normal Range: 22-26 mEq/L
🎯 The Golden Rule
If one system causes a problem, the other tries to fix it!
- Lungs too slow? → Kidneys compensate
- Kidneys failing? → Lungs compensate
- Both failing? → Medical emergency!
🧠 Memory Trick
"ROME" - Remember this forever!
- Respiratory Opposite (pH and CO₂ go opposite directions)
- Metabolic Equal (pH and HCO₃⁻ go same direction)
📊 Lesson 3: Reading Your First ABG
Now let's interpret a real ABG step by step. Don't worry - we'll do this together!
Patient Case: John, 65 years old with COPD
Step 1: Look at the pH
pH = 7.32. Is this normal, acidic, or basic?
Step 2: Find the Primary Problem
Since we have acidosis, which system is causing it?
• CO₂ = 58 mmHg (normal: 35-45) = HIGH
• HCO₃⁻ = 28 mEq/L (normal: 22-26) = HIGH
Step 3: Check for Compensation
Are the kidneys trying to help?
🏥 What This Means for John
John's COPD lungs can't clear CO₂ well, making his blood acidic. His kidneys are working overtime to help, but haven't fully corrected the pH yet. He needs bronchodilators and possibly ventilation support.
🎯 Lesson 4: Master the Four Patterns
There are only 4 main patterns to learn. Master these and you're 90% there!
🫁 Respiratory Acidosis
Problem: Lungs not working
Causes: COPD, pneumonia, drugs
Compensation: Kidneys keep HCO₃⁻
🫁 Respiratory Alkalosis
Problem: Breathing too fast
Causes: Anxiety, pain, high altitude
Compensation: Kidneys dump HCO₃⁻
🎯 Quick Practice
Can you identify this pattern?
⚖️ Lesson 5: Compensation Mastery
Understanding compensation separates good nurses from great ones. Let's master this!
📏 The Compensation Rules
Rule 1: Compensation Never Overcorrects
If pH starts low, compensation will move it toward normal but never past 7.40
If pH starts high, compensation will move it toward normal but never below 7.40
Rule 2: Respiratory Compensation is Fast
Lungs can change breathing in minutes. Look for compensation within hours.
Rule 3: Metabolic Compensation is Slow
Kidneys take 1-3 days to fully compensate. Be patient!
🧮 Expected Compensation Formulas
Metabolic Acidosis
Winter's Formula:
Expected CO₂ = 1.5 × (HCO₃⁻) + 8 (±2)
If HCO₃⁻ = 16:
Expected CO₂ = 1.5 × 16 + 8 = 32 mmHg
Respiratory Acidosis
Acute: HCO₃⁻ ↑ by 1 for every 10 mmHg ↑ in CO₂
Chronic: HCO₃⁻ ↑ by 4 for every 10 mmHg ↑ in CO₂
🎮 Interactive Compensation Checker
📋 Start here: Click any of the example buttons below to automatically load ABG values and see detailed compensation analysis. This will help you understand how to recognize compensation patterns!
🎯 Learning Goal: After clicking each example, you'll see detailed analysis explaining whether compensation is appropriate, inappropriate, or if it's a mixed disorder. This teaches you to recognize compensation patterns in real clinical scenarios.
Or try your own values:
👆 Click an example button above to see detailed compensation analysis, or enter your own values!
🚨 Lesson 6: Critical Recognition - Save Lives
Some ABGs are medical emergencies. You need to recognize these immediately!
🚨 IMMEDIATE EMERGENCY
- pH < 7.20 or > 7.60
- CO₂ > 70 mmHg (severe respiratory failure)
- HCO₃⁻ < 10 mEq/L (severe acidosis)
Action: Call MD immediately, prepare for intubation/dialysis
⚠️ URGENT ATTENTION
- pH 7.20-7.30 or 7.50-7.60
- Mixed disorders (both systems failing)
- No compensation when expected
Action: Notify MD within 30 minutes, frequent monitoring
☠️ Deadly Mixed Disorders
Mixed Acidosis
pH: 7.18, CO₂: 65, HCO₃⁻: 12
Problem: Both lungs AND kidneys failing
Seen in: Cardiac arrest, severe sepsis
Respiratory Acidosis + Metabolic Acidosis
pH: 7.15, CO₂: 58, HCO₃⁻: 14
Problem: No compensation possible
Seen in: Cardiopulmonary arrest, end-stage disease
🔍 Clinical Assessment Skills
What to Look For
- Breathing pattern (Kussmaul, shallow, fast)
- Mental status (confusion from pH changes)
- Skin color (cyanosis from poor oxygenation)
- Heart rhythm (arrhythmias from electrolyte shifts)
Questions to Ask
- Recent illness or medication changes?
- Vomiting, diarrhea, or poor intake?
- History of lung or kidney disease?
- Drug or alcohol use?
🎓 Lesson 7: Advanced Applications
Now you're ready for advanced concepts that will make you an ABG expert!
