28/01/2026
CPAP vs BiPAP (NIV)
One pressure vs Two pressures — when to use which?
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✅ CPAP
Continuous Positive Airway Pressure
How it works
• ONE pressure (same on inhale + exhale)
• Splints airway open → improves oxygenation
Best for
• Obstructive Sleep Apnea (OSA) ⭐
• Cardiogenic pulmonary edema (helps oxygenation + reduces preload)
Pros
• Simpler + cheaper
• First-line for most OSA
Limitation
• Not great if patient needs ventilation/CO₂ removal
✅ Quick clue: CPAP = Constant Pressure → Simple OSA
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✅ BiPAP
BiLevel Positive Airway Pressure
How it works (2 pressures)
• IPAP = higher pressure on inhale
• EPAP = lower pressure on exhale
➡️ IPAP − EPAP = Pressure Support = Ventilation (CO₂ out)
Best for (ventilation support)
• COPD exacerbation + hypercapnia (↑CO₂) ⭐
• Obesity hypoventilation
• Neuromuscular weakness (ALS, MG, muscular dystrophy)
• CPAP failure / intolerance (hard to exhale)
Pros
• Easier exhalation
• Better CO₂ clearance
✅ Quick clue: BiPAP = Two pressures → helps CO₂ → complex cases
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🚫 When NOT to use CPAP/BiPAP (Contraindications)
• Can’t protect airway / vomiting / aspiration risk
• Severe altered mental status
• Hemodynamic instability/shock
• Facial trauma / poor mask seal
• Untreated pneumothorax
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1-line exam summary
• CPAP = oxygenation + airway splinting
• BiPAP = ventilation + CO₂ removal