🧪 Anion Gap
Helps determine the cause of metabolic acidosis:
Anion Gap = Na⁺ - (Cl⁻ + HCO₃⁻)
Normal: 8-12 mEq/L
High Anion Gap (>12)
MUDPILES: Methanol, Uremia, DKA, Propylene glycol, Iron/Isoniazid, Lactic acidosis, Ethylene glycol, Salicylates
Normal Anion Gap (8-12)
HARDUPS: Hyperalimentation, Acetazolamide, RTA, Diarrhea, Ureteral diversions, Post-hypocapnia, Saline
📊 Base Excess/Deficit
Shows the metabolic component isolated from respiratory effects:
- Base Excess: > +2 = metabolic alkalosis
- Normal: -2 to +2
- Base Deficit: < -2 = metabolic acidosis
🫁 Oxygenation Assessment
PaO₂: 80-100 mmHg (normal)
SaO₂: >95% (normal)
A-a Gradient: Age ÷ 4 + 4 (normal)
Mild Hypoxemia: PaO₂ 60-79 mmHg
Moderate: PaO₂ 40-59 mmHg
Severe: PaO₂ < 40 mmHg
🏥 Expert-Level Scenarios
ICU Patient with Multiple Issues
pH: 7.32, PaCO₂: 28, HCO₃⁻: 14, Na⁺: 140, Cl⁻: 102, PaO₂: 65
🏆 Lesson 8: Final Mastery Test
Congratulations! You've learned everything needed to be an ABG expert. Let's prove it!
🎯 Expert Certification Challenge
Interpret these 5 ABGs correctly to earn your expert badge:
Question 1
pH: 7.48, PaCO₂: 32, HCO₃⁻: 23
Question 2
pH: 7.25, PaCO₂: 55, HCO₃⁻: 23
Question 3
pH: 7.35, PaCO₂: 60, HCO₃⁻: 32
Question 4
pH: 7.20, PaCO₂: 58, HCO₃⁻: 15
Question 5
pH: 7.38, PaCO₂: 30, HCO₃⁻: 17
📚 Step-by-Step ABG Interpretation
Follow these systematic steps to interpret any ABG:
pH < 7.35 = Acidosis
pH > 7.45 = Alkalosis
pH 7.35-7.45 = Normal
Look at PaCO₂ and HCO₃⁻ to see which matches the pH direction (respiratory vs metabolic)
If pH abnormal, does the opposite system try to normalize it? (partial vs complete compensation)
Check PaO₂ (normal 80-100 mmHg) and oxygen saturation for respiratory function
🏥 Practice Scenarios
💡 How to use: Click any scenario card below to automatically load the ABG values into the simulator tab. Then switch to the simulator to practice interpretation!
65-year-old COPD patient with acute exacerbation and CO₂ retention
Type 1 diabetic in DKA with Kussmaul breathing
Young adult with panic attack and hyperventilation
Patient with prolonged vomiting and dehydration
Chronic COPD patient with full renal compensation
Chronic kidney disease with respiratory compensation
ICU patient with respiratory failure and septic shock
Lactic acidosis with maximal respiratory compensation
📊 Reference Values
| Parameter | Normal Range | Acidosis | Alkalosis | Critical Values |
|---|---|---|---|---|
| pH | 7.35-7.45 | < 7.35 | > 7.45 | < 7.20 or > 7.60 |
| PaCO₂ | 35-45 mmHg | > 45 (respiratory) | < 35 (respiratory) | < 20 or > 70 |
| HCO₃⁻ | 22-26 mEq/L | < 22 (metabolic) | > 26 (metabolic) | < 15 or > 40 |
| PaO₂ | 80-100 mmHg | Hypoxemia < 80 | < 60 (respiratory failure) | |
| O₂ Saturation | 95-100% | Hypoxemia < 95% | < 90% | |
⚗️ Advanced Tools
🧮 Anion Gap Calculator
Calculate anion gap to determine causes of metabolic acidosis:
Interpretation:
- Normal (8-12): HARDUPS causes
- High (>12): MUDPILES causes
- Low (<8): Hypoalbuminemia, lab error
📏 Compensation Calculator
Check if respiratory/metabolic compensation is appropriate:
🫁 A-a Gradient Calculator
Assess oxygenation and lung function:
📊 Base Excess Calculator
Determine metabolic component independent of respiratory effects:
Interpretation:
- Normal: -2 to +2 mEq/L
- Base Deficit (< -2): Metabolic acidosis
- Base Excess (> +2): Metabolic alkalosis
🎯 Clinical Decision Support
Get clinical recommendations based on ABG results:
📈 Trend Analysis
Compare serial ABGs to track patient progress:
Previous ABG
Current ABG
⚠️ Important Disclaimer
This educational module is for learning purposes only and should not replace clinical judgment, facility protocols, or provider orders. Normal ranges may vary by laboratory. Always verify critical values, follow your institution's policies for ABG interpretation and patient care, and consult with physicians for treatment decisions.